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>
---
v2: Use read_poll_timeout() standard macro
drivers/mmc/host/sdhci_am654.c | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
diff --git a/drivers/mmc/host/sdhci_am654.c b/drivers/mmc/host/sdhci_am654.c
index f9d24af12396..9a048c80dad4 100644
--- a/drivers/mmc/host/sdhci_am654.c
+++ b/drivers/mmc/host/sdhci_am654.c
@@ -6,6 +6,7 @@
*
*/
#include <linux/clk.h>
+#include <linux/iopoll.h>
#include <linux/of.h>
#include <linux/module.h>
#include <linux/pm_runtime.h>
@@ -272,9 +273,19 @@ static void sdhci_j721e_4bit_set_clock(struct sdhci_host *host,
sdhci_set_clock(host, clock);
}
+static u8 sdhci_am654_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;
+ int ret;
if (reg == SDHCI_HOST_CONTROL) {
switch (timing) {
@@ -291,6 +302,19 @@ 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
+ */
+ ret = read_poll_timeout(sdhci_am654_write_power_on, pwr,
+ pwr & SDHCI_POWER_ON, 0,
+ MAX_POWER_ON_TIMEOUT, false, host, val,
+ reg);
+ if (ret)
+ dev_warn(mmc_dev(host->mmc), "Power on failed\n");
+ }
}
static int sdhci_am654_execute_tuning(struct mmc_host *mmc, u32 opcode)
--
2.17.1
