On 5/08/20 11:22 am, Faiz Abbas wrote:
> Hi Adrian,
>
> On 05/08/20 1:44 pm, Adrian Hunter wrote:
>> On 30/07/20 2:41 am, Faiz Abbas 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>
>>> ---
>>> 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
>>> + */
>>
>> Can you use readb_poll_timeout() here?
>>
>
> The loop is write -> readback -> check for set bit -> write again and so on until timeout
> so poll_timeout() calls will not work.
I mentioned it because pedantically you need to check the condition
again after a timeout. Alternatively, the read_poll_timeout macro
can be used with a function, something like below (not even compile
tested!)
static u8 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;
if (reg == SDHCI_HOST_CONTROL) {
switch (timing) {
/*
* According to the data manual, HISPD bit
* should not be set in these speed modes.
*/
case MMC_TIMING_SD_HS:
case MMC_TIMING_MMC_HS:
case MMC_TIMING_UHS_SDR12:
case MMC_TIMING_UHS_SDR25:
val &= ~SDHCI_CTRL_HISPD;
}
}
writeb(val, host->ioaddr + reg);
/*
* 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
*/
if (reg == SDHCI_POWER_CONTROL && (val & SDHCI_POWER_ON) &&
read_poll_timeout(write_power_on, pwr, (pwr & SDHCI_POWER_ON), 0,
MAX_POWER_ON_TIMEOUT, false, host, val, reg))
dev_warn(mmc_dev(host->mmc), "Power on failed\n");
return;
}
}
}
