diff options
| author | Sascha Hauer <s.hauer@pengutronix.de> | 2014-08-19 10:45:51 +0200 |
|---|---|---|
| committer | Ulf Hansson <ulf.hansson@linaro.org> | 2014-09-09 13:59:07 +0200 |
| commit | 3d705d14fe4c72be83bae1610680e209ee226b9d (patch) | |
| tree | f62e06a2feffe512962cf2ec00baccf52460cdbf /drivers/mmc/core/host.c | |
| parent | b315376573778b195e640a163675fb9f5937ddca (diff) | |
mmc: implement Driver Stage Register handling
Some eMMC and SD cards implement a DSR register that allows to tune
raise/fall times and drive strength of the CMD and DATA outputs.
The values to use depend on the card in use and the host.
It might be needed to reduce the drive strength to prevent voltage peaks
above the host's specification.
Implement a 'dsr' devicetree property that allows to specify the value
to set the DSR to. For non-dt setups the new members of mmc_host can be
set by board code.
This patch was initially authored by Sascha Hauer. It contains
improvements authored by Markus Niebel and Uwe Kleine-König.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Markus Niebel <Markus.Niebel@tq-group.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Diffstat (limited to 'drivers/mmc/core/host.c')
| -rw-r--r-- | drivers/mmc/core/host.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c index 95cceae96944..d572b2beb65a 100644 --- a/drivers/mmc/core/host.c +++ b/drivers/mmc/core/host.c @@ -452,6 +452,14 @@ int mmc_of_parse(struct mmc_host *host) if (of_find_property(np, "mmc-hs400-1_2v", &len)) host->caps2 |= MMC_CAP2_HS400_1_2V | MMC_CAP2_HS200_1_2V_SDR; + host->dsr_req = !of_property_read_u32(np, "dsr", &host->dsr); + if (host->dsr_req && (host->dsr & ~0xffff)) { + dev_err(host->parent, + "device tree specified broken value for DSR: 0x%x, ignoring\n", + host->dsr); + host->dsr_req = 0; + } + return 0; out: |