Re: [PATCH] ath6kl: Use mutex to protect dma buffer in sync read write

[Kalle Valo <kvalo@qca.qualcomm.com>]

On 11/21/2011 08:56 AM, Raja Mani wrote:
> Firmware crashes while starting Soft AP in 32 bit x86 platform.
> The reason is that the single dma buffer (ar_sdio->dma_buffer)
> is used in ath6kl_sdio_read_write_sync() for unaligned buffer
> handling and this function is called in the multiple context
> at the same time. So, finally hits dma buffer corruption and
> firmware crash.
> 
> Mutex is used to protect dma buffer to avoid data corruption.
> Spin lock can not used to fix this issue since mmc stack
> read/write calls may for sleep.
> 
> Observed this issue with recently commited patch
> "ath6kl: Claim sdio function only at appropriate places"
> 861dd058f495973c7ad2a44b8f68f3cc05733eab
> 
> Signed-off-by: Raja Mani <rmani@qca.qualcomm.com>

I really would not like to add yet another lock (or mutex) to ath6kl,
but I don't see any other quick fix for this. So I have applied this for
now, but I hope that in the future we get to remove the ugly bounce
buffer altogether.

But I did minor changes in the patch: I added a comment to the mutex
(which I now require for all new locks), renamed the lock to something
easier and moved it after the buffer.

Kalle