Messages in this thread Patch in this message | | | From | NeilBrown <> | Date | Fri, 27 Apr 2018 16:18:05 +1000 | Subject | [PATCH/RFC] mtd: spi-nor: honour max_message_size for spi-nor writes. |
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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?
Thanks, NeilBrown
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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 <neil@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: -- 2.14.0.rc0.dirty [unhandled content-type:application/pgp-signature]
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