RE: [PATCH v2 06/12] mmc: sd: add support for uhs bus speed mode selection

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Hi Subhash,


> -----Original Message-----
> From: Subhash Jadavani [mailto:subhashj@xxxxxxxxxxxxxx]
> Sent: Wednesday, March 23, 2011 11:44 AM
> To: Nath, Arindam; cjb@xxxxxxxxxx
> Cc: zhangfei.gao@xxxxxxxxx; prakity@xxxxxxxxxxx; linux-
> mmc@xxxxxxxxxxxxxxx; Su, Henry; Lu, Aaron; anath.amd@xxxxxxxxx
> Subject: RE: [PATCH v2 06/12] mmc: sd: add support for uhs bus speed
> mode selection
>
>
>
> > -----Original Message-----
> > From: linux-mmc-owner@xxxxxxxxxxxxxxx [mailto:linux-mmc-
> > owner@xxxxxxxxxxxxxxx] On Behalf Of Nath, Arindam
> > Sent: Wednesday, March 23, 2011 11:35 AM
> > To: Subhash Jadavani; cjb@xxxxxxxxxx
> > Cc: zhangfei.gao@xxxxxxxxx; prakity@xxxxxxxxxxx; linux-
> > mmc@xxxxxxxxxxxxxxx; Su, Henry; Lu, Aaron; anath.amd@xxxxxxxxx
> > Subject: RE: [PATCH v2 06/12] mmc: sd: add support for uhs bus speed
> > mode selection
> >
> > Hi Subhash,
> >
> >
> > > -----Original Message-----
> > > From: Subhash Jadavani [mailto:subhashj@xxxxxxxxxxxxxx]
> > > Sent: Monday, March 21, 2011 12:13 PM
> > > To: Nath, Arindam; cjb@xxxxxxxxxx
> > > Cc: zhangfei.gao@xxxxxxxxx; prakity@xxxxxxxxxxx; linux-
> > > mmc@xxxxxxxxxxxxxxx; Su, Henry; Lu, Aaron; anath.amd@xxxxxxxxx
> > > Subject: RE: [PATCH v2 06/12] mmc: sd: add support for uhs bus
> speed
> > > mode selection
> > >
> > >
> > >
> > > > -----Original Message-----
> > > > From: Arindam Nath [mailto:anath.amd@xxxxxxxxx] On Behalf Of
> > Arindam
> > > > Nath
> > > > Sent: Friday, March 04, 2011 5:03 PM
> > > > To: cjb@xxxxxxxxxx
> > > > Cc: zhangfei.gao@xxxxxxxxx; prakity@xxxxxxxxxxx;
> > > > subhashj@xxxxxxxxxxxxxx; linux-mmc@xxxxxxxxxxxxxxx;
> > henry.su@xxxxxxx;
> > > > aaron.lu@xxxxxxx; anath.amd@xxxxxxxxx; Arindam Nath
> > > > Subject: [PATCH v2 06/12] mmc: sd: add support for uhs bus speed
> > mode
> > > > selection
> > > >
> > > > This patch adds support for setting UHS-I bus speed mode during
> > UHS-I
> > > > initialization procedure. Since both the host and card can
> support
> > > > more than one bus speed, we select the highest speed based on
> both
> > of
> > > > their capabilities. First we set the bus speed mode for the card
> > > using
> > > > CMD6 mode 1, and then we program the host controller to support
> the
> > > > required speed mode. We also set High Speed Enable in case one of
> > the
> > > > UHS-I modes is selected. Since MMC_TIMING_UHS_SDR25 is same as
> > > > MMC_TIMING_SD_HS, we don't need to set the SDHCI_CTRL_HISPD flag
> > for
> > > > UHS SDR25 again. We also take care to reset SD clock before
> setting
> > > > UHS mode in the Host Control2 register, and then re-enable it as
> > per
> > > > the Host Controller spec v3.00. We set the clock frequency for
> the
> > > > UHS-I mode selected.
