RE: [PATCH 2/2] mmc: core: fix the signaling 1.8V for HS200

[Seungwon Jeon <tgih.jun@samsung.com>]

Subhash Jadavani <subhashj@codeaurora.org> wrote:
> Hi Seungwon,
> 
> On 4/23/2012 2:41 PM, Seungwon Jeon wrote:
> > Currently only 1.2V is treated for HS200 mode. If the host has
> > only 1.8V I/O capability not 1.2V, mmc_set_signal_voltage can't
> > be called for 1.8V HS200. EXT_CSD_CARD_TYPE_SDR_1_8V needs to be
> > considered.
> Commit text looks confusing to me. In this change, you are trying to set
> the 1.8V I/O voltage only if there is an error setting the 1.2v I/O? Can
> you please clarify more?
This patch's purpose is to support 1.8V I/O. Origin considers only 1.2V I/O case.
If the host has only 1.8V capability and card type is HS200 1.8V, there is no way to 1.8V I/O.

Assuming that card is type of HS200 1.2V and host has 1.2V capability,
the 1.2 I/O voltage will be tried. If it succeeds in 1.2V I/O ,
we don't need to trying the 1.8V I/O voltage though 1.8V I/O is possible.
But the 1.8V I/O may be tried in case of 1.2V I/O failure, so error condition is needed.

And error is initialized by -EINVAL at the first time.
Thus, if card and host only are capable of 1.8V I/O, we can try to set the 1.8V I/O
regardless of 1.2V I/O result.

Best regards,
Seungwon Jeon.

> >
> > Signed-off-by: Seungwon Jeon<tgih.jun@samsung.com>
> > ---
> >   drivers/mmc/core/mmc.c |   12 +++++++-----
> >   1 files changed, 7 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> > index ebb9522..71eb320 100644
> > --- a/drivers/mmc/core/mmc.c
> > +++ b/drivers/mmc/core/mmc.c
> > @@ -732,7 +732,7 @@ static int mmc_select_powerclass(struct mmc_card *card,
> >    */
> >   static int mmc_select_hs200(struct mmc_card *card)
> >   {
> > -	int idx, err = 0;
> > +	int idx, err = -EINVAL;
> >   	struct mmc_host *host;
> >   	static unsigned ext_csd_bits[] = {
> >   		EXT_CSD_BUS_WIDTH_4,
> > @@ -748,10 +748,12 @@ static int mmc_select_hs200(struct mmc_card *card)
> >   	host = card->host;
> >
> >   	if (card->ext_csd.card_type&  EXT_CSD_CARD_TYPE_SDR_1_2V&&
> > -	    host->caps2&  MMC_CAP2_HS200_1_2V_SDR)
> > -		if (mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_120, 0))
> > -			err = mmc_set_signal_voltage(host,
> > -						     MMC_SIGNAL_VOLTAGE_180, 0);
> > +			host->caps2&  MMC_CAP2_HS200_1_2V_SDR)
> > +		err = mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_120, 0);
> > +
> > +	if (err&&  card->ext_csd.card_type&  EXT_CSD_CARD_TYPE_SDR_1_8V&&
> > +			host->caps2&  MMC_CAP2_HS200_1_8V_SDR)
> > +		err = mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_180, 0);
> >
> >   	/* If fails try again during next card power cycle */
> >   	if (err)
> 
> --
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