Commit 7ca0f166 authored by Faiz Abbas's avatar Faiz Abbas Committed by Ulf Hansson
Browse files

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: default avatarFaiz Abbas <faiz_abbas@ti.com>
Link: https://lore.kernel.org/r/20200825170015.32285-1-faiz_abbas@ti.com


Signed-off-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
parent d425e42d

drivers/mmc/host/sdhci_am654.c

+24 −0
Original line number Diff line number Diff line
@@ -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)

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