RE: [PATCH v4 1/4]enable HW reset capbility

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> -----Original Message-----
> From: kyungmin78@xxxxxxxxx [mailto:kyungmin78@xxxxxxxxx] On Behalf Of
> Kyungmin Park
> Sent: Thursday, December 09, 2010 1:24 PM
> To: Dong, Chuanxiao
> Cc: linux-mmc@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; cjb@xxxxxxxxxx;
> arjan@xxxxxxxxxxxxxxx; alan@xxxxxxxxxxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx
> Subject: Re: [PATCH v4 1/4]enable HW reset capbility
> 
> On Wed, Dec 1, 2010 at 9:49 PM, Chuanxiao Dong <chuanxiao.dong@xxxxxxxxx>
> wrote:
> > From d3be0b4fe8e8a40294830dfd8d0543d1e957fd29 Mon Sep 17 00:00:00 2001
> > From: Chuanxiao Dong <chuanxiao.dong@xxxxxxxxx>
> > Date: Wed, 1 Dec 2010 19:14:02 +0800
> > Subject: [PATCH 1/4] enable HW reset caps of MMC card if card supports
> >
> > HW reset capbility enable bit is byte 162 in card EXT_CSD
> > register, only version4.4 card or later can support to enable
> > this feature.
> >
> > HW reset feature can be used to reset eMMC card when occures
> > timeout errors during read/write/erase.
> >
> > Signed-off-by: Chuanxiao Dong <chuanxiao.dong@xxxxxxxxx>
> > ---
> >  drivers/mmc/core/mmc.c   |   29 +++++++++++++++++++++++++++++
> >  include/linux/mmc/card.h |    1 +
> >  include/linux/mmc/mmc.h  |    1 +
> >  3 files changed, 31 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> > index 77f93c3..85cc7f6 100644
> > --- a/drivers/mmc/core/mmc.c
> > +++ b/drivers/mmc/core/mmc.c
> > @@ -310,6 +310,10 @@ static int mmc_read_ext_csd(struct mmc_card *card)
> >                        ext_csd[EXT_CSD_SEC_FEATURE_SUPPORT];
> >                card->ext_csd.trim_timeout = 300 *
> >                        ext_csd[EXT_CSD_TRIM_MULT];
> > +               /*
> > +                * check Hardware reset cap
> Check hardware.
> > +                */
> > +               card->ext_csd.rst = ext_csd[EXT_CSD_RST];
> >        }
> >
> >        if (ext_csd[EXT_CSD_ERASED_MEM_CONT])
> > @@ -484,6 +488,31 @@ static int mmc_init_card(struct mmc_host *host, u32
> ocr,
> >        }
> >
> >        /*
> > +        * eMMC4.4 version card has HW reset capbility.
> capability.
> > +        * Enable this feature here:
> > +        * RST_N_FUNCTION register is W/R, one time programmable
> Use RST_n_FUNCTION as spec.
> > +        * or readable.
> > +        * So need to enable this register only once after power on
> > +        */
> > +       if (card->csd.mmca_vsn >= CSD_SPEC_VER_4 &&
> > +                       card->ext_csd.rev >= 4 &&
> it should be card->ext_csd.rev >= 5 since 4 is obsolete.
> 
> Thank you,
> Kyungmin Park

Thanks, Park. I will fix this.
And by the way, I noticed mmc_read_ext_csd function also used card->ext_csd.rev >=4. Is there some other reason for this kind of using? Or it is just because at that time the value 4 has not be obsolete yet....?

Thanks.
Chuanxiao
> > +                       card->ext_csd.rst == 0) {
> > +               err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
> > +                               EXT_CSD_RST, 1);
> > +
> > +               if (err && err != -EBADMSG)
> > +                       goto free_card;
> > +
> > +               if (err) {
> > +                       printk(KERN_WARNING "%s: switch to rst enable
> "
> > +                                  "failed %d\n",
> > +                                  mmc_hostname(card->host), err);
> > +                       err = 0;
> > +               } else
> > +                       card->ext_csd.rst = 1;
> > +       }
> > +
> > +       /*
> >         * Activate high speed (if supported)
> >         */
> >        if ((card->ext_csd.hs_max_dtr != 0) &&
> > diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
> > index 8ce0827..ebee676 100644
> > --- a/include/linux/mmc/card.h
> > +++ b/include/linux/mmc/card.h
> > @@ -54,6 +54,7 @@ struct mmc_ext_csd {
> >        unsigned int            sec_trim_mult;  /* Secure trim
> multiplier  */
> >        unsigned int            sec_erase_mult; /* Secure erase multiplier
> */
> >        unsigned int            trim_timeout;           /* In
> milliseconds */
> > +       unsigned int            rst; /* hardware reset enable bit */
> >  };
> >
> >  struct sd_scr {
> > diff --git a/include/linux/mmc/mmc.h b/include/linux/mmc/mmc.h
> > index 956fbd8..b7ab0da 100644
> > --- a/include/linux/mmc/mmc.h
> > +++ b/include/linux/mmc/mmc.h
> > @@ -251,6 +251,7 @@ struct _mmc_csd {
> >  * EXT_CSD fields
> >  */
> >
> > +#define EXT_CSD_RST            162     /* onetime programmable R/W
> */
> >  #define EXT_CSD_ERASE_GROUP_DEF                175     /* R/W */
> >  #define EXT_CSD_ERASED_MEM_CONT                181     /* RO */
> >  #define EXT_CSD_BUS_WIDTH              183     /* R/W */
> > --
> > 1.6.6.1
> >
> > --
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