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| 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/mmc.c | |
| parent | b315376573778b195e640a163675fb9f5937ddca (diff) | |
| download | lwn-3d705d14fe4c72be83bae1610680e209ee226b9d.tar.gz lwn-3d705d14fe4c72be83bae1610680e209ee226b9d.zip | |
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/mmc.c')
| -rw-r--r-- | drivers/mmc/core/mmc.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c index 1eda8dd8c867..31c43165f8bc 100644 --- a/drivers/mmc/core/mmc.c +++ b/drivers/mmc/core/mmc.c @@ -162,6 +162,7 @@ static int mmc_decode_csd(struct mmc_card *card) csd->read_partial = UNSTUFF_BITS(resp, 79, 1); csd->write_misalign = UNSTUFF_BITS(resp, 78, 1); csd->read_misalign = UNSTUFF_BITS(resp, 77, 1); + csd->dsr_imp = UNSTUFF_BITS(resp, 76, 1); csd->r2w_factor = UNSTUFF_BITS(resp, 26, 3); csd->write_blkbits = UNSTUFF_BITS(resp, 22, 4); csd->write_partial = UNSTUFF_BITS(resp, 21, 1); @@ -1272,6 +1273,13 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr, } /* + * handling only for cards supporting DSR and hosts requesting + * DSR configuration + */ + if (card->csd.dsr_imp && host->dsr_req) + mmc_set_dsr(host); + + /* * Select card, as all following commands rely on that. */ if (!mmc_host_is_spi(host)) { |