From: Boris Brezillon <boris.brezillon@bootlin.com>
To: <Tudor.Ambarus@microchip.com>
Cc: <marek.vasut@gmail.com>, <dwmw2@infradead.org>,
<computersforpeace@gmail.com>, <richard@nod.at>,
<linux-mtd@lists.infradead.org>, <linux-kernel@vger.kernel.org>,
<yogeshnarayan.gaur@nxp.com>, <cyrille.pitchen@wedev4u.fr>
Subject: Re: [PATCH 5/7] mtd: spi_nor: pass DMA-able buffer to spi_nor_read_raw()
Date: Thu, 8 Nov 2018 14:01:35 +0100 [thread overview]
Message-ID: <20181108140135.09a23152@bbrezillon> (raw)
In-Reply-To: <20181108110653.21063-6-tudor.ambarus@microchip.com>
On Thu, 8 Nov 2018 11:07:16 +0000
<Tudor.Ambarus@microchip.com> wrote:
> spi_nor_read_raw() calls nor->read() which might be implemented
> by the m25p80 driver. m25p80 uses the spi-mem layer which requires
> DMA-able in/out buffers. Pass kmalloc'ed dma buffer to spi_nor_read_raw().
>
> Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
> ---
> drivers/mtd/spi-nor/spi-nor.c | 14 ++++++++++----
> 1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> index 79ca1102faed..2eaa21c85483 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c
> @@ -2161,7 +2161,7 @@ spi_nor_set_pp_settings(struct spi_nor_pp_command *pp,
> * @nor: pointer to a 'struct spi_nor'
> * @addr: offset in the serial flash memory
> * @len: number of bytes to read
> - * @buf: buffer where the data is copied into
> + * @buf: buffer where the data is copied into (dma-safe memory)
> *
> * Return: 0 on success, -errno otherwise.
> */
> @@ -2868,11 +2868,16 @@ static const u32 *spi_nor_get_map_in_use(struct spi_nor *nor, const u32 *smpt,
> u8 smpt_len)
> {
> const u32 *ret;
> + u8 *dma_safe;
I'd prefer to have it named buf, data_buf or scratch_buf...
> u32 addr;
> int err;
> u8 i, ncmds, nmaps;
> u8 addr_width, read_opcode, read_dummy;
> - u8 read_data_mask, data_byte, map_id;
> + u8 read_data_mask, map_id;
> +
... and have a comment here explaining why your allocating the buffer
instead of using a local var placed on the stack.
> + dma_safe = kmalloc(sizeof(*dma_safe), GFP_KERNEL | GFP_DMA);
Please don't use GFP_DMA, kmalloc() should already return a DMA-safe
buffer (see [1]).
> + if (!dma_safe)
> + return ERR_PTR(-ENOMEM);
>
> addr_width = nor->addr_width;
> read_dummy = nor->read_dummy;
> @@ -2890,7 +2895,7 @@ static const u32 *spi_nor_get_map_in_use(struct spi_nor *nor, const u32 *smpt,
> nor->read_opcode = SMPT_CMD_OPCODE(smpt[i]);
> addr = smpt[i + 1];
>
> - err = spi_nor_read_raw(nor, addr, 1, &data_byte);
> + err = spi_nor_read_raw(nor, addr, 1, dma_safe);
> if (err) {
> ret = ERR_PTR(err);
> goto out;
> @@ -2900,7 +2905,7 @@ static const u32 *spi_nor_get_map_in_use(struct spi_nor *nor, const u32 *smpt,
> * Build an index value that is used to select the Sector Map
> * Configuration that is currently in use.
> */
> - map_id = map_id << 1 | !!(data_byte & read_data_mask);
> + map_id = map_id << 1 | !!(*dma_safe & read_data_mask);
> ncmds++;
> }
>
> @@ -2941,6 +2946,7 @@ static const u32 *spi_nor_get_map_in_use(struct spi_nor *nor, const u32 *smpt,
>
> /* fall through */
> out:
> + kfree(dma_safe);
> nor->addr_width = addr_width;
> nor->read_dummy = read_dummy;
> nor->read_opcode = read_opcode;
[1]https://elixir.bootlin.com/linux/latest/source/include/linux/gfp.h#L263
next prev parent reply other threads:[~2018-11-08 13:01 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-08 11:07 [PATCH 0/7] mtd: spi-nor: fixes found when debugging smpt Tudor.Ambarus
2018-11-08 11:07 ` [PATCH 1/7] mtd: spi-nor: don't drop sfdp data if optional parsers fail Tudor.Ambarus
2018-11-08 11:07 ` [PATCH 2/7] mtd: spi-nor: fix iteration over smpt array Tudor.Ambarus
2018-11-08 12:50 ` Boris Brezillon
2018-11-08 11:07 ` [PATCH 3/7] mtd: spi-nor: add restriction for nmaps in smpt parser Tudor.Ambarus
2018-11-08 12:54 ` Boris Brezillon
2018-11-08 13:08 ` Boris Brezillon
2018-11-08 13:58 ` Tudor.Ambarus
2018-11-08 14:15 ` Boris Brezillon
2018-11-08 14:48 ` Tudor.Ambarus
2018-11-08 14:54 ` Boris Brezillon
2018-11-08 15:00 ` Tudor.Ambarus
2018-11-08 11:07 ` [PATCH 4/7] mtd: spi-nor: don't overwrite errno in spi_nor_get_map_in_use() Tudor.Ambarus
2018-11-08 11:07 ` [PATCH 5/7] mtd: spi_nor: pass DMA-able buffer to spi_nor_read_raw() Tudor.Ambarus
2018-11-08 13:01 ` Boris Brezillon [this message]
2018-11-08 11:07 ` [PATCH 6/7] mtd: spi-nor: ensure memory used for nor->read() is DMA safe Tudor.Ambarus
2018-11-08 13:03 ` Boris Brezillon
2018-11-08 11:07 ` [PATCH 7/7] mtd: spi-nor: remove unneeded smpt zeroization Tudor.Ambarus
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