Re: [PATCH] mmc: core: Fix init_card in 52Mhz

Chaotian Jing
2015-09-30T09:03:15Z

On Wed, 2015-09-30 at 11:24 +0300, Adrian Hunter wrote:
> On 30/09/15 06:28, Chaotian Jing wrote:
> > Suppose that we got a data crc error, and it triggers the mmc_reset.
> > mmc_reset will call mmc_send_status to see if HW reset was supported.
> > before issue CMD13, it will do retune, and if EMMC was in HS400 mode,
> > it will reduce frequency to 52Mhz firstly, that results in card init
> > was doing at 52Mhz, So need ensure frequency is lower than 400Khz when
> > re-init card.
>
> The call to mmc_send_status() was originally only done for mmc_test and
> doesn't belong in a real reset. However the test parameter was removed
> to simplify the code by:
>
> commit 83533ab28380f6957af39a7b322e639e42dbdaf1
> Author: Johan Rudholm <johan.rudholm@axis.com>
> Date: Mon Jan 12 15:38:04 2015 +0100
>
> mmc: core: always check status after reset
>
> Always check if the card is alive after a successful reset. This allows
> us to remove mmc_hw_reset_check(), leaving mmc_hw_reset() as the only
> card reset interface.
>
> Signed-off-by: Johan Rudholm <johanru@axis.com>
> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
>
> IMHO having a test to check whether hw reset actually did reset the card
> is useful, so I would suggest putting back mmc_hw_reset_check() and
> removing the check from the non-test path.
>
> An alternative is to recognize that we don't want retuning here, and it is
> unlikely to be needed in the mmc_test case. So if retuning is needed, just
> skip the call to mmc_send_status() i.e.
>
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index f2d0c2ae85b1..c3749ba42739 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -1938,7 +1938,7 @@ static int mmc_reset(struct mmc_host *host)
> host->ops->hw_reset(host);
>
> /* If the reset has happened, then a status command will fail */
> - if (!mmc_send_status(card, &status)) {
> + if (!host->need_retune && !mmc_send_status(card, &status)) {
> mmc_host_clk_release(host);
> return -ENOSYS;
> }
>
> Could then make mmc_test aware of that:
>

> This solution is better, please help to upstream it. Thx!
> diff --git a/drivers/mmc/card/mmc_test.c b/drivers/mmc/card/mmc_test.c
> index b78cf5d403a3..7b105b97be78 100644
> --- a/drivers/mmc/card/mmc_test.c
> +++ b/drivers/mmc/card/mmc_test.c
> @@ -2272,6 +2272,16 @@ static int mmc_test_hw_reset(struct mmc_test_card *test)
> if (!mmc_card_mmc(card) || !mmc_can_reset(card))
> return RESULT_UNSUP_CARD;
>
> + err = mmc_send_status(card, NULL);
> + if (err)
> + return err;
> +
> + if (host->need_retune) {
> + pr_info("%s: cannot test hw reset because retune needed\n",
> + mmc_hostname(test->card->host));
> + return RESULT_FAIL;
> + }
> +
> err = mmc_hw_reset(host);
> if (!err)
> return RESULT_OK;
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index f2d0c2ae85b1..c3749ba42739 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -1938,7 +1938,7 @@ static int mmc_reset(struct mmc_host *host)
> host->ops->hw_reset(host);
>
> /* If the reset has happened, then a status command will fail */
> - if (!mmc_send_status(card, &status)) {
> + if (!host->need_retune && !mmc_send_status(card, &status)) {
> mmc_host_clk_release(host);
> return -ENOSYS;
> }
>
>
>
>
> >
> > Signed-off-by: Chaotian Jing <chaotian.jing@mediatek.com>
> > ---
> > drivers/mmc/core/mmc.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> > index e726903..f2d0c2a 100644
> > --- a/drivers/mmc/core/mmc.c
> > +++ b/drivers/mmc/core/mmc.c
> > @@ -1945,6 +1945,7 @@ static int mmc_reset(struct mmc_host *host)
> >
> > /* Set initial state and call mmc_set_ios */
> > mmc_set_initial_state(host);
> > + mmc_set_clock(host, host->f_init);
> > mmc_host_clk_release(host);
> >
> > return mmc_init_card(host, card->ocr, card);
> >
>