On Tue, 25 Aug 2020 at 19:00, Faiz Abbas <faiz_abbas@xxxxxx> wrote:
>
> 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>
Applied for next, thanks!
Kind regards
Uffe
> ---
>
> 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
>
