On 17/11/22 17:23, Adrian Hunter wrote: > On 17/11/22 13:07, Ulf Hansson wrote: >> On Thu, 17 Nov 2022 at 10:49, Sarthak Garg <quic_sartgarg@xxxxxxxxxxx> wrote: >>> >>> As per spec we should wait for 1ms after providing the SD clock to the >>> card again as part of voltage switch sequence but there seems to be a >>> violation here. Clocks are getting gated before 1ms as part of >>> sdhci_set_ios function where we try to reset SD Clock Enable by >>> resetting SDHCI_CLOCK_CARD_EN bit in SDHCI_CLOCK_CONTROL register >>> leading to voltage switch failures for specific SD cards. >>> Below ftraces also confirms the above understanding : >>> >>> 9.511367: mmc_host_set_uhs_voltage: mmc1 called >>> 9.511369: mmc_set_ios: mmc1: clock 0Hz busmode 2 powermode 2 cs 0 >>> Vdd 18 width 1 timing 0 >>> 9.511370: sdhci_set_ios: mmc1 called >>> 9.511370: sdhci_set_ios: mmc1 setting clock ios->clock: 0 host->clock: >>> 400000 >>> 9.511372: sdhci_msm_set_clock: mmc1 clock: 0 >>> 9.511394: sdhci_set_ios: mmc1 gating clocks by writing >>> ~SDHCI_CLOCK_CARD_EN to SDHCI_CLOCK_CONTROL register >>> 9.511413: sdhci_msm_set_clock: mmc1 clock: 0 >>> 9.511423: mmc_set_signal_voltage: mmc1 called >>> 9.533816: mmc_set_ios: mmc1: clock 400000Hz busmode 2 powermode 2 cs 0 >>> Vdd 18 width 1 timing 0 >>> 9.533820: sdhci_set_ios: mmc1 called >>> 9.533822: sdhci_set_ios: mmc1 setting clock ios->clock: 400000 >>> host->clock: 0 >>> 9.533826: sdhci_msm_set_clock: mmc1 clock: 400000 >>> 9.533925: sdhci_enable_clk: mmc1 Enabling clocks by writing >>> SDHCI_CLOCK_CARD_EN to SDHCI_CLOCK_CONTROL register >>> 9.533950: sdhci_set_ios: mmc1 gating clocks by writing >>> ~SDHCI_CLOCK_CARD_EN to SDHCI_CLOCK_CONTROL register >>> 9.533973: sdhci_msm_set_clock: mmc1 clock: 400000 >>> 9.534043: sdhci_enable_clk: mmc1 Enabling clocks by writing >>> SDHCI_CLOCK_CARD_EN to SDHCI_CLOCK_CONTROL register >>> 9.534045: mmc_host_set_uhs_voltage: mmc1 Done >>> >>> Wait for 1ms after enabling the clock post voltage switch to make sure >>> clock is kept alive for alteast 1ms as per spec. >>> >>> Signed-off-by: Sarthak Garg <quic_sartgarg@xxxxxxxxxxx> >> >> I don't know the exact behaviour of sdhci around this, so I will defer >> to Adrian's input for that. > > sdhci_set_ios() seems to be mucking around with the clock way > more than necessary. I'll go over it and see what can be done. I have now sent some patches: https://lore.kernel.org/linux-mmc/20221124170649.63851-1-adrian.hunter@xxxxxxxxx/T/#t > >> >> However, let me point out that in mmc_set_uhs_voltage() we are trying >> to take the 1ms into account. More precisely, after >> mmc_host_set_uhs_voltage() has been called to switch the voltage to >> 1.8V and to re-enable the clock, mmc_set_uhs_voltage() does a >> "mmc_delay(1)" and then it calls the ->card_busy() ops to check that >> card doesn't signal busy by holding DAT0 low. >> >> I understand that the code in mmc_set_uhs_voltage(), expects the host >> to be rather dumb from the HW perspective, which may not always be the >> case. Although, I would rather avoid introducing new host flags, along >> what you propose in the $subject patch. If this can't be managed in >> sdhci, without some new help from the mmc core, I would rather suggest >> that we introduce a new host callback that can be used to replace the >> entire part in mmc_host_set_uhs_voltage() (or something along those >> lines). >> >> Kind regards >> Uffe >> >>> --- >>> drivers/mmc/core/core.c | 4 ++++ >>> drivers/mmc/host/sdhci.c | 3 +++ >>> include/linux/mmc/host.h | 1 + >>> 3 files changed, 8 insertions(+) >>> >>> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c >>> index a1efda85c6f2..d63e00aab6cb 100644 >>> --- a/drivers/mmc/core/core.c >>> +++ b/drivers/mmc/core/core.c >>> @@ -1181,6 +1181,8 @@ int mmc_host_set_uhs_voltage(struct mmc_host *host) >>> host->ios.clock = 0; >>> mmc_set_ios(host); >>> >>> + host->doing_signal_voltage_switch = true; >>> + >>> if (mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_180)) >>> return -EAGAIN; >>> >>> @@ -1189,6 +1191,8 @@ int mmc_host_set_uhs_voltage(struct mmc_host *host) >>> host->ios.clock = clock; >>> mmc_set_ios(host); >>> >>> + host->doing_signal_voltage_switch = false; >>> + >>> return 0; >>> } >>> >>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c >>> index fb6e9a81f198..ac7c254eef4b 100644 >>> --- a/drivers/mmc/host/sdhci.c >>> +++ b/drivers/mmc/host/sdhci.c >>> @@ -2312,6 +2312,9 @@ void sdhci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios) >>> host->ops->set_clock(host, ios->clock); >>> host->clock = ios->clock; >>> >>> + if (mmc->doing_signal_voltage_switch) >>> + usleep_range(1000, 1250); >>> + >>> if (host->quirks & SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK && >>> host->clock) { >>> host->timeout_clk = mmc->actual_clock ? >>> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h >>> index 8fdd3cf971a3..06c88cd7a8bf 100644 >>> --- a/include/linux/mmc/host.h >>> +++ b/include/linux/mmc/host.h >>> @@ -521,6 +521,7 @@ struct mmc_host { >>> bool hsq_enabled; >>> >>> u32 err_stats[MMC_ERR_MAX]; >>> + bool doing_signal_voltage_switch; >>> unsigned long private[] ____cacheline_aligned; >>> }; >>> >>> -- >>> 2.17.1 >>> >