> > > >
> > > > Signed-off-by: Arindam Nath <arindam.nath@xxxxxxx>
> > > > ---
> > > >  drivers/mmc/core/sd.c    |   91
> > > > ++++++++++++++++++++++++++++++++++++++++++++++
> > > >  drivers/mmc/host/sdhci.c |   32 +++++++++++++++-
> > > >  drivers/mmc/host/sdhci.h |    5 +++
> > > >  include/linux/mmc/card.h |   16 ++++++++
> > > >  include/linux/mmc/host.h |    4 ++
> > > >  5 files changed, 146 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
> > > > index f6a4fab..ec0d8e6 100644
> > > > --- a/drivers/mmc/core/sd.c
> > > > +++ b/drivers/mmc/core/sd.c
> > > > @@ -464,6 +464,92 @@ static int sd_select_driver_type(struct
> > mmc_card
> > > > *card, u8 *status)
> > > >         return 0;
> > > >  }
> > > >
> > > > +static int sd_set_bus_speed_mode(struct mmc_card *card, u8
> > *status)
> > > > +{
> > > > +       unsigned int bus_speed, timing;
> > > > +       int err;
> > > > +
> > > > +       /*
> > > > +        * If the host doesn't support any of the UHS-I modes,
> fallback
> > > > on
> > > > +        * default speed.
> > > > +        */
> > > > +       if (!(card->host->caps & (MMC_CAP_UHS_SDR12 |
> MMC_CAP_UHS_SDR25 |
> > > > +           MMC_CAP_UHS_SDR50 | MMC_CAP_UHS_SDR104 |
> MMC_CAP_UHS_DDR50)))
> > > > +               return 0;
> > > > +
> > > > +       if (card->host->caps & MMC_CAP_UHS_SDR104) {
> > > > +               if (card->sw_caps.uhs_bus_mode & SD_MODE_UHS_SDR104)
> {
> > > > +                       bus_speed = UHS_SDR104_BUS_SPEED;
> > > > +                       timing = MMC_TIMING_UHS_SDR104;
> > > > +                       card->sw_caps.uhs_max_dtr = UHS_SDR104_MAX_DTR;
> > > > +               } else if (card->sw_caps.uhs_bus_mode &
> SD_MODE_UHS_SDR50)
> > > > {
> > > > +                       bus_speed = UHS_SDR50_BUS_SPEED;
> > > > +                       timing = MMC_TIMING_UHS_SDR50;
> > > > +                       card->sw_caps.uhs_max_dtr = UHS_SDR50_MAX_DTR;
> > > > +               } else if (card->sw_caps.uhs_bus_mode &
> SD_MODE_UHS_DDR50)
> > > > {
> > > > +                       bus_speed = UHS_DDR50_BUS_SPEED;
> > > > +                       timing = MMC_TIMING_UHS_DDR50;
> > > > +                       card->sw_caps.uhs_max_dtr = UHS_DDR50_MAX_DTR;
> > > > +               } else if (card->sw_caps.uhs_bus_mode &
> SD_MODE_UHS_SDR25)
> > > > {
> > > > +                       bus_speed = UHS_SDR25_BUS_SPEED;
> > > > +                       timing = MMC_TIMING_UHS_SDR25;
> > > > +                       card->sw_caps.uhs_max_dtr = UHS_SDR25_MAX_DTR;
> > > > +               }
> > >
> > > I would not agree that if Host cap is set to MMC_CAP_UHS_SDR104
> > implies
> > > that
> > > DDR50 mode is supported by host. There may be a case where host
> > > controller
> > > only support SDR timing modes.
> > > Basically if host should advertise all the supported modes (SDR104,
> > > SDR50,
> > > SDR25, SDR12 & DDR) by caps and then we should choose the highest
> > > performance mode depending on both the card and host's highest
> > > performance
> > > mode.
