From: Boris Brezillon <boris.brezillon@free-electrons.com>
To: Cyrille Pitchen <cyrille.pitchen@atmel.com>
Cc: Richard Weinberger <richard@nod.at>, Vignesh R <vigneshr@ti.com>,
David Woodhouse <dwmw2@infradead.org>,
Brian Norris <computersforpeace@gmail.com>,
Marek Vasut <marek.vasut@gmail.com>,
<linux-mtd@lists.infradead.org>, <linux-kernel@vger.kernel.org>,
<linux-omap@vger.kernel.org>,
Frode Isaksen <fisaksen@baylibre.com>,
<linux-spi@vger.kernel.org>
Subject: Re: [RFC PATCH 1/2] mtd: spi-nor: Introduce bounce buffer to handle vmalloc'd buffers
Date: Wed, 1 Mar 2017 11:18:05 +0100 [thread overview]
Message-ID: <20170301111805.0eb23b76@bbrezillon> (raw)
In-Reply-To: <65b4a156-f2a8-4c5e-4399-2024a147d5ec@atmel.com>
On Wed, 1 Mar 2017 11:09:57 +0100
Cyrille Pitchen <cyrille.pitchen@atmel.com> wrote:
> Le 28/02/2017 à 22:39, Richard Weinberger a écrit :
> > Vignesh,
> >
> > Am 27.02.2017 um 13:08 schrieb Vignesh R:
> >> Filesystems like UBIFS may pass vmalloc'd buffers to SPI NOR layer which
> >> will end up in SPI layer. SPI core does try to handle such buffers (see
> >> spi_map_buf()) by doing vmalloc_to_page() and creating scatterlist. But,
> >> its known that this does not work well with VIVT/aliasing cache
> >> architectures.
> >> This also fails when buffers are addressed using LPAE (buffers in region
> >> higher than 32 bit addressable region), if DMA is 32bit only.
> >>
> >> Introduce bounce buffers support in SPI NOR framework to handle
> >> vmalloc'd buffers. Use a pre-allocated per flash bounce buffer equal to
> >> the sector size of the flash. Flash drivers can enable this feature by
> >> setting SNOR_F_USE_BOUNCE_BUFFER flag.
> >> This would also enable SPI NOR drivers to safely use DMA in their
> >> read/write callbacks.
> >>
> >> Signed-off-by: Vignesh R <vigneshr@ti.com>
> >> ---
> >> drivers/mtd/spi-nor/spi-nor.c | 30 +++++++++++++++++++++++++++---
> >> include/linux/mtd/spi-nor.h | 4 ++++
> >> 2 files changed, 31 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> >> index 747645c74134..c241fefa5aff 100644
> >> --- a/drivers/mtd/spi-nor/spi-nor.c
> >> +++ b/drivers/mtd/spi-nor/spi-nor.c
> >> @@ -17,6 +17,7 @@
> >> #include <linux/mutex.h>
> >> #include <linux/math64.h>
> >> #include <linux/sizes.h>
> >> +#include <linux/mm.h>
> >>
> >> #include <linux/mtd/mtd.h>
> >> #include <linux/of_platform.h>
> >> @@ -1205,11 +1206,21 @@ static int spi_nor_read(struct mtd_info *mtd, loff_t from, size_t len,
> >>
> >> while (len) {
> >> loff_t addr = from;
> >> + bool use_bb = false;
> >> + u_char *dst_buf = buf;
> >> + size_t buf_len = len;
> >>
> >> if (nor->flags & SNOR_F_S3AN_ADDR_DEFAULT)
> >> addr = spi_nor_s3an_addr_convert(nor, addr);
> >>
> >> - ret = nor->read(nor, addr, len, buf);
> >> + if (!virt_addr_valid(buf) && nor->bounce_buf) {
>
> Should we use is_vmalloc_addr() instead of virt_addr_valid() ?
>
> I guess virt_addr_valid() returns true even for kmalloc'ed buffers
> however the copy into the bounce buffer should be avoided for kmalloc'ed
> memory.
The test is !virt_addr_valid(), so we won't use the bounce buffer for
kmalloc-ed regions. I don't remember why we use virt_addr_valid()
instead of is_vmalloc_addr() in the NAND framework, but there was a
good reason (virt_addr_valid() is more restrictive, but I don't
remember why it's safer :))
next prev parent reply other threads:[~2017-03-01 10:26 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-27 12:08 [RFC PATCH 0/2] mtd: spi-nor: Handle vmalloc'd buffers Vignesh R
2017-02-27 12:08 ` [RFC PATCH 1/2] mtd: spi-nor: Introduce bounce buffer to handle " Vignesh R
2017-02-28 21:39 ` Richard Weinberger
2017-03-01 5:13 ` Vignesh R
2017-03-01 10:09 ` Cyrille Pitchen
2017-03-01 10:18 ` Boris Brezillon [this message]
2017-03-01 11:18 ` Frode Isaksen
2017-03-01 12:12 ` Boris Brezillon
2017-03-01 11:50 ` Vignesh R
2017-02-27 12:08 ` [RFC PATCH 2/2] mtd: devices: m25p80: Enable spi-nor bounce buffer support Vignesh R
2017-02-28 21:41 ` Richard Weinberger
2017-03-01 4:54 ` Vignesh R
2017-03-01 10:43 ` Cyrille Pitchen
2017-03-01 11:14 ` Frode Isaksen
2017-03-01 11:46 ` Vignesh R
2017-03-01 12:23 ` Boris Brezillon
2017-03-01 14:21 ` Cyrille Pitchen
2017-03-01 14:28 ` Boris Brezillon
2017-03-01 14:30 ` Cyrille Pitchen
2017-03-01 15:52 ` Mark Brown
2017-03-01 16:04 ` Boris Brezillon
2017-03-01 16:55 ` Boris Brezillon
2017-03-02 9:06 ` Frode Isaksen
2017-03-02 13:54 ` Vignesh R
2017-03-02 14:29 ` Boris Brezillon
2017-03-02 15:03 ` Frode Isaksen
2017-03-02 15:25 ` Boris Brezillon
2017-03-03 9:02 ` Frode Isaksen
2017-03-02 16:45 ` Cyrille Pitchen
2017-03-02 17:00 ` Mark Brown
2017-03-02 19:49 ` Boris Brezillon
2017-03-03 12:50 ` Mark Brown
2017-03-06 11:47 ` Vignesh R
2017-03-14 13:21 ` Vignesh R
2017-02-27 14:03 ` [RFC PATCH 0/2] mtd: spi-nor: Handle vmalloc'd buffers Frode Isaksen
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