Subject: [PATCH 3/4] dmaengine: qcom_bam_dma: use correct pipe FIFO size

From: [email-masked] (Stanimir Varbanov)
Date: Wed, 2 Dec 2015 18:44:11 +0200

On 12/01/2015 07:23 PM, Andy Gross wrote:
> On Tue, Dec 01, 2015 at 11:14:58AM +0200, Stanimir Varbanov wrote:
>> The pipe fifo size register must instruct the bam hw
>> how many hw descriptors can be pushed to fifo. Currently
>> we isntruct the hw with 32KBytes but wrap the tail in
>> bam_start_dma in BAM_P_EVNT_REG on 4095 i.e. 32760. This
>> leads to stalled transactions when the tail wraps.
>>
>> Fix this by use the correct fifo size in BAM_P_FIFO_SIZES
>> register i.e. 32K - 8.
>>
>> Signed-off-by: Stanimir Varbanov <[email-masked]>
>> ---
>>  drivers/dma/qcom_bam_dma.c |    2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/dma/qcom_bam_dma.c b/drivers/dma/qcom_bam_dma.c
>> index 0f06f3b7a72b..6d290de9ab2b 100644
>> --- a/drivers/dma/qcom_bam_dma.c
>> +++ b/drivers/dma/qcom_bam_dma.c
>> @@ -458,7 +458,7 @@ static void bam_chan_init_hw(struct bam_chan *bchan,
>>  	 */
>>  	writel_relaxed(ALIGN(bchan->fifo_phys, sizeof(struct bam_desc_hw)),
>>  			bam_addr(bdev, bchan->id, BAM_P_DESC_FIFO_ADDR));
>> -	writel_relaxed(BAM_DESC_FIFO_SIZE,
>> +	writel_relaxed(BAM_MAX_DATA_SIZE,
>>  			bam_addr(bdev, bchan->id, BAM_P_FIFO_SIZES));
> 
> This is just using the #define.  That is ok, but if you use this instead of the
> BAM_P_FIFO_SIZES then you need to fix your comment.  Or actually use the
> register value.... otherwise looks fine.

I did not follow your comment, but the intension of the patch is to set
the proper FIFO size in BAM_P_FIFO_SIZES register, i.e. 32K - 8.

-- 
regards,
Stan