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In preparation for unconditionally passing the
struct tasklet_struct pointer to all tasklet
callbacks, switch to using the new tasklet_setup()
and from_tasklet() to pass the tasklet pointer explicitly.
Signed-off-by: Romain Perier <romain.perier@gmail.com>
Signed-off-by: Allen Pais <allen.lkml@gmail.com>
Link: https://lore.kernel.org/r/20200831103542.305571-2-allen.lkml@gmail.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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'desc' variable is now defined but not used in sf_pdma_donebh_tasklet(),
causing this warning:
drivers/dma/sf-pdma/sf-pdma.c: In function 'sf_pdma_donebh_tasklet':
drivers/dma/sf-pdma/sf-pdma.c:287:23: warning: unused variable 'desc' [-Wunused-variable]
Remove this unused variable
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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The original commit mixed up the forward and completion ring IDs for the
rx flow configuration.
Acked-by: Vinod Koul <vkoul@kernel.org>
Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Fixes: 4927b1ab2047 ("dmaengine: ti: k3-udma: Switch to k3_ringacc_request_rings_pair")
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
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rcar-dmac driver is used on Renesas R-Car Gen{2,3} and Renesas
RZ/G{1,2} SoC's, update the same to reflect the description
for RCAR_DMAC config.
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Chris Paterson <Chris.Paterson2@renesas.com>
Link: https://lore.kernel.org/r/20200911095734.19348-1-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Use separate data for SoC dependent parameters. These parameters depends
on the DMA integration (either in HW or in SYSFW), the DMA controller
itself remains compatible with either the am654 or j721e variant.
j7200 have the same DMA as j721e with different number of channels, which
can be queried from HW, but SYSFW defines different rchan_oes_offset
number for j7200 (0x80) compared to j721e (0x400).
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20200910124329.21206-1-peter.ujfalusi@ti.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Linux 5.9-rc4
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When we got an error from DMA mapping API we convert a negative value
to unsigned long type and hence make user confused:
result #1: 'src mapping error' with src_off=0x19a72 dst_off=0xea len=0xccf4 (18446744073709551604)
Change this to print error codes as signed values.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200907101306.61824-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Since commit f458488425f1 ("amba: Initialize dma_parms for amba
devices"), struct amba_device already provides a dma_parms structure,
so we can save allocating another one.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/c9e58882e33f22f9b0a6d65a5507e24004512148.1599164692.git.robin.murphy@arm.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Since commit 9495b7e92f71 ("driver core: platform: Initialize dma_parms
for platform devices"), struct platform_device already provides a
dma_parms structure, so we can save allocating another one.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/60ac2ef17e242dbf631db29ebde9d64d6df67030.1599164692.git.robin.murphy@arm.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Since commit 9495b7e92f71 ("driver core: platform: Initialize dma_parms
for platform devices"), struct platform_device already provides a
dma_parms structure, so we can save allocating another one.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/011a956183b92a258bf0922385d145ea966dcbea.1599164692.git.robin.murphy@arm.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Since commit 9495b7e92f71 ("driver core: platform: Initialize dma_parms
for platform devices"), struct platform_device already provides a
dma_parms structure, so we can save allocating another one.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/23d40e15af10aad4724a2770ec18b4b28c1b8a71.1599164692.git.robin.murphy@arm.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Since commit 9495b7e92f71 ("driver core: platform: Initialize dma_parms
for platform devices"), struct platform_device already provides a
dma_parms structure, so we can save allocating another one.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/dc0fb6963067b9c799873d761661ed6dce1426ec.1599164692.git.robin.murphy@arm.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Since commit 9495b7e92f71 ("driver core: platform: Initialize dma_parms
for platform devices"), struct platform_device already provides a
dma_parms structure, so we can save allocating another one.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/d9b551dcf712a91860af3c5dd01a31b9b97ac1c5.1599164692.git.robin.murphy@arm.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Since commit 9495b7e92f71 ("driver core: platform: Initialize dma_parms
for platform devices"), struct platform_device already provides a
dma_parms structure, so we can save allocating another one.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/7fad3c60cac2bf4f8dab791f8b6eafae90abc960.1599164692.git.robin.murphy@arm.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Since commit 9495b7e92f71 ("driver core: platform: Initialize dma_parms
for platform devices"), struct platform_device already provides a
dma_parms structure, so we can save allocating another one.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/116927330a4a66aac579ad38ddbc3b538cd9524c.1599164692.git.robin.murphy@arm.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Since commit 9495b7e92f71 ("driver core: platform: Initialize dma_parms
for platform devices"), struct platform_device already provides a
dma_parms structure, so we can save allocating another one.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/9b759e4c9eb37c90a3616d31abe13af6a6dafcd2.1599164692.git.robin.murphy@arm.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Because a callback is called twice when DMA transfer complete
the second callback may be possible to access a freed memory
if the first callback routines perform the dma_release_channel function.
