Hello Ulf, On Thu, Aug 14, 2014 at 11:26:28AM +0200, Ulf Hansson wrote: > 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. ok. > > *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); ok. > > 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. I think this doesn't work. What is your actual suggestion? if (card->csd.dsr_imp && host->dsr) ? The intended semantic is that if the device tree has: dsr = <$somevalue>; the DSR is written, and if there is no such property, DSR is unhandled. If you just check for host->dsr being != 0, how to differenciate between dsr = <0>; in the device tree and dsr not being specified? Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ | -- 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
