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

From: Chuanhong Guo <gch981213@gmail.com>
To: Vignesh Raghavendra <vigneshr@ti.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
	<devicetree@vger.kernel.org>,
	Tudor Ambarus <tudor.ambarus@microchip.com>,
	Richard Weinberger <richard@nod.at>,
	open list <linux-kernel@vger.kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	linux-mtd@lists.infradead.org,
	Miquel Raynal <miquel.raynal@bootlin.com>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	linux-mediatek@lists.infradead.org,
	Brian Norris <computersforpeace@gmail.com>,
	David Woodhouse <dwmw2@infradead.org>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/2] mtd: mtk-quadspi: add support for memory-mapped flash reading
Date: Thu, 7 Nov 2019 17:31:35 +0800	[thread overview]
Message-ID: <CAJsYDVJgUNxLhcO9iLKwRZHPQ9FT8XuKQq8ru_djD2nryT5o9A@mail.gmail.com> (raw)
In-Reply-To: <bc917a56-e688-d701-2279-87df460d6055@ti.com>

Hi!

On Thu, Nov 7, 2019 at 2:05 PM Vignesh Raghavendra <vigneshr@ti.com> wrote:
> > @@ -272,6 +273,11 @@ static ssize_t mtk_nor_read(struct spi_nor *nor, loff_t from, size_t length,
> >       mtk_nor_set_read_mode(mtk_nor);
> >       mtk_nor_set_addr(mtk_nor, addr);
> >
> > +     if (mtk_nor->flash_base) {
> > +             memcpy_fromio(buffer, mtk_nor->flash_base + from, length);
> > +             return length;
> > +     }
> > +
>
> Don't you need to check if access is still within valid memory mapped
> window?

The mapped area is 256MB and I don't quite believe there will be such
a big NOR flash.
I'll add a check here in the next version.

>
> >       for (i = 0; i < length; i++) {
> >               ret = mtk_nor_execute_cmd(mtk_nor, MTK_NOR_PIO_READ_CMD);
> >               if (ret < 0)
> > @@ -475,6 +481,11 @@ static int mtk_nor_drv_probe(struct platform_device *pdev)
> >       if (IS_ERR(mtk_nor->base))
> >               return PTR_ERR(mtk_nor->base);
> >
> > +     res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
> > +     mtk_nor->flash_base = devm_ioremap_resource(&pdev->dev, res);
>
> There is a single API now: devm_platform_ioremap_resource().

Cool. I'll change it.
Should I add another patch to change the same mapping operation right
above this piece of code?

Regards,
Chuanhong Guo

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