linux-kernel - [PATCH] mtd: map_ram: prevent use of point and unpoint when NO

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Message-Id: <20230919113320.16953-1-shivamurthy.shastri@linutronix.de>
Date:   Tue, 19 Sep 2023 13:33:20 +0200
From:   Shivamurthy Shastri <shivamurthy.shastri@...utronix.de>
To:     miquel.raynal@...tlin.com, richard@....at, vigneshr@...com,
        linux-mtd@...ts.infradead.org
Cc:     linus.walleij@...aro.org, b.spranger@...utronix.de,
        shivamurthy.shastri@...utronix.de, linux-kernel@...r.kernel.org
Subject: [PATCH] mtd: map_ram: prevent use of point and unpoint when NO_XIP is set

When the DT property no-unaligned-direct-access is set, map->phys is set
to NO_XIP. With this property set, the flash should not be exposed
directly to MTD users, since it cannot be mapped.

map_ram() exposes the flash direct access unconditionally which leads to
access errors (when the bus width does not match the RAM width).

Therefore do not set point and unpoint when NO_XIP is set.

Signed-off-by: Shivamurthy Shastri <shivamurthy.shastri@...utronix.de>
Reviewed-by: Benedikt Spranger <b.spranger@...utronix.de>
---
 drivers/mtd/chips/map_ram.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/chips/map_ram.c b/drivers/mtd/chips/map_ram.c
index e8dd6496927e..f9d3e32ef8e9 100644
--- a/drivers/mtd/chips/map_ram.c
+++ b/drivers/mtd/chips/map_ram.c
@@ -70,12 +70,16 @@ static struct mtd_info *map_ram_probe(struct map_info *map)
 	mtd->_read = mapram_read;
 	mtd->_write = mapram_write;
 	mtd->_panic_write = mapram_write;
-	mtd->_point = mapram_point;
 	mtd->_sync = mapram_nop;
-	mtd->_unpoint = mapram_unpoint;
 	mtd->flags = MTD_CAP_RAM;
 	mtd->writesize = 1;
 
+	/* Disable direct access when NO_XIP is set */
+	if (map->phys != NO_XIP) {
+		mtd->_point = mapram_point;
+		mtd->_unpoint = mapram_unpoint;
+	}
+
 	mtd->erasesize = PAGE_SIZE;
  	while(mtd->size & (mtd->erasesize - 1))
 		mtd->erasesize >>= 1;
-- 
2.34.1