RE: [PATCH v2 03/12] mmc: sd: query function modes for uhs cards

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Hi Subhash,


> -----Original Message-----
> From: subhashj@xxxxxxxxxxxxxx [mailto:subhashj@xxxxxxxxxxxxxx]
> Sent: Wednesday, March 09, 2011 7:39 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 03/12] mmc: sd: query function modes for uhs
> cards
> 
> 
> 
> > -----Original Message-----
> > From: linux-mmc-owner@xxxxxxxxxxxxxxx [mailto:linux-mmc-
> > owner@xxxxxxxxxxxxxxx] 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 03/12] mmc: sd: query function modes for uhs cards
> >
> > SD cards which conform to Physical Layer Spec v3.01 can support
> > additional Bus Speed Modes, Driver Strength, and Current Limit
> > other than the default values. We use CMD6 mode 0 to read these
> > additional card functions. The values read here will be used
> > during UHS-I initialization steps.
> >
> > Signed-off-by: Arindam Nath <arindam.nath@xxxxxxx>
> > ---
> >  drivers/mmc/core/sd.c    |   99
> > +++++++++++++++++++++++++++++++++++++++-------
> >  include/linux/mmc/card.h |    3 +
> >  2 files changed, 87 insertions(+), 15 deletions(-)
> >
> > diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
> > index 3e82599..a63956b 100644
> > --- a/drivers/mmc/core/sd.c
> > +++ b/drivers/mmc/core/sd.c
> > @@ -283,25 +283,94 @@ static int mmc_read_switch(struct mmc_card
> *card)
> >  		return -ENOMEM;
> >  	}
> >
> > -	err = mmc_sd_switch(card, 0, 0, 1, status);
> > -	if (err) {
> > -		/* If the host or the card can't do the switch,
> > -		 * fail more gracefully. */
> > -		if ((err != -EINVAL)
> > -		 && (err != -ENOSYS)
> > -		 && (err != -EFAULT))
> > +	if (card->scr.sda_spec3) {
> > +		/* First find out the supported Bus Speed Modes. */
> > +		err = mmc_sd_switch(card, 0, 0, 1, status);
> Reading function-group-1 status applies for both SD3.0 and SD2.0 cards
> as
> well. With card->scr.sda_spec check, you are duplicating the same code
> in
> else part of it as well. You can optimize it to only one call to
> mmc_sd_switch() to read function-group-1.

Yes, there is a duplication of the code. I will try to minimize it in the next version.

> 
> > +		if (err) {
> > +			/*
> > +			 * If the host or the card can't do the switch,
> > +			 * fail more gracefully.
> > +			 */
> > +			if ((err != -EINVAL)
> > +			&& (err != -ENOSYS)
> > +			&& (err != -EFAULT))
> > +				goto out;
> > +
> > +			printk(KERN_WARNING "%s: problem reading "
> > +				"Bus Speed modes.\n",
> > +				mmc_hostname(card->host));
> > +			err = 0;
> > +
> >  			goto out;
> > +		}
> >
> > -		printk(KER	N_WARNING "%s: problem reading switch "
> > -			"capabilities, performance might suffer.\n",
> > -			mmc_hostname(card->host));
> > -		err = 0;
> > +		card->sw_caps.uhs_bus_mode = status[13];
> Is adding uhs* prefix is appropriate? If card supports SD3.0 spec means
> card
> have to support UHS modes? Can we have cards (SDXC?) which sets SD3.0
> spec
> bit in SCR but does not support any of the UHS modes. So in this case
> putting uhs* prefix might not be appropriate.

As per Physical Layer Spec v3.01, UHS-I can be applied to SDHC and SDXC cards. Cards which support UHS-I should have sda_spec3 set in the SCR register. Since we need to set the data rate depending on the exact UHS-I speed mode, I have prefixed the variable with uhs_ to make things clear.

Thanks,
Arindam

> 
> 
> > +
> > +		/* Find out Driver Strengths supported by the card */
> > +		err = mmc_sd_switch(card, 0, 2, 1, status);
> > +		if (err) {
> > +			/*
> > +			 * If the host or the card can't do the switch,
> > +			 * fail more gracefully.
> > +			 */
> > +			if ((err != -EINVAL)
> > +			&& (err != -ENOSYS)
> > +			&& (err != -EFAULT))
> > +				goto out;
> > +
> > +			printk(KERN_WARNING "%s: problem reading "
> > +				"Driver Strength.\n",
> > +				mmc_hostname(card->host));
> > +			err = 0;
> >
> > -		goto out;
> > -	}
> > +			goto out;
> > +		}
> >
> > -	if (status[13] & 0x02)
> > -		card->sw_caps.hs_max_dtr = 50000000;
> > +		card->sw_caps.uhs_drv_type = status[9];
> > +
> > +		/* Find out Current Limits supported by the card */
> > +		err = mmc_sd_switch(card, 0, 3, 1, status);
> > +		if (err) {
> > +			/*
> > +			 * If the host or the card can't do the switch,
> > +			 * fail more gracefully.
> > +			 */
> > +			if ((err != -EINVAL)
> > +			&& (err != -ENOSYS)
> > +			&& (err != -EFAULT))
> > +				goto out;
> > +
> > +			printk(KERN_WARNING "%s: problem reading "
> > +				"Current Limit.\n",
> > +				mmc_hostname(card->host));
> > +			err = 0;
> > +
> > +			goto out;
> > +		}
> > +
> > +		card->sw_caps.uhs_curr_limit = status[7];
> > +	} else {
> > +		err = mmc_sd_switch(card, 0, 0, 1, status);
> > +		if (err) {
> > +			/*
> > +			 * If the host or the card can't do the switch,
> > +			 * fail more gracefully.
> > +			 */
> > +			if ((err != -EINVAL)
> > +			&& (err != -ENOSYS)
> > +			&& (err != -EFAULT))
> > +				goto out;
> > +
> > +			printk(KERN_WARNING "%s: problem reading switch "
> > +				"capabilities, performance might suffer.\n",
> > +				mmc_hostname(card->host));
> > +			err = 0;
> > +			goto out;
> > +		}
> > +
> > +		if (status[13] & 0x02)
> > +			card->sw_caps.hs_max_dtr = 50000000;
> > +	}
> >
> >  out:
> >  	kfree(status);
> > diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
> > index 22b0335..7080f22 100644
> > --- a/include/linux/mmc/card.h
> > +++ b/include/linux/mmc/card.h
> > @@ -75,6 +75,9 @@ struct sd_ssr {
> >
> >  struct sd_switch_caps {
> >  	unsigned int		hs_max_dtr;
> > +	unsigned int		uhs_bus_mode;
> > +	unsigned int		uhs_drv_type;
> > +	unsigned int		uhs_curr_limit;
> >  };
> >
> >  struct sdio_cccr {
> > --
> > 1.7.1
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-mmc"
> in
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> 


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