* Re: [PATCH] mmc: sdhci-msm: Add retries when all tuning phases are found valid
2020-08-27 14:58 [PATCH] mmc: sdhci-msm: Add retries when all tuning phases are found valid Douglas Anderson
@ 2020-08-28 12:42 ` vbadigan
2020-08-31 14:14 ` Adrian Hunter
2020-09-02 9:03 ` Ulf Hansson
2 siblings, 0 replies; 4+ messages in thread
From: vbadigan @ 2020-08-28 12:42 UTC (permalink / raw)
To: Douglas Anderson
Cc: Ulf Hansson, Adrian Hunter, Andy Gross, Asutosh Das,
Bjorn Andersson, Chris Ball, Georgi Djakov,
Venkat Gopalakrishnan, linux-arm-msm, linux-kernel, linux-mmc
On 2020-08-27 20:28, Douglas Anderson wrote:
> As the comments in this patch say, if we tune and find all phases are
> valid it's _almost_ as bad as no phases being found valid. Probably
> all phases are not really reliable but we didn't detect where the
> unreliable place is. That means we'll essentially be guessing and
> hoping we get a good phase.
>
> This is not just a problem in theory. It was causing real problems on
> a real board. On that board, most often phase 10 is found as the only
> invalid phase, though sometimes 10 and 11 are invalid and sometimes
> just 11. Some percentage of the time, however, all phases are found
> to be valid. When this happens, the current logic will decide to use
> phase 11. Since phase 11 is sometimes found to be invalid, this is a
> bad choice. Sure enough, when phase 11 is picked we often get mmc
> errors later in boot.
>
> I have seen cases where all phases were found to be valid 3 times in a
> row, so increase the retry count to 10 just to be extra sure.
>
> Fixes: 415b5a75da43 ("mmc: sdhci-msm: Add platform_execute_tuning
> implementation")
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
>
Thanks for adding this logic.
Reviewed-by: Veerabhadrarao Badiganti <vbadigan@codeaurora.org>
> drivers/mmc/host/sdhci-msm.c | 18 +++++++++++++++++-
> 1 file changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/sdhci-msm.c
> b/drivers/mmc/host/sdhci-msm.c
> index b7e47107a31a..1b78106681e0 100644
> --- a/drivers/mmc/host/sdhci-msm.c
> +++ b/drivers/mmc/host/sdhci-msm.c
> @@ -1165,7 +1165,7 @@ static void sdhci_msm_set_cdr(struct sdhci_host
> *host, bool enable)
> static int sdhci_msm_execute_tuning(struct mmc_host *mmc, u32 opcode)
> {
> struct sdhci_host *host = mmc_priv(mmc);
> - int tuning_seq_cnt = 3;
> + int tuning_seq_cnt = 10;
> u8 phase, tuned_phases[16], tuned_phase_cnt = 0;
> int rc;
> struct mmc_ios ios = host->mmc->ios;
> @@ -1221,6 +1221,22 @@ static int sdhci_msm_execute_tuning(struct
> mmc_host *mmc, u32 opcode)
> } while (++phase < ARRAY_SIZE(tuned_phases));
>
> if (tuned_phase_cnt) {
> + if (tuned_phase_cnt == ARRAY_SIZE(tuned_phases)) {
> + /*
> + * All phases valid is _almost_ as bad as no phases
> + * valid. Probably all phases are not really reliable
> + * but we didn't detect where the unreliable place is.
> + * That means we'll essentially be guessing and hoping
> + * we get a good phase. Better to try a few times.
> + */
> + dev_dbg(mmc_dev(mmc), "%s: All phases valid; try again\n",
> + mmc_hostname(mmc));
> + if (--tuning_seq_cnt) {
> + tuned_phase_cnt = 0;
> + goto retry;
> + }
> + }
> +
> rc = msm_find_most_appropriate_phase(host, tuned_phases,
> tuned_phase_cnt);
> if (rc < 0)
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] mmc: sdhci-msm: Add retries when all tuning phases are found valid
2020-08-27 14:58 [PATCH] mmc: sdhci-msm: Add retries when all tuning phases are found valid Douglas Anderson
2020-08-28 12:42 ` vbadigan
@ 2020-08-31 14:14 ` Adrian Hunter
2020-09-02 9:03 ` Ulf Hansson
2 siblings, 0 replies; 4+ messages in thread
From: Adrian Hunter @ 2020-08-31 14:14 UTC (permalink / raw)
To: Douglas Anderson, Ulf Hansson
Cc: vbadigan, Andy Gross, Asutosh Das, Bjorn Andersson, Chris Ball,
Georgi Djakov, Venkat Gopalakrishnan, linux-arm-msm,
linux-kernel, linux-mmc
On 27/08/20 5:58 pm, Douglas Anderson wrote:
> As the comments in this patch say, if we tune and find all phases are
> valid it's _almost_ as bad as no phases being found valid. Probably
> all phases are not really reliable but we didn't detect where the
> unreliable place is. That means we'll essentially be guessing and
> hoping we get a good phase.
>
> This is not just a problem in theory. It was causing real problems on
> a real board. On that board, most often phase 10 is found as the only
> invalid phase, though sometimes 10 and 11 are invalid and sometimes
> just 11. Some percentage of the time, however, all phases are found
> to be valid. When this happens, the current logic will decide to use
> phase 11. Since phase 11 is sometimes found to be invalid, this is a
> bad choice. Sure enough, when phase 11 is picked we often get mmc
> errors later in boot.
>
> I have seen cases where all phases were found to be valid 3 times in a
> row, so increase the retry count to 10 just to be extra sure.
