From: Douglas Anderson dianders@chromium.org
[ Upstream commit 9d5dcefb7b114d610aeb2371f6a6f119af316e43 ]
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 Reviewed-by: Veerabhadrarao Badiganti vbadigan@codeaurora.org Acked-by: Adrian Hunter adrian.hunter@intel.com Link: https://lore.kernel.org/r/20200827075809.1.If179abf5ecb67c963494db79c3bc4247... Signed-off-by: Ulf Hansson ulf.hansson@linaro.org Signed-off-by: Sasha Levin sashal@kernel.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 643fd1a1b88be..4970cd40813b2 100644 --- a/drivers/mmc/host/sdhci-msm.c +++ b/drivers/mmc/host/sdhci-msm.c @@ -1060,7 +1060,7 @@ 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; @@ -1124,6 +1124,22 @@ retry: } 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)