From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752230AbcGAWYg (ORCPT ); Fri, 1 Jul 2016 18:24:36 -0400 Received: from mail-pf0-f193.google.com ([209.85.192.193]:35129 "EHLO mail-pf0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750803AbcGAWYe (ORCPT ); Fri, 1 Jul 2016 18:24:34 -0400 From: Brian Norris To: Cc: , Brian Norris , Marek Vasut , =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= , Ezequiel Garcia , Julius Werner Subject: [PATCH] mtd: spi-nor: perform read-back check after SR lock/unlock Date: Fri, 1 Jul 2016 15:23:16 -0700 Message-Id: <1467411796-110267-1-git-send-email-computersforpeace@gmail.com> X-Mailer: git-send-email 2.8.0.rc3.226.g39d4020 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When programming the Status Register for performing write protect, it's important to know the result of the operation (i.e., success or failure). Particularly, it's possible to fail when the hardware write protect pin (WP#) is asserted, potentially disallowing writes to the status register. Previously, even if we weren't able to update the status register, ioctl(MEMLOCK) and ioctl(MEMUNLOCK) would return success. Let's add a read-back check, to make sure that the status register was updated appropriately. If the relevant bits weren't updated, then return -EIO. Signed-off-by: Brian Norris --- drivers/mtd/spi-nor/spi-nor.c | 52 ++++++++++++++++++++++++++++++++++++++----- 1 file changed, 46 insertions(+), 6 deletions(-) diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c index 14cf6ac8c0a5..9551e41699c8 100644 --- a/drivers/mtd/spi-nor/spi-nor.c +++ b/drivers/mtd/spi-nor/spi-nor.c @@ -519,12 +519,18 @@ static int stm_lock(struct spi_nor *nor, loff_t ofs, uint64_t len) struct mtd_info *mtd = &nor->mtd; int status_old, status_new; u8 mask = SR_BP2 | SR_BP1 | SR_BP0; + u8 wr_mask = mask; u8 shift = ffs(mask) - 1, pow, val; loff_t lock_len; - bool can_be_top = true, can_be_bottom = nor->flags & SNOR_F_HAS_SR_TB; + bool can_be_top = true, can_be_bottom = false; bool use_top; int ret; + if (nor->flags & SNOR_F_HAS_SR_TB) { + wr_mask |= SR_TB; + can_be_bottom = true; + } + status_old = read_sr(nor); if (status_old < 0) return status_old; @@ -571,7 +577,7 @@ static int stm_lock(struct spi_nor *nor, loff_t ofs, uint64_t len) if (!(val & mask)) return -EINVAL; - status_new = (status_old & ~mask & ~SR_TB) | val; + status_new = (status_old & ~wr_mask) | val; /* Disallow further writes if WP pin is asserted */ status_new |= SR_SRWD; @@ -591,7 +597,21 @@ static int stm_lock(struct spi_nor *nor, loff_t ofs, uint64_t len) ret = write_sr(nor, status_new); if (ret) return ret; - return spi_nor_wait_till_ready(nor); + ret = spi_nor_wait_till_ready(nor); + if (ret) + return ret; + + ret = read_sr(nor); + if (ret < 0) + return ret; + + if ((ret ^ status_new) & (wr_mask | SR_SRWD)) { + dev_dbg(nor->dev, "read-back failure: %#x, %#x\n", + status_new, ret); + return -EIO; + } + + return 0; } /* @@ -604,12 +624,18 @@ static int stm_unlock(struct spi_nor *nor, loff_t ofs, uint64_t len) struct mtd_info *mtd = &nor->mtd; int status_old, status_new; u8 mask = SR_BP2 | SR_BP1 | SR_BP0; + u8 wr_mask = mask; u8 shift = ffs(mask) - 1, pow, val; loff_t lock_len; - bool can_be_top = true, can_be_bottom = nor->flags & SNOR_F_HAS_SR_TB; + bool can_be_top = true, can_be_bottom = false; bool use_top; int ret; + if (nor->flags & SNOR_F_HAS_SR_TB) { + wr_mask |= SR_TB; + can_be_bottom = true; + } + status_old = read_sr(nor); if (status_old < 0) return status_old; @@ -658,7 +684,7 @@ static int stm_unlock(struct spi_nor *nor, loff_t ofs, uint64_t len) return -EINVAL; } - status_new = (status_old & ~mask & ~SR_TB) | val; + status_new = (status_old & ~wr_mask) | val; /* Don't protect status register if we're fully unlocked */ if (lock_len == 0) @@ -679,7 +705,21 @@ static int stm_unlock(struct spi_nor *nor, loff_t ofs, uint64_t len) ret = write_sr(nor, status_new); if (ret) return ret; - return spi_nor_wait_till_ready(nor); + ret = spi_nor_wait_till_ready(nor); + if (ret) + return ret; + + ret = read_sr(nor); + if (ret < 0) + return ret; + + if ((ret ^ status_new) & (wr_mask | SR_SRWD)) { + dev_dbg(nor->dev, "read-back failure: %#x, %#x\n", + status_new, ret); + return -EIO; + } + + return 0; } /* -- 2.8.0.rc3.226.g39d4020