>
> Fixes: 415b5a75da43 ("mmc: sdhci-msm: Add platform_execute_tuning implementation")
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
> ---
>
> drivers/mmc/host/sdhci-msm.c | 18 +++++++++++++++++-
> 1 file changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> index b7e47107a31a..1b78106681e0 100644
> --- a/drivers/mmc/host/sdhci-msm.c
> +++ b/drivers/mmc/host/sdhci-msm.c
> @@ -1165,7 +1165,7 @@ static void sdhci_msm_set_cdr(struct sdhci_host *host, bool enable)
> static int sdhci_msm_execute_tuning(struct mmc_host *mmc, u32 opcode)
> {
> struct sdhci_host *host = mmc_priv(mmc);
> - int tuning_seq_cnt = 3;
> + int tuning_seq_cnt = 10;
> u8 phase, tuned_phases[16], tuned_phase_cnt = 0;
> int rc;
> struct mmc_ios ios = host->mmc->ios;
> @@ -1221,6 +1221,22 @@ static int sdhci_msm_execute_tuning(struct mmc_host *mmc, u32 opcode)
> } while (++phase < ARRAY_SIZE(tuned_phases));
>
> if (tuned_phase_cnt) {
> + if (tuned_phase_cnt == ARRAY_SIZE(tuned_phases)) {
> + /*
> + * All phases valid is _almost_ as bad as no phases
> + * valid. Probably all phases are not really reliable
> + * but we didn't detect where the unreliable place is.
> + * That means we'll essentially be guessing and hoping
> + * we get a good phase. Better to try a few times.
> + */
> + dev_dbg(mmc_dev(mmc), "%s: All phases valid; try again\n",
> + mmc_hostname(mmc));
> + if (--tuning_seq_cnt) {
> + tuned_phase_cnt = 0;
> + goto retry;
> + }
> + }
> +
> rc = msm_find_most_appropriate_phase(host, tuned_phases,
> tuned_phase_cnt);
> if (rc < 0)
>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] mmc: sdhci-msm: Add retries when all tuning phases are found valid
2020-08-27 14:58 [PATCH] mmc: sdhci-msm: Add retries when all tuning phases are found valid Douglas Anderson
2020-08-28 12:42 ` vbadigan
2020-08-31 14:14 ` Adrian Hunter
@ 2020-09-02 9:03 ` Ulf Hansson
2 siblings, 0 replies; 4+ messages in thread
From: Ulf Hansson @ 2020-09-02 9:03 UTC (permalink / raw)
To: Douglas Anderson
Cc: Veerabhadrarao Badiganti, Adrian Hunter, Andy Gross, Asutosh Das,
Bjorn Andersson, Chris Ball, Georgi Djakov,
Venkat Gopalakrishnan, linux-arm-msm, Linux Kernel Mailing List,
linux-mmc
On Thu, 27 Aug 2020 at 16:59, Douglas Anderson <dianders@chromium.org> wrote:
>
> As the comments in this patch say, if we tune and find all phases are
> valid it's _almost_ as bad as no phases being found valid. Probably
> all phases are not really reliable but we didn't detect where the
> unreliable place is. That means we'll essentially be guessing and
> hoping we get a good phase.
>
> This is not just a problem in theory. It was causing real problems on
> a real board. On that board, most often phase 10 is found as the only
> invalid phase, though sometimes 10 and 11 are invalid and sometimes
> just 11. Some percentage of the time, however, all phases are found
> to be valid. When this happens, the current logic will decide to use
> phase 11. Since phase 11 is sometimes found to be invalid, this is a
> bad choice. Sure enough, when phase 11 is picked we often get mmc
> errors later in boot.
>
> I have seen cases where all phases were found to be valid 3 times in a
> row, so increase the retry count to 10 just to be extra sure.
>
> Fixes: 415b5a75da43 ("mmc: sdhci-msm: Add platform_execute_tuning implementation")
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
Applied for fixes and by adding a stable tag, thanks!
Kind regards
Uffe
> ---
>
> drivers/mmc/host/sdhci-msm.c | 18 +++++++++++++++++-
> 1 file changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> index b7e47107a31a..1b78106681e0 100644
> --- a/drivers/mmc/host/sdhci-msm.c
> +++ b/drivers/mmc/host/sdhci-msm.c
> @@ -1165,7 +1165,7 @@ static void sdhci_msm_set_cdr(struct sdhci_host *host, bool enable)
> static int sdhci_msm_execute_tuning(struct mmc_host *mmc, u32 opcode)
> {
> struct sdhci_host *host = mmc_priv(mmc);
> - int tuning_seq_cnt = 3;
> + int tuning_seq_cnt = 10;
> u8 phase, tuned_phases[16], tuned_phase_cnt = 0;
> int rc;
> struct mmc_ios ios = host->mmc->ios;
> @@ -1221,6 +1221,22 @@ static int sdhci_msm_execute_tuning(struct mmc_host *mmc, u32 opcode)
> } while (++phase < ARRAY_SIZE(tuned_phases));
>
> if (tuned_phase_cnt) {
> + if (tuned_phase_cnt == ARRAY_SIZE(tuned_phases)) {
> + /*
> + * All phases valid is _almost_ as bad as no phases
> + * valid. Probably all phases are not really reliable
> + * but we didn't detect where the unreliable place is.
> + * That means we'll essentially be guessing and hoping
> + * we get a good phase. Better to try a few times.
> + */
> + dev_dbg(mmc_dev(mmc), "%s: All phases valid; try again\n",
> + mmc_hostname(mmc));
> + if (--tuning_seq_cnt) {
> + tuned_phase_cnt = 0;
> + goto retry;
> + }
> + }
> +
> rc = msm_find_most_appropriate_phase(host, tuned_phases,
> tuned_phase_cnt);
> if (rc < 0)
> --
> 2.28.0.297.g1956fa8f8d-goog
>
^ permalink raw reply [flat|nested] 4+ messages in thread