So this patch serialized the callback functions
Signed-off-by: Brad Kim <brad.kim@semifive.com>
Tested-and-reviewed-by: Green Wan <green.wan@sifive.com>
Signed-off-by: Brad Kim <brad.kim@sifive.com>
Link: https://lore.kernel.org/r/20200903111726.3413-1-brad.kim@sifive.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/vkoul/dmaengine
Pull dmaengine fixes from Vinod Koul:
"A couple of core fixes and odd driver fixes for dmaengine subsystem:
Core:
- drop ACPI CSRT table reference after using it
- fix of_dma_router_xlate() error handling
Drivers fixes in idxd, at_hdmac, pl330, dw-edma and jz478"
* tag 'dmaengine-fix-5.9-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/vkoul/dmaengine:
dmaengine: ti: k3-udma: Update rchan_oes_offset for am654 SYSFW ABI 3.0
drivers/dma/dma-jz4780: Fix race condition between probe and irq handler
dmaengine: dw-edma: Fix scatter-gather address calculation
dmaengine: ti: k3-udma: Fix the TR initialization for prep_slave_sg
dmaengine: pl330: Fix burst length if burst size is smaller than bus width
dmaengine: at_hdmac: add missing kfree() call in at_dma_xlate()
dmaengine: at_hdmac: add missing put_device() call in at_dma_xlate()
dmaengine: at_hdmac: check return value of of_find_device_by_node() in at_dma_xlate()
dmaengine: of-dma: Fix of_dma_router_xlate's of_dma_xlate handling
dmaengine: idxd: reset states after device disable or reset
dmaengine: acpi: Put the CSRT table after using it
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SYSFW ABI 3.0 has changed the rchan_oes_offset value for am654 to support
SR2.
Since the kernel now needs SYSFW API 3.0 to work because the merged irqchip
update, we need to also update the am654 rchan_oes_offset.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20200831091019.25273-1-peter.ujfalusi@ti.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Export admin command status to sysfs attribute in order to allow user to
retrieve configuration error. Allows user tooling to retrieve the command
error and provide more user friendly error messages.
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/159865278770.29455.8026892329182750127.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Add sysfs attribute max_batch_size to wq in order to allow the max batch
size configured on a per wq basis. Add support code to configure
the valid user input on wq enable. This is a performance tuning
parameter.
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/159865273617.29141.4383066301730821749.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Add sysfs attribute max_xfer_size to wq in order to allow the max xfer
size configured on a per wq basis. Add support code to configure
the valid user input on wq enable. This is a performance tuning
parameter.
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/159865265404.29141.3049399618578194052.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Common pattern of handling deferred probe can be simplified with
dev_err_probe(). Less code and the error value gets printed.
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200828152637.16903-3-krzk@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Common pattern of handling deferred probe can be simplified with
dev_err_probe(). Less code and the error value gets printed.
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200828152637.16903-2-krzk@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Common pattern of handling deferred probe can be simplified with
dev_err_probe(). Less code and the error value gets printed.
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200828152637.16903-1-krzk@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Split IS_ERR_OR_NULL() check followed by additional conditional
to two simple conditionals. This increases readability and saves memory:
Function old new delta
dma_request_chan 700 697 -3
Total: Before=10224, After=10221, chg -0.03%
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200828144519.14483-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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New drivers should use dma_request_chan() instead
dma_request_slave_channel()
dma_request_slave_channel() is a simple wrapper for dma_request_chan()
eating up the error code for channel request failure and makes deferred
probing impossible.
