linux-kernel - Re: [PATCH 4/4] spi: s3c64xx: Fix large transfers with DMA

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Date:   Mon, 26 Sep 2022 15:42:30 +0200
From:   Vincent Whitchurch <vincent.whitchurch@...s.com>
To:     Mark Brown <broonie@...nel.org>
CC:     <krzysztof.kozlowski@...aro.org>, <andi@...zian.org>,
        <kernel@...s.com>, <alim.akhtar@...sung.com>,
        <linux-spi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-samsung-soc@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 4/4] spi: s3c64xx: Fix large transfers with DMA

On Mon, Sep 19, 2022 at 03:38:29PM +0100, Mark Brown wrote:
> On Fri, Sep 16, 2022 at 01:39:51PM +0200, Vincent Whitchurch wrote:
> > The COUNT_VALUE in the PACKET_CNT register is 16-bit so the maximum
> > value is 65535.  Asking the driver to transfer a larger size currently
> > leads to the DMA transfer timing out.  Fix this by splitting the
> > transfer as needed.
> 
> The driver should just set max_transfer_size and let the core
> handle this.

Hmm, AFAICS, the core doesn't actually do anything with
max_transfer_size?  It's only used from spi-mem and a handful of other
clients via spi_max_transfer_size().