Messages in this thread | | | Date | Thu, 7 Sep 2017 09:12:51 +0200 | From | Boris Brezillon <> | Subject | Re: [PATCH] mtd: spi-nor: fix DMA unsafe buffer issue in spi_nor_read_sfdp() |
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On Thu, 7 Sep 2017 00:50:12 +0200 Cyrille Pitchen <cyrille.pitchen@wedev4u.fr> wrote:
> Le 06/09/2017 à 23:45, Cyrille Pitchen a écrit : > > spi_nor_read_sfdp() calls nor->read() to read the SFDP data. > > When the m25p80 driver is used (pretty common case), nor->read() is then > > implemented by the m25p80_read() function, which is likely to initialize a > > 'struct spi_transfer' from its buf argument before appending this > > structure inside the 'struct spi_message' argument of spi_sync(). > > > > Besides the SPI sub-system states that both .tx_buf and .rx_buf members of > > 'struct spi_transfer' must point into dma-safe memory. However, two of the > > three calls of spi_nor_read_sfdp() were given pointers to stack allocated > > memory as buf argument, hence not in a dma-safe area. > > Hopefully, the third and last call of spi_nor_read_sfdp() was already > > given a kmalloc'ed buffer argument, hence dma-safe. > > > > So this patch fixes this issue by introducing a > > spi_nor_read_sfdp_dma_unsafe() function which simply wraps the existing > > spi_nor_read_sfdp() function and uses some kmalloc'ed memory as a bounce > > buffer. > > > > Reported-by: Geert Uytterhoeven <geert@linux-m68k.org> > > Signed-off-by: Cyrille Pitchen <cyrille.pitchen@wedev4u.fr> > > --- > > > > Compiled but not tested yet! > > tested on a sama5d2 xplained board with: > - an Adesto at25df321a on spi0 (using the m25p80.c driver) > - a Macronix mx25l25673g on qspi0 (using the atmel-quadspi.c driver)
Cool, that was fast.
> > applied on the spi-nor/next branch of l2-mtd
Maybe a bit too fast. You should leave at least one day to reviewers/testers before applying the patch.
BTW, I was planning on taking the patch directly.
> > should be quickly sent as a fix to the MTD pull-request for 4.14 > > Sorry for that! > > > > > drivers/mtd/spi-nor/spi-nor.c | 36 +++++++++++++++++++++++++++++++++--- > > 1 file changed, 33 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c > > index cf1d4a15e10a..05254dd6a4a0 100644 > > --- a/drivers/mtd/spi-nor/spi-nor.c > > +++ b/drivers/mtd/spi-nor/spi-nor.c > > @@ -1784,7 +1784,7 @@ spi_nor_set_pp_settings(struct spi_nor_pp_command *pp, > > * @nor: pointer to a 'struct spi_nor' > > * @addr: offset in the SFDP area to start reading data from > > * @len: number of bytes to read > > - * @buf: buffer where the SFDP data are copied into > > + * @buf: buffer where the SFDP data are copied into (dma-safe memory) > > * > > * Whatever the actual numbers of bytes for address and dummy cycles are > > * for (Fast) Read commands, the Read SFDP (5Ah) instruction is always > > @@ -1829,6 +1829,36 @@ static int spi_nor_read_sfdp(struct spi_nor *nor, u32 addr, > > return ret; > > } > > > > +/** > > + * spi_nor_read_sfdp_dma_unsafe() - read Serial Flash Discoverable Parameters. > > + * @nor: pointer to a 'struct spi_nor' > > + * @addr: offset in the SFDP area to start reading data from > > + * @len: number of bytes to read > > + * @buf: buffer where the SFDP data are copied into > > + * > > + * Wrap spi_nor_read_sfdp() using a kmalloc'ed bounce buffer as @buf is now not > > + * guaranteed to be dma-safe. > > + * > > + * Return: -ENOMEM if kmalloc() fails, the return code of spi_nor_read_sfdp() > > + * otherwise. > > + */ > > +static int spi_nor_read_sfdp_dma_unsafe(struct spi_nor *nor, u32 addr, > > + size_t len, void *buf) > > +{ > > + void *dma_safe_buf; > > + int ret; > > + > > + dma_safe_buf = kmalloc(len, GFP_KERNEL); > > + if (!dma_safe_buf) > > + return -ENOMEM; > > + > > + ret = spi_nor_read_sfdp(nor, addr, len, dma_safe_buf); > > + memcpy(buf, dma_safe_buf, len); > > + kfree(dma_safe_buf); > > + > > + return ret; > > +} > > + > > struct sfdp_parameter_header { > > u8 id_lsb; > > u8 minor; > > @@ -2101,7 +2131,7 @@ static int spi_nor_parse_bfpt(struct spi_nor *nor, > > bfpt_header->length * sizeof(u32)); > > addr = SFDP_PARAM_HEADER_PTP(bfpt_header); > > memset(&bfpt, 0, sizeof(bfpt)); > > - err = spi_nor_read_sfdp(nor, addr, len, &bfpt); > > + err = spi_nor_read_sfdp_dma_unsafe(nor, addr, len, &bfpt); > > if (err < 0) > > return err; > > > > @@ -2243,7 +2273,7 @@ static int spi_nor_parse_sfdp(struct spi_nor *nor, > > int i, err; > > > > /* Get the SFDP header. */ > > - err = spi_nor_read_sfdp(nor, 0, sizeof(header), &header); > > + err = spi_nor_read_sfdp_dma_unsafe(nor, 0, sizeof(header), &header); > > if (err < 0) > > return err; > > > > >
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