Move the dma_request_slave_channel() into the header as inline function,
mark it as deprecated.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20200828110507.22407-1-peter.ujfalusi@ti.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Commit ef91bb196b0d ("kernel.h: Silence sparse warning in
lower_32_bits") caused new warnings to show in the fsldma driver, but
that commit was not to blame: it only exposed some very incorrect code
that tried to take the low 32 bits of an address.
That made no sense for multiple reasons, the most notable one being that
that code was intentionally limited to only 32-bit ppc builds, so "only
low 32 bits of an address" was completely nonsensical. There were no
high bits to mask off to begin with.
But even more importantly fropm a correctness standpoint, turning the
address into an integer then caused the subsequent address arithmetic to
be completely wrong too, and the "+1" actually incremented the address
by one, rather than by four.
Which again was incorrect, since the code was reading two 32-bit values
and trying to make a 64-bit end result of it all. Surprisingly, the
iowrite64() did not suffer from the same odd and incorrect model.
This code has never worked, but it's questionable whether anybody cared:
of the two users that actually read the 64-bit value (by way of some C
preprocessor hackery and eventually the 'get_cdar()' inline function),
one of them explicitly ignored the value, and the other one might just
happen to work despite the incorrect value being read.
This patch at least makes it not fail the build any more, and makes the
logic superficially sane. Whether it makes any difference to the code
_working_ or not shall remain a mystery.
Compile-tested-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Starting with core version 4.3.a the DMA bus attributes can (and should) be
read from the INTERFACE_DESCRIPTION (0x10) register.
For older core versions, this will still need to be provided from the
device-tree.
The bus-type values are identical to the ones stored in the device-trees,
so we just need to read them. Bus-width values are stored in log2 values,
so we just need to use them as shift values to make them equivalent to the
current format.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20200825151950.57605-7-alexandru.ardelean@analog.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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The channel parameters (which are read from the device-tree) are adjusted
for the DMAEngine framework in the axi_dmac_parse_chan_dt() function, after
they are read from the device-tree.
When we want to read these from registers, we will need to use the same
logic, so this change splits the logic into a separate function.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20200825151950.57605-6-alexandru.ardelean@analog.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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All these attributes will be read from registers in newer core versions, so
just wrap the logic into a function.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20200825151950.57605-5-alexandru.ardelean@analog.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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The clock may also be required to read registers from the IP core (if it is
provided and the driver needs to control it).
So, move it earlier in the probe.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20200825151950.57605-4-alexandru.ardelean@analog.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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We want to enable the clock right after it is obtained. Then later we'll
want to read the core version via register-access (which requires the clock
to be enabled).
The initialization of the active_descs list can be postponed after reading
from registers (or reading the device-tree).
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20200825151950.57605-3-alexandru.ardelean@analog.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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The 'version' of the IP core will be needed to adapt the driver to a new
feature (i.e. reading some DMA parameters from registers).
To do that, the version will be checked, so this is being moved out of the
axi_dmac_detect_caps() function.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20200825151950.57605-2-alexandru.ardelean@analog.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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In probe, IRQ is requested before zchan->id is initialized which can be
read in the irq handler. Hence, shift request irq after other initializations
complete.
Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
Reviewed-by: Paul Cercueil <paul@crapouillou.net>
Link: https://lore.kernel.org/r/20200821034423.12713-1-madhuparnabhowmik10@gmail.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Instruction dump uses two printk() in a row to print one instruction. Use
KERN_CONT to prevent breaking the output in the middle.
Signed-off-by: Łukasz Stelmach <l.stelmach@samsung.com>
Link: https://lore.kernel.org/r/20200813204123.19044-1-l.stelmach@samsung.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Fix typo in comments offset related to padding bytes.
Signed-off-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
Link: https://lore.kernel.org/r/d7c7e56a83a13a62438a6c1a23863015a3760581.1597327654.git.gustavo.pimentel@synopsys.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Fix the source and destination physical address calculation of a
peripheral device on scatter-gather implementation.
This issue manifested during tests using a 64 bits architecture system.
The abnormal behavior wasn't visible before due to all previous tests
were done using 32 bits architecture system, that masked his effect.
