RE: [PATCH v1 2/3] mmc: sdio: Fix SDIO 3.0 UHS-I initialization sequence

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Hi Bing,

sdhci_add_host() reads host controller's capabilities and initialize host->caps of function mmc_host_uhs(). So mmc_host_uhs() only return this cached values.

Thanks,
Jackey

-----Original Message-----
From: Bing Zhao [mailto:bzhao@xxxxxxxxxxx] 
Sent: Thursday, December 06, 2012 3:14 AM
To: Shen, Jackey; Subhash Jadavani; linux-mmc@xxxxxxxxxxxxxxx
Cc: linux-arm-msm@xxxxxxxxxxxxxxx; Sujit Reddy Thumma
Subject: RE: [PATCH v1 2/3] mmc: sdio: Fix SDIO 3.0 UHS-I initialization sequence

Hi Jackey,

> Hi Bing,
> 
> The function mmc_host_uhs() will return false and never set bit[24] (S18R) for SDIO 2.0 cards.

I thought mmc_host_uhs() will return host controller's capabilities, no?

Thanks,
Bing

> 
> Thanks,
> Jackey
> 
> -----Original Message-----
> From: linux-mmc-owner@xxxxxxxxxxxxxxx 
> [mailto:linux-mmc-owner@xxxxxxxxxxxxxxx] On Behalf Of Bing Zhao
> Sent: Wednesday, December 05, 2012 5:14 AM
> To: Subhash Jadavani; linux-mmc@xxxxxxxxxxxxxxx
> Cc: linux-arm-msm@xxxxxxxxxxxxxxx; Sujit Reddy Thumma
> Subject: RE: [PATCH v1 2/3] mmc: sdio: Fix SDIO 3.0 UHS-I 
> initialization sequence
> 
> Hi,
> 
> > From: Sujit Reddy Thumma <sthumma@xxxxxxxxxxxxxx>
> >
> > According to UHS-I initialization sequence for SDIO 3.0 cards, the 
> > host must set bit[24] (S18R) of OCR register during OCR handshake to 
> > know whether the SDIO card is capable of doing 1.8V I/O.
> 
> In SDIO 2.0 spec, bit[24] is reserved, "shall be set to 0".
> Setting it to 1 might cause side effect to 2.0 cards.
> Perhaps using a quirk for S18R is more suitable for all combinations.
> 
> Regards,
> Bing
> 
> >
> > Signed-off-by: Sujit Reddy Thumma <sthumma@xxxxxxxxxxxxxx>
> > Signed-off-by: Subhash Jadavani <subhashj@xxxxxxxxxxxxxx>
> > ---
> >  drivers/mmc/core/sdio.c  |   22 +++++++++++-----------
> >  include/linux/mmc/host.h |    8 ++++++++
> >  2 files changed, 19 insertions(+), 11 deletions(-)
> 
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