RE: [PATCH v1 1/1] mmc: sd: UHS-I bus speed should be set last in UHS initialization

["Subhash Jadavani" <subhashj@codeaurora.org>]

Hi Arindam,

> -----Original Message-----
> From: Nath, Arindam [mailto:Arindam.Nath@amd.com]
> Sent: Friday, August 05, 2011 10:54 PM
> To: Subhash Jadavani; linux-mmc@vger.kernel.org; 'Philip Rakity'
> Cc: linux-arm-msm@vger.kernel.org
> Subject: RE: [PATCH v1 1/1] mmc: sd: UHS-I bus speed should be set last
> in UHS initialization
> 
> Hi Subhash,
> 
> The patch in general looks good to me, I have one comment below.
> 
> > -----Original Message-----
> > From: Subhash Jadavani [mailto:subhashj@codeaurora.org]
> > Sent: Friday, August 05, 2011 9:55 PM
> > To: linux-mmc@vger.kernel.org; Nath, Arindam; 'Philip Rakity'
> > Cc: linux-arm-msm@vger.kernel.org
> > Subject: RE: [PATCH v1 1/1] mmc: sd: UHS-I bus speed should be set
> last
> > in UHS initialization
> >
> > Chris, Arindam, Philip,
> >
> > Please let me know you comments on this reworked patch.
> >
> > Regards,
> > Subhash
> >
> > > -----Original Message-----
> > > From: linux-arm-msm-owner@vger.kernel.org [mailto:linux-arm-msm-
> > > owner@vger.kernel.org] On Behalf Of Subhash Jadavani
> > > Sent: Thursday, August 04, 2011 4:08 PM
> > > To: linux-mmc@vger.kernel.org
> > > Cc: linux-arm-msm@vger.kernel.org; Subhash Jadavani
> > > Subject: [PATCH v1 1/1] mmc: sd: UHS-I bus speed should be set last
> > in
> > > UHS initialization
> > >
> > > mmc_sd_init_uhs_card function sets the driver type, current limit
> > > and bus speed mode on card as well as on host controller side.
> > >
> > > Currently bus speed mode is set by sending CMD6 to card and
> > > immediately setting the timing mode in host controller. But
> > > then before initiating tuning sequence, it also tries to set
> > > current limit by sending CMD6 to card which results in data
> > > timeout errors in controller if bus speed mode is SDR50/SDR104
> mode.
> > >
> > > So basically bus speed mode should be set only after current limit
> > > is set in the card and immediately after setting the bus speed
> mode,
> > > tuning sequence should be initiated.
> > >
> > > Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
> > > ---
> > >  drivers/mmc/core/sd.c |   65 ++++++++++++++++++++++++++++++++++---
> --
> > --
> > > --------
> > >  1 files changed, 45 insertions(+), 20 deletions(-)
> > >
> > > diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
> > > index ff27741..769e587 100644
> > > --- a/drivers/mmc/core/sd.c
> > > +++ b/drivers/mmc/core/sd.c
> > > @@ -459,10 +459,9 @@ 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)
> > > +static int sd_get_bus_speed_mode(struct mmc_card *card)
> > >  {
> > > -	unsigned int bus_speed = 0, timing = 0;
> > > -	int err;
> > > +	int bus_speed = 0;
> > >
> > >  	/*
> > >  	 * If the host doesn't support any of the UHS-I modes, fallback
> > > on
> > > @@ -475,32 +474,57 @@ static int sd_set_bus_speed_mode(struct
> > mmc_card
> > > *card, u8 *status)
> > >  	if ((card->host->caps & MMC_CAP_UHS_SDR104) &&
> > >  	    (card->sw_caps.sd3_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.sd3_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_SDR104 |
> > >  		    MMC_CAP_UHS_SDR50)) && (card->sw_caps.sd3_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_SDR104 |
> > >  		    MMC_CAP_UHS_SDR50 | MMC_CAP_UHS_SDR25)) &&
> > >  		   (card->sw_caps.sd3_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_SDR104 |
> > >  		    MMC_CAP_UHS_SDR50 | MMC_CAP_UHS_SDR25 |
> > >  		    MMC_CAP_UHS_SDR12)) && (card->sw_caps.sd3_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;
> > > +	}
> > > +
> > > +	return bus_speed;
> > > +}
> > > +
> > > +static int sd_set_bus_speed_mode(struct mmc_card *card, u8
> *status)
> > > +{
> > > +	int err, bus_speed;
> > > +	unsigned int timing = 0;
> > > +
> > > +	bus_speed = sd_get_bus_speed_mode(card);
> > > +
> > > +	switch (bus_speed) {
> > > +	case UHS_SDR104_BUS_SPEED:
> > > +		timing = MMC_TIMING_UHS_SDR104;
> > > +		card->sw_caps.uhs_max_dtr = UHS_SDR104_MAX_DTR;
> > > +		break;
> > > +	case UHS_DDR50_BUS_SPEED:
> > > +		timing = MMC_TIMING_UHS_DDR50;
> > > +		card->sw_caps.uhs_max_dtr = UHS_DDR50_MAX_DTR;
> > > +		break;
> > > +	case UHS_SDR50_BUS_SPEED:
> > > +		timing = MMC_TIMING_UHS_SDR50;
> > > +		card->sw_caps.uhs_max_dtr = UHS_SDR50_MAX_DTR;
> > > +		break;
> > > +	case UHS_SDR25_BUS_SPEED:
> > > +		timing = MMC_TIMING_UHS_SDR25;
> > > +		card->sw_caps.uhs_max_dtr = UHS_SDR25_MAX_DTR;
> > > +		break;
> > > +	case UHS_SDR12_BUS_SPEED:
> > > +		timing = MMC_TIMING_UHS_SDR12;
> > > +		card->sw_caps.uhs_max_dtr = UHS_SDR12_MAX_DTR;
> > > +		break;
> > > +	default:
> > > +		return 0;
> > >  	}
> > >
> > >  	card->sd_bus_speed = bus_speed;
> 
> There is redundancy in the use of a variable here. We have *bus_speed*,
> and we have *card->sd_bus_speed* which will eventually have the same
> value. The point to consider is this, if you use
> sd_get_bus_speed_mode() to return the current bus speed, then there is
> a function call overhead, may be minor, associated with the call. Right
> now we only use the return value from this function in
> sd_set_current_limit(), but in future there might be multiple calls
> from other functions. So rather than returning the *bus_speed* from
> sd_get_bus_speed() everytime, IMO it's better to have it stored in
> mmc_card structure, which can be used anytime later without any
> overhead. I would like to have another opinion on this.
> 

