[U-Boot] [PATCH] mmc: dw_mmc: Round up descriptor end to nearest multiple of cacheline size

[Marek Vasut]

On 4/1/19 8:57 PM, Simon Glass wrote:
> Hi Marek,
> 
> On Sat, 30 Mar 2019 at 20:37, Marek Vasut <marex at denx.de> wrote:
>>
>> On 3/30/19 10:18 PM, Simon Glass wrote:
>>> Hi Marek,
>>>
>>> On Sat, 23 Mar 2019 at 11:55, Marek Vasut <marex at denx.de> wrote:
>>>>
>>>> The driver currently calculates the end address of cache flush operation
>>>> for the DMA descriptors by adding cacheline size to the start address of
>>>> the last DMA descriptor. This is not safe, as the cacheline size may be,
>>>> in some unlikely cases, smaller than the DMA descriptor size. Replace the
>>>> addition with roundup() applied on the end address of the last DMA
>>>> descriptor to round it up to the nearest cacheline size multiple.
>>>>
>>>> Signed-off-by: Marek Vasut <marex at denx.de>
>>>> Cc: Jaehoon Chung <jh80.chung at samsung.com>
>>>> Cc: Simon Glass <sjg at chromium.org>
>>>> ---
>>>>  drivers/mmc/dw_mmc.c | 4 ++--
>>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/mmc/dw_mmc.c b/drivers/mmc/dw_mmc.c
>>>> index 72570235cb..bec30b1479 100644
>>>> --- a/drivers/mmc/dw_mmc.c
>>>> +++ b/drivers/mmc/dw_mmc.c
>>>> @@ -74,15 +74,15 @@ static void dwmci_prepare_data(struct dwmci_host *host,
>>>>                 dwmci_set_idma_desc(cur_idmac, flags, cnt,
>>>>                                     (ulong)bounce_buffer + (i * PAGE_SIZE));
>>>>
>>>> +               cur_idmac++;
>>>
>>> What is this change for? I don't see it mentioned above.
>>
>> AFAIR you need to increment the pointer to cur_idmac before breaking out
>> of the loop, otherwise data_end might point a bit before the actual end
>> of the buffer.
> 
> OK is that fixing a bug? Should it be in a different commit, or
> mentioned in this commit message?

I think if you have a really small cachelines, smaller than the idmac
structure, this will trigger a bug.

-- 
Best regards,
Marek Vasut