linux-kernel - Re: [PATCH] [RFC] dmaengine: add fifo

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Message-ID: <98954eb3-21f1-6008-f8e1-f9f9b82f87fb@nvidia.com>
Date:   Wed, 31 Jul 2019 10:48:14 +0100
From:   Jon Hunter <jonathanh@...dia.com>
To:     Vinod Koul <vkoul@...nel.org>, Sameer Pujar <spujar@...dia.com>
CC:     Peter Ujfalusi <peter.ujfalusi@...com>, <dan.j.williams@...el.com>,
        <tiwai@...e.com>, <dmaengine@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <sharadg@...dia.com>,
        <rlokhande@...dia.com>, <dramesh@...dia.com>, <mkumard@...dia.com>
Subject: Re: [PATCH] [RFC] dmaengine: add fifo_size member


On 29/07/2019 07:10, Vinod Koul wrote:
> On 23-07-19, 11:24, Sameer Pujar wrote:
>>
>> On 7/19/2019 10:34 AM, Vinod Koul wrote:
>>> On 05-07-19, 11:45, Sameer Pujar wrote:
>>>> Hi Vinod,
>>>>
>>>> What are your final thoughts regarding this?
>>> Hi sameer,
>>>
>>> Sorry for the delay in replying
>>>
>>> On this, I am inclined to think that dma driver should not be involved.
>>> The ADMAIF needs this configuration and we should take the path of
>>> dma_router for this piece and add features like this to it
>>
>> Hi Vinod,
>>
>> The configuration is needed by both ADMA and ADMAIF. The size is
>> configurable
>> on ADMAIF side. ADMA needs to know this info and program accordingly.
> 
> Well I would say client decides the settings for both DMA, DMAIF and
> sets the peripheral accordingly as well, so client communicates the two
> sets of info to two set of drivers

That maybe, but I still don't see how the information is passed from the
client in the first place. The current problem is that there is no means
to pass both a max-burst size and fifo-size to the DMA driver from the
client.

IMO there needs to be a way to pass vendor specific DMA configuration
(if this information is not common) otherwise we just end up in a
scenario like there is for the xilinx DMA driver
(include/linux/dma/xilinx_dma.h) that has a custom API for passing this
information.

Cheers
Jon

-- 
nvpublic