linux-kernel - Re: [PATCH 1/2] mtd: mtk-quadspi: add support for memory-mapped flash reading

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Date:   Thu, 7 Nov 2019 23:34:49 +0800
From:   Chuanhong Guo <gch981213@...il.com>
To:     Yingjoe Chen <yingjoe.chen@...iatek.com>
Cc:     linux-mtd@...ts.infradead.org, Mark Rutland <mark.rutland@....com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Vignesh Raghavendra <vigneshr@...com>,
        Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Richard Weinberger <richard@....at>,
        open list <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        linux-mediatek@...ts.infradead.org,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Brian Norris <computersforpeace@...il.com>,
        David Woodhouse <dwmw2@...radead.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/2] mtd: mtk-quadspi: add support for memory-mapped flash reading

Hi!

On Thu, Nov 7, 2019 at 9:23 PM Yingjoe Chen <yingjoe.chen@...iatek.com> wrote:
>
> On Wed, 2019-11-06 at 22:07 +0800, Chuanhong Guo wrote:
> > PIO reading mode on this controller is ridiculously inefficient
> > (one cmd+addr+dummy sequence reads only one byte)
> > This patch adds support for reading from memory-mapped flash area
> > which increases reading speed from 1MB/s to 5.6MB/s
>
> This may not be true for all MTK SoC. Which one are you testing?
>

I tested it on MT7629.
There should be a 5x reading speed increment under DMA or direct read
mode than PIO mode because PIO mode needs 30 or 36 clocks for every
single byte of data while DMA or direct read only needs 24 or 30
clocks for initial command/address/dummy and every byte of data after
that only need 8 clocks.

Regards,
Chuanhong Guo