> > >
> > > So this should be the check:
> > >
> > >   if ((card->host->caps & MMC_CAP_UHS_SDR104 &&
> > > (card->sw_caps.uhs_bus_mode & SD_MODE_UHS_SDR104)) {
> > >                   bus_speed = UHS_SDR104_BUS_SPEED;
> > >                   timing = MMC_TIMING_UHS_SDR104;
> > >                   card->sw_caps.uhs_max_dtr = UHS_SDR104_MAX_DTR;
> > >   } else if ((card->host->caps & MMC_CAP_UHS_DDR50 &&
> > > (card->sw_caps.uhs_bus_mode & SD_MODE_UHS_DDR50)) {
> > >                   bus_speed = UHS_DDR50_BUS_SPEED;
> > >                   timing = MMC_TIMING_UHS_DDR50;
> > >                   card->sw_caps.uhs_max_dtr = UHS_DDR50_MAX_DTR;
> > >   } else if ((card->host->caps & MMC_CAP_UHS_SDR50 &&
> > > (card->sw_caps.uhs_bus_mode & SD_MODE_UHS_SDR50)) {
> > >                   bus_speed = UHS_SDR50_BUS_SPEED;
> > >                   timing = MMC_TIMING_UHS_SDR50;
> > >                   card->sw_caps.uhs_max_dtr = UHS_SDR50_MAX_DTR;
> > >   } else if ((card->host->caps & MMC_CAP_UHS_SDR25 &&
> > > (card->sw_caps.uhs_bus_mode & SD_MODE_UHS_SDR25)) {
> > >                   bus_speed = UHS_SDR50_BUS_SPEED;
> > >                   timing = MMC_TIMING_UHS_SDR25;
> > >                   card->sw_caps.uhs_max_dtr = UHS_SDR25_MAX_DTR;
> > >   } else if ((card->host->caps & MMC_CAP_UHS_SDR12 &&
> > > (card->sw_caps.uhs_bus_mode & SD_MODE_UHS_SDR12)) {
> > >                   bus_speed = UHS_SDR12_BUS_SPEED;
> > >                   timing = MMC_TIMING_UHS_SDR12;
> > >                   card->sw_caps.uhs_max_dtr = UHS_SDR12_MAX_DTR;
> > >   }
> >
> > A host capable of operating at a higher bus speed mode should be able
> > to support cards with a lower bus speed mode. In case of your
> > conditions checks above, you are checking for the exact match for the
> > bus speed modes, otherwise you will fall back on using default bus
> > speed mode, thus performance loss.
>
> Why should we implicitly assume that host supporting SDR104 mode would
> also
> support DDR50 mode? Is there any spec. which says so? If not then we
> should
> rely on host capability to take the decision. DDR50 would require
> different
> timing implementation on the host side and host may choose not to
> implement
> DDR50 timing support then?
>
> I would agree that host supporting SDR104 mode should also be
> supporting
> SDR50/SDR25/SDR12 modes but it may not be true for DDR50 mode.

Please refer to footnote of table 3-5 of the Physical Layer spec v3.01. It says:

"The card supports a UHS-I mode shall support all lower UHS-I modes."

So if this is true for card, doesn't the same apply to host?

