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Thu, 6 May 2021 14:18:50 -0500 Received: from lelv0326.itg.ti.com (10.180.67.84) by DFLE110.ent.ti.com (10.64.6.31) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2 via Frontend Transport; Thu, 6 May 2021 14:18:50 -0500 Received: from pratyush-OptiPlex-790.dhcp.ti.com (ileax41-snat.itg.ti.com [10.172.224.153]) by lelv0326.itg.ti.com (8.15.2/8.15.2) with ESMTP id 146JIUNH026052; Thu, 6 May 2021 14:18:47 -0500 From: Pratyush Yadav To: Tudor Ambarus , Michael Walle , Miquel Raynal , Richard Weinberger , Vignesh Raghavendra , Mark Brown , , , CC: Pratyush Yadav Subject: [PATCH 5/6] mtd: spi-nor: core; avoid odd length/address reads on 8D-8D-8D mode Date: Fri, 7 May 2021 00:48:28 +0530 Message-ID: <20210506191829.8271-6-p.yadav@ti.com> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210506191829.8271-1-p.yadav@ti.com> References: <20210506191829.8271-1-p.yadav@ti.com> MIME-Version: 1.0 X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210506_121854_313595_18A2A5ED X-CRM114-Status: GOOD ( 20.60 ) X-Spam-Score: -2.8 (--) X-Spam-Report: Spam detection software, running on the system "bombadil.infradead.org", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: On Octal DTR capable flashes like Micron Xcella reads cannot start or end at an odd address in Octal DTR mode. Extra bytes need to be read at the start or end to make sure both the start address and l [...] Content analysis details: (-2.8 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at https://www.dnswl.org/, medium trust [198.47.19.141 listed in list.dnswl.org] 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.0 SPF_PASS SPF: sender matches SPF record -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain -0.3 DKIMWL_WL_HIGH DKIMwl.org - High trust sender X-BeenThere: linux-mtd@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-mtd" Errors-To: linux-mtd-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org On Octal DTR capable flashes like Micron Xcella reads cannot start or end at an odd address in Octal DTR mode. Extra bytes need to be read at the start or end to make sure both the start address and length remain even. To avoid allocating too much extra memory, thereby putting unnecessary memory pressure on the system, the temporary buffer containing the extra padding bytes is capped at PAGE_SIZE bytes. The rest of the 2-byte aligned part should be read directly in the main buffer. Signed-off-by: Pratyush Yadav Reviewed-by: Michael Walle --- drivers/mtd/spi-nor/core.c | 81 +++++++++++++++++++++++++++++++++++++- 1 file changed, 80 insertions(+), 1 deletion(-) diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c index 5cc206b8bbf3..3d66cc34af4d 100644 --- a/drivers/mtd/spi-nor/core.c +++ b/drivers/mtd/spi-nor/core.c @@ -1904,6 +1904,82 @@ static const struct flash_info *spi_nor_read_id(struct spi_nor *nor) return ERR_PTR(-ENODEV); } +/* + * On Octal DTR capable flashes like Micron Xcella reads cannot start or + * end at an odd address in Octal DTR mode. Extra bytes need to be read + * at the start or end to make sure both the start address and length + * remain even. + */ +static int spi_nor_octal_dtr_read(struct spi_nor *nor, loff_t from, size_t len, + u_char *buf) +{ + u_char *tmp_buf; + size_t tmp_len; + loff_t start, end; + int ret, bytes_read; + + if (IS_ALIGNED(from, 2) && IS_ALIGNED(len, 2)) + return spi_nor_read_data(nor, from, len, buf); + else if (IS_ALIGNED(from, 2) && len > PAGE_SIZE) + return spi_nor_read_data(nor, from, round_down(len, PAGE_SIZE), + buf); + + tmp_buf = kmalloc(PAGE_SIZE, GFP_KERNEL); + if (!tmp_buf) + return -ENOMEM; + + start = round_down(from, 2); + end = round_up(from + len, 2); + + /* + * Avoid allocating too much memory. The requested read length might be + * quite large. Allocating a buffer just as large (slightly bigger, in + * fact) would put unnecessary memory pressure on the system. + * + * For example if the read is from 3 to 1M, then this will read from 2 + * to 4098. The reads from 4098 to 1M will then not need a temporary + * buffer so they can proceed as normal. + */ + tmp_len = min_t(size_t, end - start, PAGE_SIZE); + + ret = spi_nor_read_data(nor, start, tmp_len, tmp_buf); + if (ret == 0) { + ret = -EIO; + goto out; + } + if (ret < 0) + goto out; + + /* + * More bytes are read than actually requested, but that number can't be + * reported to the calling function or it will confuse its calculations. + * Calculate how many of the _requested_ bytes were read. + */ + bytes_read = ret; + + if (from != start) + ret -= from - start; + + /* + * Only account for extra bytes at the end if they were actually read. + * For example, if the total length was truncated because of temporary + * buffer size limit then the adjustment for the extra bytes at the end + * is not needed. + */ + if (start + bytes_read == end) + ret -= end - (from + len); + + if (ret < 0) { + ret = -EIO; + goto out; + } + + memcpy(buf, tmp_buf + (from - start), ret); +out: + kfree(tmp_buf); + return ret; +} + static int spi_nor_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf) { @@ -1921,7 +1997,10 @@ static int spi_nor_read(struct mtd_info *mtd, loff_t from, size_t len, addr = spi_nor_convert_addr(nor, addr); - ret = spi_nor_read_data(nor, addr, len, buf); + if (nor->read_proto == SNOR_PROTO_8_8_8_DTR) + ret = spi_nor_octal_dtr_read(nor, addr, len, buf); + else + ret = spi_nor_read_data(nor, addr, len, buf); if (ret == 0) { /* We shouldn't see 0-length reads */ ret = -EIO;