linux-kernel - Re: [PATCH v2] spi: spi-mtk-nor: fix timeout calculation overflow

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Date:   Tue, 22 Sep 2020 20:18:27 +0800
From:   Chuanhong Guo <gch981213@...il.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     linux-spi@...r.kernel.org,
        Bayi Cheng (程八意) 
        <bayi.cheng@...iatek.com>, stable@...r.kernel.org,
        Matthias Brugger <matthias.bgg@...il.com>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] spi: spi-mtk-nor: fix timeout calculation overflow

Hi!

On Tue, Sep 22, 2020 at 8:02 PM Mark Brown <broonie@...nel.org> wrote:
>
> On Tue, Sep 22, 2020 at 07:49:02PM +0800, Chuanhong Guo wrote:
>
> >               if ((op->data.dir == SPI_MEM_DATA_IN) &&
> >                   mtk_nor_match_read(op)) {
> > +                     // limit size to prevent timeout calculation overflow
> > +                     if (op->data.nbytes > 0x400000)
> > +                             op->data.nbytes = 0x400000;
>
> If there's a limit on transfer sizes there should also be a
> max_transfer_size or max_message_size set (which we should pay attention
> to in the core for flash stuff but IIRC we didn't do that yet).

There's already a 6-byte max_message_size limit on this controller.
spi-mem dma read is the only operation which allows such a long transfer.

-- 
Regards,
Chuanhong Guo