linux-kernel - Re: [PATCH v7 04/11] dmaengine: Introduce max SG list entries capability

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Message-ID: <20200715111315.GK34333@vkoul-mobl>
Date:   Wed, 15 Jul 2020 16:43:15 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Peter Ujfalusi <peter.ujfalusi@...com>,
        Serge Semin <fancer.lancer@...il.com>,
        Viresh Kumar <vireshk@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Arnd Bergmann <arnd@...db.de>,
        Rob Herring <robh+dt@...nel.org>, linux-mips@...r.kernel.org,
        devicetree@...r.kernel.org, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 04/11] dmaengine: Introduce max SG list entries
 capability

On 10-07-20, 19:14, Serge Semin wrote:
> On Fri, Jul 10, 2020 at 02:51:33PM +0300, Peter Ujfalusi wrote:

> > Since we should be able to handle longer lists and this is kind of a
> > hint for clients that above this number of nents the list will be broken
> > up to smaller 'bursts', which when traversing could cause latency.
> > 
> > sg_chunk_len might be another candidate.
> 
> Ok. We've got four candidates:
> - max_sg_nents_burst
> - max_sg_burst
> - max_sg_chain
> - sg_chunk_len
> 
> @Vinod, @Andy, what do you think?

So IIUC your hw supports single sg and in that you would like to publish
the length of each chunk, is that correct? If so sg_chunk_len seems
apt..

-- 
~Vinod