> -----Original Message-----
> From: Seungwon Jeon [mailto:tgih....@samsung.com]
> Sent: Wednesday, April 25, 2012 10:46 AM
> To: 'Subhash Jadavani'
> Cc: linux-mmc@vger.kernel.org; 'Chris Ball'; 'Girish K S'
> Subject: RE: [PATCH 2/2] mmc: core: fix the signaling 1.8V for HS200
>
> Subhash Jadavani <subha...@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.
Thanks for clarification. I was assuming that most of the devices will have I/O
voltage always set to 1.8v by host (when device is powered up) but yes,
according to spec, it's possible that I/O may be at 3.3v (high voltage) as well.
This patch looks good to me.
Reviewed-by: Subhash Jadavani <subha...@codeaurora.org>
Regards,
Subhash
>
> 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....@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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