Re: [PATCH] dmaengine: qcom-bam: fix circular buffer handling
From: Sricharan R
Date: Wed Jun 19 2019 - 13:55:33 EST
On 6/18/2019 10:20 PM, Srinivas Kandagatla wrote:
> On 18/06/2019 17:27, Sricharan R wrote:
>> Â The Macro's expect that buffer size is power of 2. So we are infact passing the actual correct
>> Â size ( MAX_DESCRIPTORS + 1 = 4096)
> This will make the circular buffer macros happy but question is that do we actually have that many descriptor buffers?
> This is what is in the driver:
> #define BAM_DESC_FIFO_SIZEÂÂÂ SZ_32K
> #define MAX_DESCRIPTORS (BAM_DESC_FIFO_SIZE / sizeof(struct bam_desc_hw) - 1)
> #define BAM_FIFO_SIZEÂÂÂ (SZ_32K - 8)
> Wouldn't having MAX_DESCRIPTORS + 1 = 4096Â lead to overflow the actual descriptor memory size of (SZ_32K - 8) ?
Right, but the CIRC_SPACE macro assumes there is 1 space less than the actual size.
That said, agree there is an issue on the boundary. I will also do some testing tomorrow
on this and get back.
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