Thanks,
Arindam

>
> >
> > Thanks,
> > Arindam
> >
> > >
> > > Regards,
> > > Subhash
> > >
> > >
> > > > +       } else if (card->host->caps & MMC_CAP_UHS_SDR50) {
> > > > +               if ((card->sw_caps.uhs_bus_mode & SD_MODE_UHS_SDR104)
> ||
> > > > +                   (card->sw_caps.uhs_bus_mode & SD_MODE_UHS_SDR50))
> {
> > > > +                       bus_speed = UHS_SDR50_BUS_SPEED;
> > > > +                       timing = MMC_TIMING_UHS_SDR50;
> > > > +                       card->sw_caps.uhs_max_dtr = UHS_SDR50_MAX_DTR;
> > > > +               } else if (card->sw_caps.uhs_bus_mode &
> SD_MODE_UHS_DDR50)
> > > > {
> > > > +                       bus_speed = UHS_DDR50_BUS_SPEED;
> > > > +                       timing = MMC_TIMING_UHS_DDR50;
> > > > +                       card->sw_caps.uhs_max_dtr = UHS_DDR50_MAX_DTR;
> > > > +               } else if (card->sw_caps.uhs_bus_mode &
> SD_MODE_UHS_SDR25)
> > > > {
> > > > +                       bus_speed = UHS_SDR25_BUS_SPEED;
> > > > +                       timing = MMC_TIMING_UHS_SDR25;
> > > > +                       card->sw_caps.uhs_max_dtr = UHS_SDR25_MAX_DTR;
> > > > +               }
> > > > +       } else if (card->host->caps & MMC_CAP_UHS_DDR50) {
> > > > +               if ((card->sw_caps.uhs_bus_mode & SD_MODE_UHS_SDR104)
> ||
> > > > +                   (card->sw_caps.uhs_bus_mode & SD_MODE_UHS_SDR50)
> ||
> > > > +                   (card->sw_caps.uhs_bus_mode & SD_MODE_UHS_DDR50))
> {
> > > > +                       bus_speed = UHS_DDR50_BUS_SPEED;
> > > > +                       timing = MMC_TIMING_UHS_DDR50;
> > > > +                       card->sw_caps.uhs_max_dtr = UHS_DDR50_MAX_DTR;
> > > > +               } else if (card->sw_caps.uhs_bus_mode &
> SD_MODE_UHS_SDR25)
> > > > {
> > > > +                       bus_speed = UHS_SDR25_BUS_SPEED;
> > > > +                       timing = MMC_TIMING_UHS_SDR25;
> > > > +                       card->sw_caps.uhs_max_dtr = UHS_SDR25_MAX_DTR;
> > > > +               }
> > > > +       } else if (card->host->caps & MMC_CAP_UHS_SDR25) {
> > > > +               if ((card->sw_caps.uhs_bus_mode & SD_MODE_UHS_SDR104)
> ||
> > > > +                   (card->sw_caps.uhs_bus_mode & SD_MODE_UHS_SDR50)
> ||
> > > > +                   (card->sw_caps.uhs_bus_mode & SD_MODE_UHS_DDR50)
> ||
> > > > +                   (card->sw_caps.uhs_bus_mode & SD_MODE_UHS_SDR25))
> {
> > > > +                       bus_speed = UHS_SDR25_BUS_SPEED;
> > > > +                       timing = MMC_TIMING_UHS_SDR25;
> > > > +                       card->sw_caps.uhs_max_dtr = UHS_SDR25_MAX_DTR;
> > > > +               }
> > > > +       }
> > > > +
> > > > +       err = mmc_sd_switch(card, 1, 0, bus_speed, status);
> > > > +       if (err)
> > > > +               return err;
> > > > +
> > > > +       if ((status[16] & 0xF) != bus_speed)
> > > > +               printk(KERN_WARNING "%s: Problem setting bus speed
> > > > mode!\n",
> > > > +                       mmc_hostname(card->host));
> > > > +       else {
> > > > +               if (bus_speed) {
> > > > +                       mmc_set_timing(card->host, timing);
> > > > +                       mmc_set_clock(card->host,
> > > card->sw_caps.uhs_max_dtr);
> > > > +               }
> > > > +       }
> > > > +
> > > > +       return 0;
> > > > +}
