On 27 September 2012 00:04, Kevin Liu <[email protected]> wrote:
> 2012/9/26 Girish K S <[email protected]>:
>> On 26 September 2012 20:38, Kevin Liu <[email protected]> wrote:
>>> From: Kevin Liu <[email protected]>
>>>
>>> Host controller must enable 1.8v signal for UHS modes.
>>> Otherwise UHS modes won't take effect.
>>> But mmc core does NOT switch to 1.8v for DDR50 mode.
>>> So enable the 1.8v signal for mmc DDR50 mode in host
>>> driver.
>>>
>>> Signed-off-by: Kevin Liu <[email protected]>
>>> ---
>>> drivers/mmc/host/sdhci.c | 9 ++++++++-
>>> 1 files changed, 8 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>>> index 50e7a54..e3de041 100644
>>> --- a/drivers/mmc/host/sdhci.c
>>> +++ b/drivers/mmc/host/sdhci.c
>>> @@ -1529,8 +1529,15 @@ static void sdhci_do_set_ios(struct sdhci_host
>>> *host, struct mmc_ios *ios)
>>> ctrl_2 |= SDHCI_CTRL_UHS_SDR50;
>>> else if (ios->timing == MMC_TIMING_UHS_SDR104)
>>> ctrl_2 |= SDHCI_CTRL_UHS_SDR104;
>>> - else if (ios->timing == MMC_TIMING_UHS_DDR50)
>>> + else if (ios->timing == MMC_TIMING_UHS_DDR50) {
>>> + struct mmc_card *card;
>>> +
>>> ctrl_2 |= SDHCI_CTRL_UHS_DDR50;
>>> + card = container_of(&(host->mmc),
>>> + struct mmc_card, host);
>>> + if (mmc_card_mmc(card))
>>> + ctrl_2 |= SDHCI_CTRL_VDD_180;
>>> + }
>> If you want to set the voltage to 1.8. It has to be done from the core
>> layer using the api mmc_set_signal_voltage during the mmc card init.
>> as it is done for 1.2 volts switch. In the comment (mmc_card_init
>> function) it is explicitly mentioned
>> * 1.8V vccq at 3.3V core voltage (vcc) is not required
>> * in the JEDEC spec for DDR.
>> can you please check it. Still if you feel its necessary to change the
>> voltage to 1.8 v, you can do it from mmc_init_card function
>
> In JEDEC spec, there are two emmc device types which support DDR50.
> One type can work under signal 1.2v while the other type work under
> signal 1.8v or 3v. So current code just keep 3v for the second device
> type.
>
> But in SD host spec, 1.8v signal must be enabled for all UHS modes
> taking effect.
> So the fact is, if we use SD host to work with emmc chip, we have to
> select 1.8v in order to enable DDR50. Current code missed this.
>
> Because DDR50 shall can work under both signal 1.8v and 3v according
> to JEDEC spec, So I don't want to switch to 1.8v in mmc core code.
> It's the host controller requirement that 1.8v signal must be enabled
> in order to enable DDR50, which conflict with emmc spec. So I added
> this in host driver.
I understand. Thanks
>
> Thanks
> Kevin
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