Yes, that is also fine. then I can do something like this: Rename
sd_get_bus_speed_mode to sd_update_bus_speed_mode() and this function will
just set the "card->sd_bus_speed" mode depending on card and host
capability. Then call sd_update_bus_speed_mode() in mmc_sd_init_uhs_card()
before calling
sd_select_driver_type(),sd_set_current_limit(),sd_set_bus_speed_mode()
functions and in all of these *set* functions, directly use
"card->sd_bus_speed".

Is this fine? if yes, then I can post the new patch with these changes.

Regards,
Subhash


> Thanks,
> Arindam
> 
> > > @@ -522,6 +546,7 @@ static int sd_set_bus_speed_mode(struct
> mmc_card
> > > *card, u8 *status)
> > >  static int sd_set_current_limit(struct mmc_card *card, u8 *status)
> > >  {
> > >  	int current_limit = 0;
> > > +	unsigned int bus_speed = sd_get_bus_speed_mode(card);
> > >  	int err;
> > >
> > >  	/*
> > > @@ -529,9 +554,9 @@ static int sd_set_current_limit(struct mmc_card
> > > *card, u8 *status)
> > >  	 * bus speed modes. For other bus speed modes, we set the default
> > >  	 * current limit of 200mA.
> > >  	 */
> > > -	if ((card->sd_bus_speed == UHS_SDR50_BUS_SPEED) ||
> > > -	    (card->sd_bus_speed == UHS_SDR104_BUS_SPEED) ||
> > > -	    (card->sd_bus_speed == UHS_DDR50_BUS_SPEED)) {
> > > +	if ((bus_speed == UHS_SDR50_BUS_SPEED) ||
> > > +	    (bus_speed == UHS_SDR104_BUS_SPEED) ||
> > > +	    (bus_speed == UHS_DDR50_BUS_SPEED)) {
> > >  		if (card->host->caps & MMC_CAP_MAX_CURRENT_800) {
> > >  			if (card->sw_caps.sd3_curr_limit &
> > > SD_MAX_CURRENT_800)
> > >  				current_limit = SD_SET_CURRENT_LIMIT_800;
> > > @@ -613,13 +638,13 @@ static int mmc_sd_init_uhs_card(struct
> mmc_card
> > > *card)
> > >  	if (err)
> > >  		goto out;
> > >
> > > -	/* Set bus speed mode of the card */
> > > -	err = sd_set_bus_speed_mode(card, status);
> > > +	/* Set current limit for the card */
> > > +	err = sd_set_current_limit(card, status);
> > >  	if (err)
> > >  		goto out;
> > >
> > > -	/* Set current limit for the card */
> > > -	err = sd_set_current_limit(card, status);
> > > +	/* Set bus speed mode of the card */
> > > +	err = sd_set_bus_speed_mode(card, status);
> > >  	if (err)
> > >  		goto out;
> > >
> > > --
> > > 1.7.1.1
> > >
> > > --
> > > Sent by a consultant of the Qualcomm Innovation Center, Inc.
> > > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
> > > Forum.
> > >
> > > --
> > > To unsubscribe from this list: send the line "unsubscribe linux-
> arm-
> > > msm" in
> > > the body of a message to majordomo@vger.kernel.org
> > > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >
>