On Apr 25, 2011, at 11:36 PM, Nath, Arindam wrote:
> Hi Philip,
>
>
>> -----Original Message-----
>> From: Philip Rakity [mailto:[email protected]]
>> Sent: Saturday, April 23, 2011 1:56 AM
>> To: [email protected]
>> Cc: Nath, Arindam
>> Subject: [PATCH] sdhci-pxa: add platform specific code for UHS
>> signaling
>>
>>
>> Marvell controller requires 1.8V bit in UHS control register 2
>> be set when doing UHS. eMMC does not require 1.8V for DDR.
>> add platform code to handle this.
>>
>> Signed-off-by: Philip Rakity <[email protected]>
>> ---
>> drivers/mmc/host/sdhci-pxa.c | 38
>> ++++++++++++++++++++++++++++++++++++++
>> 1 files changed, 38 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/mmc/host/sdhci-pxa.c b/drivers/mmc/host/sdhci-
>> pxa.c
>> index 0e64d66..279d677 100644
>> --- a/drivers/mmc/host/sdhci-pxa.c
>> +++ b/drivers/mmc/host/sdhci-pxa.c
>> @@ -94,7 +94,42 @@ static void platform_reset_exit(struct sdhci_host
>> *host, u8 mask)
>> }
>> }
>>
>> +static int set_uhs_signaling(struct sdhci_host *host, unsigned int
>> uhs)
>> +{
>> + u16 ctrl_2;
>> +
>> + /*
>> + * Set V18_EN -- UHS modes do not work without this.
>> + * does not change signaling voltage
>> + */
>> + ctrl_2 = sdhci_readw(host, SDHCI_HOST_CONTROL2);
>> +
>> + /* Select Bus Speed Mode for host */
>> + ctrl_2 &= ~SDHCI_CTRL_UHS_MASK;
>> + if (uhs == MMC_TIMING_UHS_SDR12)
>> + ctrl_2 |= SDHCI_CTRL_UHS_SDR12;
>> + else if (uhs == MMC_TIMING_UHS_SDR25)
>> + ctrl_2 |= SDHCI_CTRL_UHS_SDR25;
>> + else if (uhs == MMC_TIMING_UHS_SDR50) {
>> + ctrl_2 |= SDHCI_CTRL_UHS_SDR50;
>> + ctrl_2 |= SDHCI_CTRL_VDD_180;
>> + }
>> + else if (uhs == MMC_TIMING_UHS_SDR104) {
>> + ctrl_2 |= SDHCI_CTRL_UHS_SDR104;
>> + ctrl_2 |= SDHCI_CTRL_VDD_180;
>> + }
>> + else if (uhs == MMC_TIMING_UHS_DDR50) {
>> + ctrl_2 |= SDHCI_CTRL_UHS_DDR50;
>> + ctrl_2 |= SDHCI_CTRL_VDD_180;
>> + }
>
> Since SDR12 and SDR25 are also UHS modes, don't we need to set 1.8V signaling
> for them as well?
>
will double check with hardware folks.
>> + sdhci_writew(host, ctrl_2, SDHCI_HOST_CONTROL2);
>
> I am not sure about your controller, but as per the spec, we need to reset
> SDCLK before enabling 1.8V, and then re-enable SDCLK. Also there is a delay
> of 5ms between these two. Is that a concern here?
>
The bit must be set -- no need for 5ms delay since it does not control any
power source. Internal.
>> + pr_debug("%s:%s uhs = %d, ctrl_2 = %04X\n",
>> + __func__, mmc_hostname(host->mmc), uhs, ctrl_2);
>> + return 0;
>> +}
>
> Since, we are just returning 0 from this function, why not use *void* return
> type instead?
>
> Thanks,
> Arindam
>
>
--
To unsubscribe from this list: send the line "unsubscribe linux-mmc" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
