From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm0-x233.google.com ([2a00:1450:400c:c09::233]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1aLXnf-0000JO-Gb for linux-mtd@lists.infradead.org; Tue, 19 Jan 2016 15:02:28 +0000 Received: by mail-wm0-x233.google.com with SMTP id 123so95112278wmz.0 for ; Tue, 19 Jan 2016 07:02:06 -0800 (PST) From: adamsomerville@gmail.com To: David Woodhouse , Brian Norris Cc: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= , Gabor Juhos , Boris Brezillon , Jagan Teki , Mika Westerberg , Furquan Shaikh , linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org, Adam Somerville Subject: [RFC] spi-nor: fix cross die reads on Micron multi-die devices Date: Tue, 19 Jan 2016 15:01:50 +0000 Message-Id: <1453215710-10803-1-git-send-email-adamsomerville@gmail.com> List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Adam Somerville So as far as I can see there is a bug in the spi-nor driver when issuing die boundary crossing reads on Micron multi-die devices. Micron N25Q512A, N25Q00AA and probably any other Micron multi-die devices do not support a single read request that crosses a die boundary. The current behaviour is that the address on the device wraps back to the start of the first die, with any data returned beyond the boundary being from the start of the first die. To reproduce run: (assuming mtd0 is at offset 0 and spans across die boundary) mtd_debug read /dev/mtd0 0x1FFFFF0 32 bad and compare to: mtd_debug read /dev/mtd0 0x1FFFFF0 16 good1 mtd_debug read /dev/mtd0 0x2000000 16 good2 Instead we should split the read request in to 1 read per die. Tested on Cyclone 5 SOC with cadence-qspi connected to Micron n25q512ax3 Signed-off-by: Adam Somerville --- drivers/mtd/spi-nor/spi-nor.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c index ed0c19c..68dc20e 100644 --- a/drivers/mtd/spi-nor/spi-nor.c +++ b/drivers/mtd/spi-nor/spi-nor.c @@ -903,10 +903,19 @@ static const struct flash_info *spi_nor_read_id(struct spi_nor *nor) return ERR_PTR(-ENODEV); } +/* + * Micron multi-die devices do not support cross die boundary + * reads. Split the read request in to 1 read per die + */ +#define MIN_READ_BOUNDARY 0x2000000 +#define DIST_TO_BOUNDARY(x) \ + (MIN_READ_BOUNDARY - ((u32)x & (MIN_READ_BOUNDARY - 1))) + static int spi_nor_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf) { struct spi_nor *nor = mtd_to_spi_nor(mtd); + size_t read_len; int ret; dev_dbg(nor->dev, "from 0x%08x, len %zd\n", (u32)from, len); @@ -915,7 +924,17 @@ static int spi_nor_read(struct mtd_info *mtd, loff_t from, size_t len, if (ret) return ret; - ret = nor->read(nor, from, len, retlen, buf); + do { + read_len = min(len, DIST_TO_BOUNDARY(from)); + + ret = nor->read(nor, from, read_len, retlen, buf); + if (ret) + break; + + from += read_len; + buf += read_len; + len -= read_len; + } while (len > 0); spi_nor_unlock_and_unprep(nor, SPI_NOR_OPS_READ); return ret; -- 1.7.9.5