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Date: Thu, 30 Jul 2020 05:11:30 +0530 From: Faiz Abbas <faiz_abbas@...com> To: <linux-kernel@...r.kernel.org>, <linux-mmc@...r.kernel.org> CC: <ulf.hansson@...aro.org>, <adrian.hunter@...el.com>, <faiz_abbas@...com> Subject: [PATCH] mmc: sdhci_am654: Add workaround for card detect debounce timer 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@...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 + */ + ktime_t timeout = ktime_add_ms(ktime_get(), + MAX_POWER_ON_TIMEOUT); + do { + if (ktime_compare(ktime_get(), timeout) > 0) { + dev_warn(mmc_dev(host->mmc), + "Power on failed\n"); + + return; + } + + writeb(val, host->ioaddr + reg); + usleep_range(1000, 10000); + } while (!(readb(host->ioaddr + reg) & SDHCI_POWER_ON)); + } } static int sdhci_am654_execute_tuning(struct mmc_host *mmc, u32 opcode) -- 2.17.1
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