From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mga09.intel.com ([134.134.136.24]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1g0lgA-0006QM-WC for linux-mtd@lists.infradead.org; Fri, 14 Sep 2018 10:50:28 +0000 From: Jarkko Nikula To: linux-mtd@lists.infradead.org Cc: Marek Vasut , David Woodhouse , Brian Norris , Boris Brezillon , Richard Weinberger , Jarkko Nikula Subject: [PATCH] mtd: spi-nor: Use DMA-safe buffer for JEDEC ID in spi_nor_read_id() Date: Fri, 14 Sep 2018 13:49:01 +0300 Message-Id: <20180914104901.4480-1-jarkko.nikula@linux.intel.com> List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , After commit 4120f8d158ef ("mtd: spi-nor: Use the spi_mem_xx() API") there is no allocation for DMA-safe buffer when transmitting data bytes over SPI bus in m25p80 driver. JEDEC ID reading in spi_nor_read_id() has the buffer in stack. This is not safe with the m25p80 driver anymore after commit 4120f8d158ef if underlying SPI controller is using DMA for transfers. Therefore allocate a temporary DMA-safe buffer for JEDEC ID reading. Signed-off-by: Jarkko Nikula --- I'm not an spi-nor expert at all but noticed this "WARNING: CPU: 3 PID: 154 at kernel/dma/debug.c:1191 check_for_stack+0xc2/0x1a0" after 4120f8d158ef since my test setup has DMA debugging enabled and using DMA for SPI. I don't know are there other places that may transfer from stack but it looked potentially better to have the buffer allocated in spi_nor_read_id() instead of doing allocation & copy all the places that 4120f8d158ef touches. --- drivers/mtd/spi-nor/spi-nor.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c index f028277fb1ce..f2294ed14d8f 100644 --- a/drivers/mtd/spi-nor/spi-nor.c +++ b/drivers/mtd/spi-nor/spi-nor.c @@ -1269,25 +1269,37 @@ 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]; - const struct flash_info *info; + u8 *id; + const struct flash_info *info, *ret; + + id = kzalloc(SPI_NOR_MAX_ID_LEN, GFP_KERNEL | GFP_DMA); + if (!id) { + ret = ERR_PTR(ENOMEM); + goto out; + } tmp = nor->read_reg(nor, SPINOR_OP_RDID, id, SPI_NOR_MAX_ID_LEN); if (tmp < 0) { dev_dbg(nor->dev, "error %d reading JEDEC ID\n", tmp); - return ERR_PTR(tmp); + ret = ERR_PTR(tmp); + goto out; } for (tmp = 0; tmp < ARRAY_SIZE(spi_nor_ids) - 1; tmp++) { info = &spi_nor_ids[tmp]; if (info->id_len) { - if (!memcmp(info->id, id, info->id_len)) - return &spi_nor_ids[tmp]; + if (!memcmp(info->id, id, info->id_len)) { + ret = &spi_nor_ids[tmp]; + goto out; + } } } dev_err(nor->dev, "unrecognized JEDEC id bytes: %02x, %02x, %02x\n", id[0], id[1], id[2]); - return ERR_PTR(-ENODEV); + ret = ERR_PTR(-ENODEV); +out: + kfree(id); + return ret; } static int spi_nor_read(struct mtd_info *mtd, loff_t from, size_t len, -- 2.18.0