linux-kernel - Re: [PATCH 2/3] mmc: mmc: do not use CMD13 to get status after speed mode switch

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Date:	Fri, 15 Jul 2016 15:10:57 -0700
From:	Bjorn Andersson <bjorn.andersson@...aro.org>
To:	Chaotian Jing <chaotian.jing@...iatek.com>,
	Ulf Hansson <ulf.hansson@...aro.org>
Cc:	Matthias Brugger <matthias.bgg@...il.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
	Masahiro Yamada <yamada.masahiro@...ionext.com>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org, srv_heupstream@...iatek.com,
	Sascha Hauer <kernel@...gutronix.de>,
	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	Georgi Djakov <georgi.djakov@...aro.org>
Subject: Re: [PATCH 2/3] mmc: mmc: do not use CMD13 to get status after speed
 mode switch

On Thu, May 19, 2016 at 1:47 AM, Chaotian Jing
<chaotian.jing@...iatek.com> wrote:
> Per JEDEC spec, it is not recommended to use CMD13 to get card status
> after speed mode switch. below are two reason about this:
> 1. CMD13 cannot be guaranteed due to the asynchronous operation.
> Therefore it is not recommended to use CMD13 to check busy completion
> of the timing change indication.
> 2. After switch to HS200, CMD13 will get response of 0x800, and even the
> busy signal gets de-asserted, the response of CMD13 is aslo 0x800.
>
> Signed-off-by: Chaotian Jing <chaotian.jing@...iatek.com>
> ---
>  drivers/mmc/core/mmc.c | 112 ++++++++++++++++++++-----------------------------
>  1 file changed, 45 insertions(+), 67 deletions(-)
>
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
[..]
> @@ -1274,20 +1254,18 @@ static int mmc_select_hs200(struct mmc_card *card)
>                 err = __mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
>                                    EXT_CSD_HS_TIMING, val,
>                                    card->ext_csd.generic_cmd6_time,
> -                                  true, send_status, true);
> +                                  true, false, true);
>                 if (err)
>                         goto err;
>                 old_timing = host->ios.timing;
>                 mmc_set_timing(host, MMC_TIMING_MMC_HS200);
> -               if (!send_status) {
> -                       err = mmc_switch_status(card);
> -                       /*
> -                        * mmc_select_timing() assumes timing has not changed if
> -                        * it is a switch error.
> -                        */
> -                       if (err == -EBADMSG)
> -                               mmc_set_timing(host, old_timing);
> -               }
> +               err = mmc_switch_status(card);
> +               /*
> +                * mmc_select_timing() assumes timing has not changed if
> +                * it is a switch error.
> +                */
> +               if (err == -EBADMSG)
> +                       mmc_set_timing(host, old_timing);

Sorry for not spotting this earlier, but with the move of the call of
mmc_switch_status() to after mmc_set_timing() we get following error
with sdhci-msm:

mmc0: mmc_select_hs200 failed, error -110
mmc0: error -110 whilst initialising MMC card
mmc0: Reset 0x1 never completed.
sdhci: =========== REGISTER DUMP (mmc0)===========
sdhci: Sys addr: 0x00000000 | Version: 0x00002e02
sdhci: Blk size: 0x00004000 | Blk cnt: 0x00000000
sdhci: Argument: 0x00000000 | Trn mode: 0x00000000
sdhci: Present: 0x01f80000 | Host ctl: 0x00000000
sdhci: Power: 0x00000000 | Blk gap: 0x00000000
sdhci: Wake-up: 0x00000000 | Clock: 0x00000003
sdhci: Timeout: 0x00000000 | Int stat: 0x00000000
sdhci: Int enab: 0x00000000 | Sig enab: 0x00000000
sdhci: AC12 err: 0x00000000 | Slot int: 0x00000000
sdhci: Caps: 0x322dc8b2 | Caps_1: 0x00008007
sdhci: Cmd: 0x00000000 | Max curr: 0x00000000
sdhci: Host ctl2: 0x00000000
sdhci: ADMA Err: 0x00000000 | ADMA Ptr: 0x0000000000000000
sdhci: ===========================================

But I if I understand the commit correctly this is the intention of
the patch (not the error, but the move).

Regards,
Bjorn

>         }
>  err:
>         if (err)
> --
> 1.8.1.1.dirty
>