From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx2.suse.de ([195.135.220.15]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1fBwiF-0001mJ-CY for linux-mtd@lists.infradead.org; Fri, 27 Apr 2018 06:18:36 +0000 From: NeilBrown To: David Woodhouse , Brian Norris , Boris Brezillon , Marek Vasut , Richard Weinberger Date: Fri, 27 Apr 2018 16:18:05 +1000 Subject: [PATCH/RFC] mtd: spi-nor: honour max_message_size for spi-nor writes. cc: linux-mtd@lists.infradead.org , linux-kernel@vger.kernel.org Message-ID: <87efj1kw9u.fsf@notabene.neil.brown.name> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha256; protocol="application/pgp-signature" List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , --=-=-= Content-Type: text/plain Content-Transfer-Encoding: quoted-printable 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-wri= te-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 =2D----------------------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 =2D-- 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 =2D-- 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, =20 t[data_idx].tx_buf =3D buf; t[data_idx].tx_nbits =3D data_nbits; =2D t[data_idx].len =3D len; + t[data_idx].len =3D min3(len, spi_max_transfer_size(spi), + spi_max_message_size(spi) - cmd_sz); spi_message_add_tail(&t[data_idx], &m); =20 ret =3D 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 =2D-- 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 +=3D written; i +=3D written; =2D if (written !=3D page_remain) { =2D dev_err(nor->dev, =2D "While writing %zu bytes written %zd bytes\n", =2D page_remain, written); =2D ret =3D -EIO; =2D goto write_err; =2D } } =20 write_err: =2D-=20 2.14.0.rc0.dirty --=-=-= Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEG8Yp69OQ2HB7X0l6Oeye3VZigbkFAlriwJ4ACgkQOeye3VZi gbmRwBAAwi4AdVg4ovvqDLYTp/CuEgtnrWESRutah65+tJ54Gvn1pRWfmuUC2WuT DSwHd/l4QtvVGMUvfD/2j5mHjfdLrqfDLWok9Q1mMDH0mg8tYHOshHvpXlB0bj7T SpQ1RQQoQnLJKg6y5tvvTr5DK/PRKUZaF5Yule7JknSxVeRFsnnuB9AdzbCH1Hzz 7iJH3Tgu4g2YzsaXRRwaI1+rMSGZEGSwsGXX3g6zXY9aSEaipK42t2gfnQ5r8Ysu HBHOVGY8v2/A+iD5NgOGeZ4LUjznYHQNPlj7+T+zG3fqYKqKYNgw/Lwjl09c1QjW mBTn7+DD/p/p8gLy/4uB2RLAMbunCAWBFqCL+AnSQ9A7mK5s9N0VjkRcvYYJvygM WO2qqMQ1i7q9m8fC33gW085Nl12AtcZqctYscqtc+OrBDyrp+GE41PFpnTR5p0Oz kBbnkYF8flY+zX81W7XwnKkOaeOfvESlagSOTCLs5n75Hrpr1Ve50pUuD3tyPqNU VyL8BcvkzYBAf7drKVTz+pnlTur52+eWCvGA+IeRE/WJUSh4hSZ3nI/reAsC7Hoh DowFOpi3+YenTskDsmIp+hzLY1sxbn06lHaDnMz5i40fWX4iRHTikjkNceN+oXzR TOkZ7T6Pf9mMyiY1rclRzNiEXI0kcHddOpYpFHQUwH+Dbtwmwn0= =XTh7 -----END PGP SIGNATURE----- --=-=-=--