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    SubjectRe: [PATCH] mmc: Test bus-width for old MMC devices (v2)
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    On Fri, Dec 17, 2010 at 3:11 AM, Takashi Iwai <tiwai@suse.de> wrote:
    > At Fri, 17 Dec 2010 03:43:42 +0000,
    > Chris Ball wrote:
    >>
    >> Hi Philip,
    >>
    >> On Thu, Dec 16, 2010 at 06:33:49PM -0800, Philip Rakity wrote:
    >> > It is not possible for bus_width to be not initialized.  This would imply ARRAY_SIZE(bus_widths) is 1.  Certainly not true.
    >>
    >> Right, I agree.  We should fix the warning anyway.
    >
    > Well, this is always a gray-zone question.  One prefers fixing it
    > either via uninitialized_var() or by setting a bogus value.  But, this
    > would cover any possible real bug in future.  Thus another prefers
    > ignoring it, because it's just a compiler bug (mostly of old gcc).
    >
    > After all, it's up to maintainer, so take as you like :)
    >
    >
    > thanks,
    >
    > Takashi
    >
    >
    >> > We could just initialize by changing
    >> > +           unsigned idx, bus_width;
    >> > to
    >> > +           unsigned idx, bus_width = 0;
    >>
    >> Okay, I've pushed to mmc-next with that change.
    >>
    >> > I wonder what compiler are you using so we can avoid this issue in future.
    >>
    >> Ah, good point -- I was building with a gcc 4.1.2 ARM cross-compiler,
    >> and using a gcc 4.5.1 cross-build instead avoids the warning.
    >>
    >> Thanks,
    >>
    >> --
    >> Chris Ball   <cjb@laptop.org>   <http://printf.net/>
    >> One Laptop Per Child
    >>
    >

    Could you help adding this modification?
    We found error happen since bus_width is not set at these condition:
    1. ddr=0
    2. not set MMC_CAP_BUS_WIDTH_TEST

    diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
    index 1d8409f..86cac0d 100644
    --- a/drivers/mmc/core/mmc.c
    +++ b/drivers/mmc/core/mmc.c
    @@ -586,7 +586,11 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
    } else if (ddr) {
    mmc_card_set_ddr_mode(card);
    mmc_set_bus_width_ddr(card->host, bus_width, ddr);
    - }
    +
    + } else
    + mmc_set_bus_width(card->host,
    + bus_widths[idx]);
    +
    }

    if (!oldcard)
    --
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