mtd: rawnand: Clarify conditions to enable continuous reads

commit 828f6df1bcba7f64729166efc7086ea657070445 upstream.

The current logic is probably fine but is a bit convoluted. Plus, we
don't want partial pages to be part of the sequential operation just in
case the core would optimize the page read with a subpage read (which
would break the sequence). This may happen on the first and last page
only, so if the start offset or the end offset is not aligned with a
page boundary, better avoid them to prevent any risk.

Cc: stable@vger.kernel.org
Fixes: 003fe4b9545b ("mtd: rawnand: Support for sequential cache reads")
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Tested-by: Martin Hundebøll <martin@geanix.com>
Link: https://lore.kernel.org/linux-mtd/20231215123208.516590-5-miquel.raynal@bootlin.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index 7610619..76167b8 100644 (file)
--- a/drivers/mtd/nand/raw/nand_base.c
+++ b/drivers/mtd/nand/raw/nand_base.c
@@ -3461,21 +3461,29 @@ static void rawnand_enable_cont_reads(struct nand_chip *chip, unsigned int page,
                                      u32 readlen, int col)
 {
        struct mtd_info *mtd = nand_to_mtd(chip);
+       unsigned int end_page, end_col;
+
+       chip->cont_read.ongoing = false;
 
        if (!chip->controller->supported_op.cont_read)
                return;
 
-       if ((col && col + readlen < (3 * mtd->writesize)) ||
-           (!col && readlen < (2 * mtd->writesize))) {
-               chip->cont_read.ongoing = false;
+       end_page = DIV_ROUND_UP(col + readlen, mtd->writesize);
+       end_col = (col + readlen) % mtd->writesize;
+
+       if (col)
+               page++;
+
+       if (end_col && end_page)
+               end_page--;
+
+       if (page + 1 > end_page)
                return;
-       }
 
-       chip->cont_read.ongoing = true;
        chip->cont_read.first_page = page;
-       if (col)
-               chip->cont_read.first_page++;
-       chip->cont_read.last_page = page + ((readlen >> chip->page_shift) & chip->pagemask);
+       chip->cont_read.last_page = end_page;
+       chip->cont_read.ongoing = true;
+
        rawnand_cap_cont_reads(chip);
 }