Fixes: e63d79d1ffcd ("dmaengine: Add Synopsys eDMA IP core driver")
Cc: stable@vger.kernel.org
Signed-off-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
Link: https://lore.kernel.org/r/8d3ab7e2ba96563fe3495b32f60077fffb85307d.1597327623.git.gustavo.pimentel@synopsys.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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The direction has been already validated in the main callback and there is
no need to check it again in the TR mode handlers for slave_sg and cyclic.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20200824120120.9270-1-peter.ujfalusi@ti.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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The TR which needs to be initialized for the next sg entry is indexed by
tr_idx and not by the running i counter.
In case any sub element in the SG needs more than one TR, the code would
corrupt an already configured TR.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20200824120108.9178-1-peter.ujfalusi@ti.com
Fixes: 6cf668a4ef829 ("dmaengine: ti: k3-udma: Use the TR counter helper for slave_sg and cyclic")
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Move the burst len fixup after setting the generic value for it. This
finally enables the fixup introduced by commit 137bd11090d8 ("dmaengine:
pl330: Align DMA memcpy operations to MFIFO width"), which otherwise was
overwritten by the generic value.
Reported-by: kernel test robot <lkp@intel.com>
Fixes: 137bd11090d8 ("dmaengine: pl330: Align DMA memcpy operations to MFIFO width")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20200825064617.16193-1-m.szyprowski@samsung.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.
[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
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If memory allocation for 'atslave' succeed, at_dma_xlate() doesn't have a
corresponding kfree() in exception handling. Thus add kfree() for this
function implementation.
Fixes: bbe89c8e3d59 ("at_hdmac: move to generic DMA binding")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20200817115728.1706719-4-yukuai3@huawei.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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If of_find_device_by_node() succeed, at_dma_xlate() doesn't have a
corresponding put_device(). Thus add put_device() to fix the exception
handling for this function implementation.
Fixes: bbe89c8e3d59 ("at_hdmac: move to generic DMA binding")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20200817115728.1706719-3-yukuai3@huawei.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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at_dma_xlate()
The reurn value of of_find_device_by_node() is not checked, thus null
pointer dereference will be triggered if of_find_device_by_node()
failed.
Fixes: bbe89c8e3d59 ("at_hdmac: move to generic DMA binding")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20200817115728.1706719-2-yukuai3@huawei.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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The sparse tool complains as follows:
drivers/dma/xilinx/xilinx_dpdma.c:349:37: warning:
symbol 'dpdma_debugfs_reqs' was not declared. Should it be static?
This variable is not used outside of xilinx_dpdma.c, so this commit
marks it static.
Fixes: 1d220435cab3 ("dmaengine: xilinx: dpdma: Add debugfs support")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Hyun Kwon <hyun.kwon@xilinx.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://lore.kernel.org/r/20200818112217.43816-1-weiyongjun1@huawei.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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DW DMA IP-core provides a way to synthesize the DMA controller with
channels having different parameters like maximum burst-length,
multi-block support, maximum data width, etc. Those parameters both
explicitly and implicitly affect the channels performance. Since DMA slave
devices might be very demanding to the DMA performance, let's provide a
functionality for the slaves to be assigned with DW DMA channels, which
performance according to the platform engineer fulfill their requirements.
After this patch is applied it can be done by passing the mask of suitable
DMA-channels either directly in the dw_dma_slave structure instance or as
a fifth cell of the DMA DT-property. If mask is zero or not provided, then
there is no limitation on the channels allocation.
For instance Baikal-T1 SoC is equipped with a DW DMAC engine, which first
two channels are synthesized with max burst length of 16, while the rest
of the channels have been created with max-burst-len=4. It would seem that
the first two channels must be faster than the others and should be more
preferable for the time-critical DMA slave devices. In practice it turned
out that the situation is quite the opposite. The channels with
max-burst-len=4 demonstrated a better performance than the channels with
max-burst-len=16 even when they both had been initialized with the same
settings. The performance drop of the first two DMA-channels made them
unsuitable for the DW APB SSI slave device. No matter what settings they
are configured with, full-duplex SPI transfers occasionally experience the
Rx FIFO overflow. It means that the DMA-engine doesn't keep up with
incoming data pace even though the SPI-bus is enabled with speed of 25MHz
while the DW DMA controller is clocked with 50MHz signal. There is no such
problem has been noticed for the channels synthesized with
max-burst-len=4.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20200731200826.9292-6-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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According to the DW DMA controller Databook 2.18b (page 40 "3.5 Memory
Peripherals") memory peripherals don't have handshaking interface
connected to the controller, therefore they can never be a flow
controller. Since the CTLx.SRC_MSIZE and CTLx.DEST_MSIZE are properties
valid only for peripherals with a handshaking interface, we can freely
zero these fields out if the memory peripheral is selected to be the
source or the destination of the DMA transfers.
