On 13 August 2014 17:44, Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx> wrote: > From: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx> > > Some (e)MMC 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@xxxxxxxxxxxxxx> > Signed-off-by: Markus Niebel <Markus.Niebel@xxxxxxxxxxxx> > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx> > --- > Hello, > > earlier incarnations of this patch can be found at > > http://lists.infradead.org/pipermail/linux-arm-kernel/2014-July/272983.html > http://lists.infradead.org/pipermail/linux-arm-kernel/2014-May/259281.html > > I need this functionallity on a machine where the default driver strength of > the eMMC chip is too big for the SoC. It seems to work without adapting the > drive strength, but the vendor reports that the DSR should be set to a certain > value to prevent poor signal integrity and increased wearout. > > Best regards > Uwe > > Documentation/devicetree/bindings/mmc/mmc.txt | 2 ++ > drivers/mmc/core/host.c | 8 ++++++++ > drivers/mmc/core/mmc.c | 8 ++++++++ > drivers/mmc/core/mmc_ops.c | 21 +++++++++++++++++++++ > drivers/mmc/core/mmc_ops.h | 1 + > drivers/mmc/core/sd.c | 8 ++++++++ > include/linux/mmc/card.h | 3 ++- > include/linux/mmc/host.h | 3 +++ > 8 files changed, 53 insertions(+), 1 deletion(-) > > diff --git a/Documentation/devicetree/bindings/mmc/mmc.txt b/Documentation/devicetree/bindings/mmc/mmc.txt > index 3c18001dfd5d..05bac770b4d0 100644 > --- a/Documentation/devicetree/bindings/mmc/mmc.txt > +++ b/Documentation/devicetree/bindings/mmc/mmc.txt > @@ -40,6 +40,8 @@ Optional properties: > - mmc-hs200-1_2v: eMMC HS200 mode(1.2V I/O) is supported > - mmc-hs400-1_8v: eMMC HS400 mode(1.8V I/O) is supported > - mmc-hs400-1_2v: eMMC HS400 mode(1.2V I/O) is supported > +- dsr: Value the card's (optional) Driver Stage Register (DSR) should be > + programmed with. Let's clarify that this is a 16 bit value. > > *NOTE* on CD and WP polarity. To use common for all SD/MMC host controllers line > polarity properties, we have to fix the meaning of the "normal" and "inverted" > diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c > index 95cceae96944..52e83f389428 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; > > + if (of_find_property(np, "dsr", &len)) { > + u32 tmp; > + > + of_property_read_u32(np, "dsr", &tmp); > + host->dsr_req = 1; > + host->dsr = (u16)tmp; > + } > + Let's simplify the above with just: of_property_read_u16(np, "dsr", &host->dsr); > return 0; > > out: > diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c > index 793c6f7ddb04..fdc1ac1360c4 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); > @@ -1273,6 +1274,13 @@ 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) We don't need host->dsr_req. Instead just check host->dsr. > + mmc_set_dsr(host); > + > + /* > * Select card, as all following commands rely on that. > */ > if (!mmc_host_is_spi(host)) { > diff --git a/drivers/mmc/core/mmc_ops.c b/drivers/mmc/core/mmc_ops.c > index f51b5ba3bbea..37ed493d8030 100644 > --- a/drivers/mmc/core/mmc_ops.c > +++ b/drivers/mmc/core/mmc_ops.c > @@ -93,6 +93,27 @@ int mmc_deselect_cards(struct mmc_host *host) > return _mmc_select_card(host, NULL); > } > > +/* > + * Write the value specified in the device tree or board code into the optional > + * 16 bit Driver Stage Register. This can be used to tune raise/fall times and > + * drive strength of the DAT and CMD outputs. The actual meaning of a given > + * value is hardware dependant. > + * The presence of the DSR register can be determined from the CSD register, > + * bit 76. > + */ > +int mmc_set_dsr(struct mmc_host *host) > +{ > + int err; > + struct mmc_command cmd = {0}; > + > + cmd.opcode = MMC_SET_DSR; > + > + cmd.arg = ((u32)host->dsr << 16) | 0xffff; > + cmd.flags = MMC_RSP_NONE | MMC_CMD_AC; > + > + return mmc_wait_for_cmd(host, &cmd, MMC_CMD_RETRIES); > +} > + > int mmc_go_idle(struct mmc_host *host) > { > int err; > diff --git a/drivers/mmc/core/mmc_ops.h b/drivers/mmc/core/mmc_ops.h > index 80ae9f4e0293..390dac665b2a 100644 > --- a/drivers/mmc/core/mmc_ops.h > +++ b/drivers/mmc/core/mmc_ops.h > @@ -14,6 +14,7 @@ > > int mmc_select_card(struct mmc_card *card); > int mmc_deselect_cards(struct mmc_host *host); > +int mmc_set_dsr(struct mmc_host *host); > int mmc_go_idle(struct mmc_host *host); > int mmc_send_op_cond(struct mmc_host *host, u32 ocr, u32 *rocr); > int mmc_all_send_cid(struct mmc_host *host, u32 *cid); > diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c > index 0c44510bf717..25913889cbaa 100644 > --- a/drivers/mmc/core/sd.c > +++ b/drivers/mmc/core/sd.c > @@ -127,6 +127,7 @@ 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); > @@ -954,6 +955,13 @@ static int mmc_sd_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) Check host->dsr instead. > + mmc_set_dsr(host); > + > + /* > * Select card, as all following commands rely on that. > */ > if (!mmc_host_is_spi(host)) { > diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h > index d424b9de3aff..680a7f0188bb 100644 > --- a/include/linux/mmc/card.h > +++ b/include/linux/mmc/card.h > @@ -42,7 +42,8 @@ struct mmc_csd { > unsigned int read_partial:1, > read_misalign:1, > write_partial:1, > - write_misalign:1; > + write_misalign:1, > + dsr_imp:1; > }; > > struct mmc_ext_csd { > diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h > index 7960424d0bc0..9e9ad7b31bb9 100644 > --- a/include/linux/mmc/host.h > +++ b/include/linux/mmc/host.h > @@ -319,6 +319,7 @@ struct mmc_host { > #ifdef CONFIG_MMC_DEBUG > unsigned int removed:1; /* host is being removed */ > #endif > + unsigned int dsr_req:1; /* DSR is requested for Host */ Remove dsr_req. > > int rescan_disable; /* disable card detection */ > int rescan_entered; /* used with nonremovable devices */ > @@ -365,6 +366,8 @@ struct mmc_host { > > unsigned int slotno; /* used for sdio acpi binding */ > > + u16 dsr; /* optional driver stage (dsr) value */ > + > unsigned long private[0] ____cacheline_aligned; > }; > > -- > 2.0.1 > Kind regards Uffe -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