> > > > +
> > > >  /*
> > > >   * UHS-I specific initialization procedure
> > > >   */
> > > > @@ -499,6 +585,11 @@ static int mmc_sd_init_uhs_card(struct
> > mmc_card
> > > > *card)
> > > >
> > > >         /* Set the driver strength for the card */
> > > >         err = sd_select_driver_type(card, status);
> > > > +       if (err)
> > > > +               goto out;
> > > > +
> > > > +       /* Set bus speed mode of the card */
> > > > +       err = sd_set_bus_speed_mode(card, status);
> > > >
> > > >  out:
> > > >         kfree(status);
> > > > diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> > > > index 5d3bb11..f127fa2 100644
> > > > --- a/drivers/mmc/host/sdhci.c
> > > > +++ b/drivers/mmc/host/sdhci.c
> > > > @@ -1278,7 +1278,13 @@ static void sdhci_set_ios(struct mmc_host
> > > *mmc,
> > > > struct mmc_ios *ios)
> > > >                 ctrl &= ~SDHCI_CTRL_HISPD;
> > > >
> > > >         if (host->version >= SDHCI_SPEC_300) {
> > > > -               u16 ctrl_2;
> > > > +               u16 clk, ctrl_2;
> > > > +
> > > > +               /* In case of UHS-I modes, set High Speed Enable */
> > > > +               if ((ios->timing == MMC_TIMING_UHS_SDR50) ||
> > > > +                   (ios->timing == MMC_TIMING_UHS_SDR104) ||
> > > > +                   (ios->timing == MMC_TIMING_UHS_DDR50))
> > > > +                       ctrl |= SDHCI_CTRL_HISPD;
> > > >
> > > >                 ctrl_2 = sdhci_readw(host, SDHCI_HOST_CONTROL2);
> > > >                 if (!(ctrl_2 & SDHCI_CTRL_PRESET_VAL_ENABLE)) {
> > > > @@ -1300,7 +1306,6 @@ static void sdhci_set_ios(struct mmc_host
> > *mmc,
> > > > struct mmc_ios *ios)
> > > >                          * need to reset SD Clock Enable before
> changing
> > > High
> > > >                          * Speed Enable to avoid generating clock
> gliches.
> > > >                          */
> > > > -                       u16 clk;
> > > >
> > > >                         /* Reset SD Clock Enable */
> > > >                         clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
> > > > @@ -1313,6 +1318,29 @@ static void sdhci_set_ios(struct mmc_host
> > > *mmc,
> > > > struct mmc_ios *ios)
> > > >                         clk |= SDHCI_CLOCK_CARD_EN;
> > > >                         sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
> > > >                 }
> > > > +
> > > > +               ctrl_2 = sdhci_readw(host, SDHCI_HOST_CONTROL2);
> > > > +
> > > > +               /* Select Bus Speed Mode for host */
> > > > +               if (ios->timing == MMC_TIMING_UHS_SDR25)
> > > > +                       ctrl_2 |= SDHCI_CTRL_UHS_SDR25;
> > > > +               else if (ios->timing == MMC_TIMING_UHS_SDR50)
> > > > +                       ctrl_2 |= SDHCI_CTRL_UHS_SDR50;
> > > > +               else if (ios->timing == MMC_TIMING_UHS_SDR104)
> > > > +                       ctrl_2 |= SDHCI_CTRL_UHS_SDR104;
> > > > +               else if (ios->timing == MMC_TIMING_UHS_DDR50)
> > > > +                       ctrl_2 |= SDHCI_CTRL_UHS_DDR50;
> > > > +
> > > > +               /* Reset SD Clock Enable */
> > > > +               clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
> > > > +               clk &= ~SDHCI_CLOCK_CARD_EN;
> > > > +               sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
> > > > +
