linux-kernel - Re: [PATCH] dmaengine: qcom-bam: fix circular buffer handling

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Message-ID: <a50066ac-be85-6706-e7f3-f1069fd0dd0b@codeaurora.org>
Date:   Tue, 18 Jun 2019 21:57:49 +0530
From:   Sricharan R <sricharan@...eaurora.org>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        vkoul@...nel.org
Cc:     dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH] dmaengine: qcom-bam: fix circular buffer handling



On 6/18/2019 8:42 PM, Srinivas Kandagatla wrote:
> 
> 
> On 18/06/2019 15:56, Sricharan R wrote:
>>    So MAX_DESCRIPTORS is used in driver for masking head/tail pointers.
>>    That's why we have to pass MAX_DESCRIPTORS + 1 so that it works
>>    when the Macros does a size - 1
> Isn't that incorrect to do that, pretending to have more descriptors than we actually have?
> 

 The Macro's expect that buffer size is power of 2. So we are infact passing the actual correct
 size ( MAX_DESCRIPTORS + 1 = 4096)

Regards,
 Sricharan

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