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

Adrian Hunter
2015-09-30T08:27:11Z

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:

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);
>