> > > > +               sdhci_writew(host, ctrl_2, SDHCI_HOST_CONTROL2);
> > > > +
> > > > +               /* Re-enable SD Clock */
> > > > +               clk |= SDHCI_CLOCK_CARD_EN;
> > > > +               sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
> > > >         } else
> > > >                 sdhci_writeb(host, ctrl, SDHCI_HOST_CONTROL1);
> > > >
> > > > diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
> > > > index a407b5b..5bf244d 100644
> > > > --- a/drivers/mmc/host/sdhci.h
> > > > +++ b/drivers/mmc/host/sdhci.h
> > > > @@ -150,6 +150,11 @@
> > > >  #define SDHCI_ACMD12_ERR       0x3C
> > > >
> > > >  #define SDHCI_HOST_CONTROL2            0x3E
> > > > +#define  SDHCI_CTRL_UHS_SDR12          0x0000
> > > > +#define  SDHCI_CTRL_UHS_SDR25          0x0001
> > > > +#define  SDHCI_CTRL_UHS_SDR50          0x0002
> > > > +#define  SDHCI_CTRL_UHS_SDR104         0x0003
> > > > +#define  SDHCI_CTRL_UHS_DDR50          0x0004
> > > >  #define  SDHCI_CTRL_VDD_180            0x0008
> > > >  #define  SDHCI_CTRL_DRV_TYPE_B         0x0000
> > > >  #define  SDHCI_CTRL_DRV_TYPE_A         0x0010
> > > > diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
> > > > index 2d7f7a3..0b24c41 100644
> > > > --- a/include/linux/mmc/card.h
> > > > +++ b/include/linux/mmc/card.h
> > > > @@ -75,7 +75,23 @@ struct sd_ssr {
> > > >
> > > >  struct sd_switch_caps {
> > > >         unsigned int            hs_max_dtr;
> > > > +       unsigned int            uhs_max_dtr;
> > > > +#define UHS_SDR104_MAX_DTR     208000000
> > > > +#define UHS_SDR50_MAX_DTR      100000000
> > > > +#define UHS_DDR50_MAX_DTR      50000000
> > > > +#define UHS_SDR25_MAX_DTR      50000000
> > > >         unsigned int            uhs_bus_mode;
> > > > +#define UHS_SDR12_BUS_SPEED    0
> > > > +#define UHS_SDR25_BUS_SPEED    1
> > > > +#define UHS_SDR50_BUS_SPEED    2
> > > > +#define UHS_SDR104_BUS_SPEED   3
> > > > +#define UHS_DDR50_BUS_SPEED    4
> > > > +
> > > > +#define SD_MODE_UHS_SDR12      (1 << UHS_SDR12_BUS_SPEED)
> > > > +#define SD_MODE_UHS_SDR25      (1 << UHS_SDR25_BUS_SPEED)
> > > > +#define SD_MODE_UHS_SDR50      (1 << UHS_SDR50_BUS_SPEED)
> > > > +#define SD_MODE_UHS_SDR104     (1 << UHS_SDR104_BUS_SPEED)
> > > > +#define SD_MODE_UHS_DDR50      (1 << UHS_DDR50_BUS_SPEED)
> > > >         unsigned int            uhs_drv_type;
> > > >  #define SD_DRIVER_TYPE_B       0x01
> > > >  #define SD_DRIVER_TYPE_A       0x02
> > > > diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> > > > index bc2121e..4dfff6d 100644
> > > > --- a/include/linux/mmc/host.h
> > > > +++ b/include/linux/mmc/host.h
> > > > @@ -50,6 +50,10 @@ struct mmc_ios {
> > > >  #define MMC_TIMING_LEGACY      0
> > > >  #define MMC_TIMING_MMC_HS      1
> > > >  #define MMC_TIMING_SD_HS       2
> > > > +#define MMC_TIMING_UHS_SDR25   MMC_TIMING_SD_HS
> > > > +#define MMC_TIMING_UHS_SDR50   3
> > > > +#define MMC_TIMING_UHS_SDR104  4
> > > > +#define MMC_TIMING_UHS_DDR50   5
> > > >
> > > >         unsigned char   ddr;                    /* dual data rate used
> */
> > > >
> > > > --
> > > > 1.7.1
> > >
> > >
> >
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-mmc"
> in
> > the body of a message to majordomo@xxxxxxxxxxxxxxx
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
>


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