From: Faiz Abbas <faiz_abbas@ti.com> To: Adrian Hunter <adrian.hunter@intel.com>, <linux-kernel@vger.kernel.org>, <linux-mmc@vger.kernel.org> Cc: <ulf.hansson@linaro.org> Subject: Re: [PATCH] mmc: sdhci_am654: Add workaround for card detect debounce timer Date: Wed, 5 Aug 2020 18:46:28 +0530 [thread overview] Message-ID: <3f7e85c7-b0ba-e6a8-8d9f-091413614773@ti.com> (raw) In-Reply-To: <c5b166c9-f9ba-e01e-b759-57ac93d99832@intel.com>
WARNING: multiple messages have this Message-ID (diff)
From: Faiz Abbas <faiz_abbas@ti.com> To: Adrian Hunter <adrian.hunter@intel.com>, <linux-kernel@vger.kernel.org>, <linux-mmc@vger.kernel.org> Cc: <ulf.hansson@linaro.org> Subject: Re: [PATCH] mmc: sdhci_am654: Add workaround for card detect debounce timer Date: Wed, 5 Aug 2020 18:46:28 +0530 [thread overview] Message-ID: <3f7e85c7-b0ba-e6a8-8d9f-091413614773@ti.com> (raw) Message-ID: <20200805131628.ZKAgl4w06TMy5inqZV8clcsPVix20_07ZGYzHEZESFY@z> (raw) In-Reply-To: <c5b166c9-f9ba-e01e-b759-57ac93d99832@intel.com> Hi Adrian, On 05/08/20 3:16 pm, Adrian Hunter wrote: > On 5/08/20 11:22 am, Faiz Abbas wrote: >> Hi Adrian, >> >> On 05/08/20 1:44 pm, Adrian Hunter wrote: >>> On 30/07/20 2:41 am, Faiz Abbas wrote: >>>> There is a one time delay because of a card detect debounce timer in the >>>> controller IP. This timer runs as soon as power is applied to the module >>>> regardless of whether a card is present or not and any writes to >>>> SDHCI_POWER_ON will return 0 before it expires. This timeout has been >>>> measured to be about 1 second in am654x and j721e. >>>> >>>> Write-and-read-back in a loop on SDHCI_POWER_ON for a maximum of >>>> 1.5 seconds to make sure that the controller actually powers on. >>>> >>>> Signed-off-by: Faiz Abbas <faiz_abbas@ti.com> >>>> --- >>>> drivers/mmc/host/sdhci_am654.c | 21 +++++++++++++++++++++ >>>> 1 file changed, 21 insertions(+) >>>> >>>> diff --git a/drivers/mmc/host/sdhci_am654.c b/drivers/mmc/host/sdhci_am654.c >>>> index 1718b9e8af63..55cff9de2f3e 100644 >>>> --- a/drivers/mmc/host/sdhci_am654.c >>>> +++ b/drivers/mmc/host/sdhci_am654.c >>>> @@ -272,6 +272,7 @@ static void sdhci_j721e_4bit_set_clock(struct sdhci_host *host, >>>> sdhci_set_clock(host, clock); >>>> } >>>> >>>> +#define MAX_POWER_ON_TIMEOUT 1500 /* ms */ >>>> static void sdhci_am654_write_b(struct sdhci_host *host, u8 val, int reg) >>>> { >>>> unsigned char timing = host->mmc->ios.timing; >>>> @@ -291,6 +292,26 @@ static void sdhci_am654_write_b(struct sdhci_host *host, u8 val, int reg) >>>> } >>>> >>>> writeb(val, host->ioaddr + reg); >>>> + if (reg == SDHCI_POWER_CONTROL && (val & SDHCI_POWER_ON)) { >>>> + /* >>>> + * Power on will not happen until the card detect debounce >>>> + * timer expires. Wait at least 1.5 seconds for the power on >>>> + * bit to be set >>>> + */ >>> >>> Can you use readb_poll_timeout() here? >>> >> >> The loop is write -> readback -> check for set bit -> write again and so on until timeout >> so poll_timeout() calls will not work. > > I mentioned it because pedantically you need to check the condition > again after a timeout. Alternatively, the read_poll_timeout macro Ideally, the timeout will never happen because the internal timer always expires at 1 second. The actual time spent in the loop can be anything less than 1 second depending on when clocks were enabled > can be used with a function, something like below (not even compile > tested!) > > static u8 write_power_on(struct sdhci_host *host, u8 val, int reg) > { > writeb(val, host->ioaddr + reg); > usleep_range(1000, 10000); > return readb(host->ioaddr + reg); > } > > #define MAX_POWER_ON_TIMEOUT 1500000 /* us */ > static void sdhci_am654_write_b(struct sdhci_host *host, u8 val, int reg) > { > unsigned char timing = host->mmc->ios.timing; > u8 pwr; > > if (reg == SDHCI_HOST_CONTROL) { > switch (timing) { > /* > * According to the data manual, HISPD bit > * should not be set in these speed modes. > */ > case MMC_TIMING_SD_HS: > case MMC_TIMING_MMC_HS: > case MMC_TIMING_UHS_SDR12: > case MMC_TIMING_UHS_SDR25: > val &= ~SDHCI_CTRL_HISPD; > } > } > > writeb(val, host->ioaddr + reg); > > /* > * Power on will not happen until the card detect debounce > * timer expires. Wait at least 1.5 seconds for the power on > * bit to be set > */ > if (reg == SDHCI_POWER_CONTROL && (val & SDHCI_POWER_ON) && > read_poll_timeout(write_power_on, pwr, (pwr & SDHCI_POWER_ON), 0, > MAX_POWER_ON_TIMEOUT, false, host, val, reg)) > dev_warn(mmc_dev(host->mmc), "Power on failed\n"); > return; > } > } > } > Looks good. Let me add this in v2. Thanks, Faiz
next prev parent reply other threads:[~2020-08-05 20:16 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-07-29 23:41 [PATCH] mmc: sdhci_am654: Add workaround for card detect debounce timer Faiz Abbas 2020-08-05 8:14 ` Adrian Hunter 2020-08-05 8:22 ` Faiz Abbas 2020-08-05 9:46 ` Adrian Hunter 2020-08-05 13:16 ` Faiz Abbas [this message] 2020-08-05 13:16 ` Faiz Abbas
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