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mmc: sdhci_am654: Add workaround for card detect debounce timer

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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>
Link: https://lore.kernel.org/r/20200825170015.32285-1-faiz_abbas@ti.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
This commit is contained in:
Faiz Abbas 2020-08-25 22:30:15 +05:30 committed by Ulf Hansson
parent d425e42d60
commit 7ca0f166f5
1 changed files with 24 additions and 0 deletions
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24
drivers/mmc/host/sdhci_am654.c
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@ -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)