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From:   Chuanhong Guo <gch981213@gmail.com>
Date:   Sat, 15 Feb 2020 15:06:05 +0800
Message-ID: <CAJsYDVJ9JGGpDm-FWvqDsS_ffwQ4FzY_cbVFpnEKt6B_Ab=TMQ@mail.gmail.com>
Subject: Re: [PATCH v2] mtd: mtk-quadspi: add support for DMA reading
To:     linux-mtd@lists.infradead.org
Cc:     Tudor Ambarus <tudor.ambarus@microchip.com>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org,
        open list <linux-kernel@vger.kernel.org>
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Hi all!

On Sat, Feb 8, 2020 at 4:41 PM Chuanhong Guo <gch981213@gmail.com> wrote:
>
> PIO reading mode on this controller is pretty inefficient
> (one cmd+addr+dummy sequence reads only one byte)
> This patch adds support for reading using DMA mode which increases
> reading speed from 1MB/s to 4MB/s
>
> DMA busy checking is implemented with readl_poll_timeout because
> I don't have access to IRQ-related docs. The speed increment comes
> from those saved cmd+addr+dummy clocks.
>
> This controller requires that DMA source/destination address and
> reading length should be 16-byte aligned. We use a bounce buffer if
> one of them is not aligned, read more than what we need, and copy
> data from corresponding buffer offset.
>
> Signed-off-by: Chuanhong Guo <gch981213@gmail.com>

This patch is deprecated. I wrote a new spi-mem driver for this
controller:
https://patchwork.ozlabs.org/project/linux-mtd/list/?series=158701
and will be focus on getting that one merged instead.
-- 
Regards,
Chuanhong Guo