From: Arnd Bergmann <arnd@arndb.de>
To: linux-arm-kernel@lists.infradead.org
Cc: Boris Brezillon <boris.brezillon@free-electrons.com>,
David Woodhouse <dwmw2@infradead.org>,
Brian Norris <computersforpeace@gmail.com>,
linux-mtd@lists.infradead.org,
Maxime Ripard <maxime.ripard@free-electrons.com>,
stable@vger.kernel.org, linux-sunxi@googlegroups.com
Subject: Re: [PATCH v4] mtd: nand: sunxi: fix OOB handling in ->write_xxx() functions
Date: Mon, 14 Sep 2015 10:59:02 +0200 [thread overview]
Message-ID: <1472478.qiY0UY0ao8@wuerfel> (raw)
In-Reply-To: <1442220063-7520-1-git-send-email-boris.brezillon@free-electrons.com>
On Monday 14 September 2015 10:41:03 Boris Brezillon wrote:
> /* Fill OOB data in */
> - if (oob_required) {
> - tmp = 0xffffffff;
> - memcpy_toio(nfc->regs + NFC_REG_USER_DATA_BASE, &tmp,
> - 4);
> - } else {
> - memcpy_toio(nfc->regs + NFC_REG_USER_DATA_BASE,
> - chip->oob_poi + offset - mtd->writesize,
> - 4);
> - }
> + writel(NFC_BUF_TO_USER_DATA(chip->oob_poi +
> + layout->oobfree[i].offset),
> + nfc->regs + NFC_REG_USER_DATA_BASE);
This looks like you are changing the endianess of the data that gets written.
Is that intentional?
memcpy_toio() uses the same endianess for source and destination, while writel()
assumes that the destination is a little-endian register, and that could break
if the kernel is built to run as big-endian. I also see that sunxi_nfc_write_buf()
uses memcpy_toio() for writing the actual data, and you are not changing that.
If all hardware can do 32-bit accesses here and the size is guaranteed to be a
multiple of four bytes, you can probably improve performance by using a
__raw_writel() loop there. Using __raw_writel() in general is almost always
a bug, but here it actually makes sense. See also the powerpc implementation
of _memcpy_toio().
Arnd
WARNING: multiple messages have this Message-ID (diff)
From: arnd@arndb.de (Arnd Bergmann)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v4] mtd: nand: sunxi: fix OOB handling in ->write_xxx() functions
Date: Mon, 14 Sep 2015 10:59:02 +0200 [thread overview]
Message-ID: <1472478.qiY0UY0ao8@wuerfel> (raw)
In-Reply-To: <1442220063-7520-1-git-send-email-boris.brezillon@free-electrons.com>
On Monday 14 September 2015 10:41:03 Boris Brezillon wrote:
> /* Fill OOB data in */
> - if (oob_required) {
> - tmp = 0xffffffff;
> - memcpy_toio(nfc->regs + NFC_REG_USER_DATA_BASE, &tmp,
> - 4);
> - } else {
> - memcpy_toio(nfc->regs + NFC_REG_USER_DATA_BASE,
> - chip->oob_poi + offset - mtd->writesize,
> - 4);
> - }
> + writel(NFC_BUF_TO_USER_DATA(chip->oob_poi +
> + layout->oobfree[i].offset),
> + nfc->regs + NFC_REG_USER_DATA_BASE);
This looks like you are changing the endianess of the data that gets written.
Is that intentional?
memcpy_toio() uses the same endianess for source and destination, while writel()
assumes that the destination is a little-endian register, and that could break
if the kernel is built to run as big-endian. I also see that sunxi_nfc_write_buf()
uses memcpy_toio() for writing the actual data, and you are not changing that.
If all hardware can do 32-bit accesses here and the size is guaranteed to be a
multiple of four bytes, you can probably improve performance by using a
__raw_writel() loop there. Using __raw_writel() in general is almost always
a bug, but here it actually makes sense. See also the powerpc implementation
of _memcpy_toio().
Arnd
next prev parent reply other threads:[~2015-09-14 8:59 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-14 8:41 [PATCH v4] mtd: nand: sunxi: fix OOB handling in ->write_xxx() functions Boris Brezillon
2015-09-14 8:41 ` Boris Brezillon
2015-09-14 8:59 ` Arnd Bergmann [this message]
2015-09-14 8:59 ` Arnd Bergmann
2015-09-14 9:41 ` Boris Brezillon
2015-09-14 9:41 ` Boris Brezillon
2015-09-14 11:49 ` Arnd Bergmann
2015-09-14 11:49 ` Arnd Bergmann
2015-09-14 12:36 ` Arnd Bergmann
2015-09-14 12:36 ` Arnd Bergmann
2015-09-14 17:02 ` Brian Norris
2015-09-14 17:02 ` Brian Norris
2015-09-21 20:43 ` Brian Norris
2015-09-21 20:43 ` Brian Norris
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