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

Philip Rakity
2010-12-21T16:39:34Z

Can you please try this diff and see if it works for you.

Will do formal patch after your testing. What card is failing ?

Please let me know the manufacturing information so can add card to my test suite.

Philip

diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 1d8409f..77072c8 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -558,6 +558,8 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
EXT_CSD_BUS_WIDTH,
ext_csd_bits[idx][0]);
if (!err) {
+ mmc_set_bus_width_ddr(card->host,
+ bus_width, MMC_SDR_MODE);
/*
* If controller can't handle bus width test,
* use the highest bus width to maintain
@@ -565,8 +567,6 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
*/
if (!(host->caps & MMC_CAP_BUS_WIDTH_TEST))
break;
- mmc_set_bus_width_ddr(card->host,
- bus_width, MMC_SDR_MODE);
err = mmc_bus_test(card, bus_width);
if (!err)
break;
@@ -586,7 +586,8 @@ 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_width);
}

if (!oldcard)

Philip

On Dec 21, 2010, at 2:59 AM, zhangfei gao wrote:

> 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)