On Fri, 27 Apr 2018 16:18:05 +1000
NeilBrown <n...@brown.name> wrote:
> Hi,
> I've labeled this an RFC because I'm really not sure about removing the
> error path from spi_nor_write() -- maybe that really matters. But on
> my hardware, performing multiple small spi writes to the flash seems
> to work.
>
> The spi driver is drivers/staging/mt7621-spi. Possibly this needs to
> use DMA instead of a FIFO (assuming the hardware can) - or maybe
> drivers/spi/spi-mt65xx.c can be made to work on this hardware, though
> that is for an ARM SOC and mt7621 is a MIPS SOC.
>
> I note that openwrt has similar patches:
>
> target/linux/generic/pending-4.14/450-mtd-spi-nor-allow-NOR-driver-to-write-fewer-bytes-th.patch
>
> They also change the spi driver to do a short write, rather
> than change m25p80 to request a short write.
>
> Is there something horribly wrong with this?
Marek, any opinion on this patch?
>
> Thanks,
> NeilBrown
>
> -----------------------8<------------------------
>
> m25p80 honours max_message_size and max_transfer_size
> for reads, but not for writes.
> I have a driver that has a max message size of 36 bytes
> (command, address, 32 bytes data, all places in a FIFO
> in the controller).
> This requires m25p80_write() to honour the size limits.
> For that to work, spi-nor needs to quietly accept partial
> writes.
>
> With this, I can successfully re-flash my device.
>
> Signed-off-by: NeilBrown <n...@brown.name>
> ---
> drivers/mtd/devices/m25p80.c | 3 ++-
> drivers/mtd/spi-nor/spi-nor.c | 7 -------
> 2 files changed, 2 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
> index a4e18f6aaa33..7ded13507604 100644
> --- a/drivers/mtd/devices/m25p80.c
> +++ b/drivers/mtd/devices/m25p80.c
> @@ -117,7 +117,8 @@ static ssize_t m25p80_write(struct spi_nor *nor, loff_t
> to, size_t len,
>
> t[data_idx].tx_buf = buf;
> t[data_idx].tx_nbits = data_nbits;
> - t[data_idx].len = len;
> + t[data_idx].len = min3(len, spi_max_transfer_size(spi),
> + spi_max_message_size(spi) - cmd_sz);
> spi_message_add_tail(&t[data_idx], &m);
>
> ret = spi_sync(spi, &m);
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> index 42ae9a1529bb..cfa15f2801ad 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c
> @@ -1445,13 +1445,6 @@ static int spi_nor_write(struct mtd_info *mtd, loff_t
> to, size_t len,
> goto write_err;
> *retlen += written;
> i += written;
> - if (written != page_remain) {
> - dev_err(nor->dev,
> - "While writing %zu bytes written %zd bytes\n",
> - page_remain, written);
> - ret = -EIO;
> - goto write_err;
> - }
> }
>
> write_err:
