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@xxxxxx>
---
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