Note according to the databook, length of burst transfers to memory is
always equal to the number of data items available in a channel FIFO or
data items required to complete the block transfer, whichever is smaller;
length of burst transfers from memory is always equal to the space
available in a channel FIFO or number of data items required to complete
the block transfer, whichever is smaller.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20200731200826.9292-5-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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Indeed in case of the DMA_DEV_TO_MEM DMA transfers it's enough to take the
destination memory address and the destination master data width into
account to calculate the CTLx.DST_TR_WIDTH setting of the memory
peripheral. According to the DW DMAC IP-core Databook 2.18b (page 66,
Example 5) at the and of a DMA transfer when the DMA-channel internal FIFO
is left with data less than for a single destination burst transaction,
the destination peripheral will enter the Single Transaction Region where
the DW DMA controller can complete a block transfer to the destination
using single transactions (non-burst transaction of CTLx.DST_TR_WIDTH
bytes). If there is no enough data in the DMA-channel internal FIFO for
even a single non-burst transaction of CTLx.DST_TR_WIDTH bytes, then the
channel enters "FIFO flush mode". That mode is activated to empty the FIFO
and flush the leftovers out to the memory peripheral. The flushing
procedure is simple. The data is sent to the memory by means of a set of
single transaction of CTLx.SRC_TR_WIDTH bytes. To sum up it's redundant to
use the LLPs length to find out the CTLx.DST_TR_WIDTH parameter value,
since each DMA transfer will be completed with the CTLx.SRC_TR_WIDTH bytes
transaction if it is required.
We suggest to remove the LLP entry length from the statement which
calculates the memory peripheral DMA transaction width since it's
redundant due to the feature described above. By doing so we'll improve
the memory bus utilization and speed up the DMA-channel performance for
DMA_DEV_TO_MEM DMA-transfers.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200731200826.9292-4-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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CFGx.FIFO_MODE field controls a DMA-controller "FIFO readiness" criterion.
In other words it determines when to start pushing data out of a DW
DMAC channel FIFO to a destination peripheral or from a source
peripheral to the DW DMAC channel FIFO. Currently FIFO-mode is set to one
for all DW DMAC channels. It means they are tuned to flush data out of
FIFO (to a memory peripheral or by accepting the burst transaction
requests) when FIFO is at least half-full (except at the end of the block
transfer, when FIFO-flush mode is activated) and are configured to get
data to the FIFO when it's at least half-empty.
Such configuration is a good choice when there is no slave device involved
in the DMA transfers. In that case the number of bursts per block is less
than when CFGx.FIFO_MODE = 0 and, hence, the bus utilization will improve.
But the latency of DMA transfers may increase when CFGx.FIFO_MODE = 1,
since DW DMAC will wait for the channel FIFO contents to be either
half-full or half-empty depending on having the destination or the source
transfers. Such latencies might be dangerous in case if the DMA transfers
are expected to be performed from/to a slave device. Since normally
peripheral devices keep data in internal FIFOs, any latency at some
critical moment may cause one being overflown and consequently losing
data. This especially concerns a case when either a peripheral device is
relatively fast or the DW DMAC engine is relatively slow with respect to
the incoming data pace.
In order to solve problems, which might be caused by the latencies
described above, let's enable the FIFO half-full/half-empty "FIFO
readiness" criterion only for DMA transfers with no slave device involved.
Thanks to the commit 99ba8b9b0d97 ("dmaengine: dw: Initialize channel
before each transfer") we can freely do that in the generic
dw_dma_initialize_chan() method.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200731200826.9292-3-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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