linux-kernel - Re: [PATCH v2 3/6] dmaengine: dw: Set DMA device max segment size parameter

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Message-ID: <5c83eabd-08c9-fdae-d13f-49c177b6c5bf@synopsys.com>
Date:   Fri, 8 May 2020 18:49:18 +0000
From:   Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Serge Semin <Sergey.Semin@...kalelectronics.ru>
CC:     Vinod Koul <vkoul@...nel.org>, Viresh Kumar <vireshk@...nel.org>,
        "Dan Williams" <dan.j.williams@...el.com>,
        Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Paul Burton <paulburton@...nel.org>,
        "Ralf Baechle" <ralf@...ux-mips.org>,
        Arnd Bergmann <arnd@...db.de>,
        Rob Herring <robh+dt@...nel.org>,
        "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        arcml <linux-snps-arc@...ts.infradead.org>
Subject: Re: [PATCH v2 3/6] dmaengine: dw: Set DMA device max segment size
 parameter

On 5/8/20 4:21 AM, Andy Shevchenko wrote:
> Yeah, I have locally something like this and I didn't dare to upstream because
> there is an issue. We have this information per DMA controller, while we
> actually need this on per DMA channel basis.
>
> Above will work only for synthesized DMA with all channels having same block
> size. That's why above conditional is not needed anyway.
>
> OTOH, I never saw the DesignWare DMA to be synthesized differently (I remember
> that Intel Medfield has interesting settings, but I don't remember if DMA
> channels are different inside the same controller).
>
> Vineet, do you have any information that Synopsys customers synthesized DMA
> controllers with different channel characteristics inside one DMA IP?

The IP drivers are done by different teams, but I can try and ask around.