Merge tag 'spi-nor/for-6.18' into mtd/next

SPI NOR changes for 6.18

Notable changes:

- Some flashes can't perform reads or writes with start or end being an
odd number in Octal DTR mode. File systems like UBIFS can request such
reads or writes, causing the transaction to error out. Pad the read or
write transactions with extra bytes to avoid this problem.

Signed-off-by: Miquel Raynal <[e-mail]>

drivers/mtd/spi-nor/core.c

···
 	return info;
 }
 
+/*
+ * On Octal DTR capable flashes, 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);
+
+	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)
 {
···
 	while (len) {
 		loff_t addr = from;
 
-		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;
···
 read_err:
 	spi_nor_unlock_and_unprep_rd(nor, from_lock, len_lock);
 
+	return ret;
+}
+
+/*
+ * On Octal DTR capable flashes, writes cannot start or end at an odd address
+ * in Octal DTR mode. Extra 0xff bytes need to be appended or prepended to
+ * make sure the start address and end address are even. 0xff is used because
+ * on NOR flashes a program operation can only flip bits from 1 to 0, not the
+ * other way round. 0 to 1 flip needs to happen via erases.
+ */
+static int spi_nor_octal_dtr_write(struct spi_nor *nor, loff_t to, size_t len,
+				   const u8 *buf)
+{
+	u8 *tmp_buf;
+	size_t bytes_written;
+	loff_t start, end;
+	int ret;
+
+	if (IS_ALIGNED(to, 2) && IS_ALIGNED(len, 2))
+		return spi_nor_write_data(nor, to, len, buf);
+
+	tmp_buf = kmalloc(nor->params->page_size, GFP_KERNEL);
+	if (!tmp_buf)
+		return -ENOMEM;
+
+	memset(tmp_buf, 0xff, nor->params->page_size);
+
+	start = round_down(to, 2);
+	end = round_up(to + len, 2);
+
+	memcpy(tmp_buf + (to - start), buf, len);
+
+	ret = spi_nor_write_data(nor, start, end - start, tmp_buf);
+	if (ret == 0) {
+		ret = -EIO;
+		goto out;
+	}
+	if (ret < 0)
+		goto out;
+
+	/*
+	 * More bytes are written 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
+	 * written.
+	 */
+	bytes_written = ret;
+
+	if (to != start)
+		ret -= to - start;
+
+	/*
+	 * Only account for extra bytes at the end if they were actually
+	 * written. For example, if for some reason the controller could only
+	 * complete a partial write then the adjustment for the extra bytes at
+	 * the end is not needed.
+	 */
+	if (start + bytes_written == end)
+		ret -= end - (to + len);
+
+out:
+	kfree(tmp_buf);
 	return ret;
 }
 
···
 			goto write_err;
 		}
 
-		ret = spi_nor_write_data(nor, addr, page_remain, buf + i);
+		if (nor->write_proto == SNOR_PROTO_8_8_8_DTR)
+			ret = spi_nor_octal_dtr_write(nor, addr, page_remain,
+						      buf + i);
+		else
+			ret = spi_nor_write_data(nor, addr, page_remain,
+						 buf + i);
 		spi_nor_unlock_device(nor);
 		if (ret < 0)
 			goto write_err;