[U-Boot] [U-Boot, v3, 1/2] fs: fat: dynamically allocate memory for temporary buffer

[Marek Vasut]

On 2/21/19 9:44 AM, Alexander Graf wrote:
> 
> 
> On 21.02.19 09:41, Marek Vasut wrote:
>> On 2/21/19 9:40 AM, Chee, Tien Fong wrote:
>>> On Thu, 2019-02-21 at 09:29 +0100, Alexander Graf wrote:
>>>>
>>>> On 21.02.19 09:23, Chee, Tien Fong wrote:
>>>>>
>>>>> On Thu, 2019-02-21 at 08:45 +0100, Michal Simek wrote:
>>>>>>
>>>>>> Hi Tom,
>>>>>>
>>>>>> On 20. 02. 19 2:58, Tom Rini wrote:
>>>>>>>
>>>>>>>
>>>>>>> On Mon, Feb 11, 2019 at 02:56:19PM +0800, tien.fong.chee at intel.
>>>>>>> com
>>>>>>> wrote:
>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> From: Tien Fong Chee <tien.fong.chee at intel.com>
>>>>>>>>
>>>>>>>> Drop the statically allocated get_contents_vfatname_block and
>>>>>>>> dynamically allocate a buffer only if required. This saves
>>>>>>>> 64KiB of memory.
>>>>>>>>
>>>>>>>> Signed-off-by: Stefan Agner <stefan.ag... at toradex.com>
>>>>>>>> Signed-off-by: Tien Fong Chee <tien.fong.chee at intel.com>
>>>>>>> Applied to u-boot/master, thanks!
>>>>>> please remove this patch (better both of them because they were
>>>>>> in
>>>>>> series)
>>>>> I think patch 2/2 should be safe, because no memory size is
>>>>> changed.
>>>>> Basically, it just to release the allocated memory immediately when
>>>>> it's not required, so other can re-use it.
>>>>>
>>>>>>
>>>>>> because they are breaking at least ZynqMP SPL. It is also too
>>>>>> late in cycle to create random fix.
>>>>>>
>>>>>> You can't simply move 64KB from code to malloc without reflecting
>>>>>> this
>>>>>> by changing MALLOC space size.
>>>>>>
>>>>>> Other boards with SPL fat could be also affected by this if they
>>>>>> don't
>>>>>> allocate big malloc space.
>>>>> So, any suggestion to get the patch 1/2 accepted? inform all board
>>>>> maintainers to test it out?
>>>> You already received feedback that it does break ZynqMP, so the
>>>> current
>>>> approach won't work.
>>>>
>>>> How about you create a new kconfig option that allows you to say
>>>> whether
>>>> you want to use malloc or .bss for temporary data in the FAT driver.
>>>> You
>>>> can then have an _SPL_ version of that kconfig and check for it with
>>>> IS_ENABLED() which should automatically tell you the right answer
>>>> depending on whether you're in an SPL build or not.
>>>>
>>>> Then you can set the SPL version to default malloc and the non-SPL
>>>> version to default .bss.
>>> Marek and Tom rini,
>>>
>>> Are you guys okay with Alex's suggestion?
>>
>> I'm not a big fan of adding more and more ifdeffery.
>> Is there some other option ?
> 
> Is RAM up already at this point? Maybe we could improve the SPL malloc
> mechanism to move allocations into DRAM once it's available.

Well, the FAT buffers waste some 64kiB of bss, so we can use that area
for malloc instead, no ?

-- 
Best regards,
Marek Vasut