On 08/01/2019 07:22 PM, Vignesh Raghavendra wrote:
> External E-Mail
>
>
> spi-mem layer expects all buffers passed to it to be DMA'able. But
> spi-nor layer mostly allocates buffers on stack for reading/writing to
> registers and therefore are not DMA'able. Introduce bounce buffer to be
> used to read/write to registers. This ensures that buffer passed to
> spi-mem layer during register read/writes is DMA'able. With this change
> nor->cmd-buf is no longer used, so drop it.
>
> Reviewed-by: Boris Brezillon <[email protected]>
> Signed-off-by: Vignesh Raghavendra <[email protected]>
> ---
>
> v4:
> Avoid memcpy during READID
>
> v3: new patch
>
> drivers/mtd/spi-nor/spi-nor.c | 70 ++++++++++++++++++++---------------
> include/linux/mtd/spi-nor.h | 7 +++-
> 2 files changed, 45 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> index 03cc788511d5..e02376e1127b 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c
cut
> /**
> @@ -1404,9 +1401,11 @@ static int write_sr_cr(struct spi_nor *nor, u8 *sr_cr)
> {
> int ret;
>
> + memcpy(nor->bouncebuf, sr_cr, 2);
I'm thinking out loud. This can be avoided by forcing all the callers to use
nor->bouncebuf. That would result in a:
static int write_sr(struct spi_nor *nor, size_t len)
write_sr_cr() can be removed. Memcopying 2 bytes is a small price to pay, we can
keep things as they are, to not be too invasive. But if you think that this idea
is worth it, tell.
> +
> write_enable(nor);
>
> - ret = nor->write_reg(nor, SPINOR_OP_WRSR, sr_cr, 2);
> + ret = nor->write_reg(nor, SPINOR_OP_WRSR, nor->bouncebuf, 2);
> if (ret < 0) {
> dev_err(nor->dev,
> "error while writing configuration register\n");
cut
> @@ -2177,9 +2176,10 @@ static const struct flash_info spi_nor_ids[] = {
> static const struct flash_info *spi_nor_read_id(struct spi_nor *nor)
> {
> int tmp;
> - u8 id[SPI_NOR_MAX_ID_LEN];
> + u8 *id;
> const struct flash_info *info;
>
> + id = nor->bouncebuf;
nit: do init at declaration.
Also, you missed a place in which you can use the bouncebuf, search by
"read_reg(":
ret = nor->read_reg(nor, SPINOR_OP_XRDSR, &val, 1);
Cheers,
ta
