Re: [PATCH] mmc: Test bus-width for old MMC devices (v2)

zhangfei gao
2010-12-21T10:59:10Z

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)