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authorTomasz Moń <tomasz.mon@camlingroup.com>2022-01-17 10:19:54 +0100
committerVinod Koul <vkoul@kernel.org>2022-02-15 11:11:06 +0530
commit5b215c28b923539a04587b6a3f78a449f967ae32 (patch)
treefc8c6bc4bc185816f1577dd64468e758765e0335 /drivers/dma
parent4ae7094011bea9c1d5b2ea9d3d4d640b394e9630 (diff)
dmaengine: imx-sdma: restart cyclic channel if needed
Under heavy load resulting in high interrupt latencies, it is possible for imx UART requests to completely fill DMA buffer. When DMA channel is triggered and no SDMA owned buffer is available, SDMA stops. Thanks to the autoRTS feature, there is no data loss due to the SDMA stop if the UART is using hardware flow control. According to DMA Engine API Guide, DMA cyclic operation is performed until explicitly stopped. Restart the buffer after handling channel loop if the channel was stopped by SDMA. Signed-off-by: Tomasz Moń <tomasz.mon@camlingroup.com> Link: https://lore.kernel.org/r/20220117091955.1038937-1-tomasz.mon@camlingroup.com Signed-off-by: Vinod Koul <vkoul@kernel.org>
Diffstat (limited to 'drivers/dma')
-rw-r--r--drivers/dma/imx-sdma.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
index 75ec0754d4ad..330ff41cd614 100644
--- a/drivers/dma/imx-sdma.c
+++ b/drivers/dma/imx-sdma.c
@@ -701,6 +701,11 @@ static int sdma_config_ownership(struct sdma_channel *sdmac,
return 0;
}
+static int is_sdma_channel_enabled(struct sdma_engine *sdma, int channel)
+{
+ return !!(readl(sdma->regs + SDMA_H_STATSTOP) & BIT(channel));
+}
+
static void sdma_enable_channel(struct sdma_engine *sdma, int channel)
{
writel(BIT(channel), sdma->regs + SDMA_H_START);
@@ -860,6 +865,15 @@ static void sdma_update_channel_loop(struct sdma_channel *sdmac)
if (error)
sdmac->status = old_status;
}
+
+ /*
+ * SDMA stops cyclic channel when DMA request triggers a channel and no SDMA
+ * owned buffer is available (i.e. BD_DONE was set too late).
+ */
+ if (!is_sdma_channel_enabled(sdmac->sdma, sdmac->channel)) {
+ dev_warn(sdmac->sdma->dev, "restart cyclic channel %d\n", sdmac->channel);
+ sdma_enable_channel(sdmac->sdma, sdmac->channel);
+ }
}
static void mxc_sdma_handle_channel_normal(struct sdma_channel *data)