mtd: rawnand: arasan: Fix double assertion of chip-select

When two chip-selects are configured in the device tree, and the second is
a non-native GPIO, both the GPIO-based chip-select and the first native
chip-select may be asserted simultaneously. This double assertion causes
incorrect read and write operations.

The issue occurs because when nfc->ncs <= 2, nfc->spare_cs is always
initialized to 0 due to static initialization. Consequently, when the
second chip-select (GPIO-based) is selected in anfc_assert_cs(), it is
detected by anfc_is_gpio_cs(), and nfc->native_cs is assigned the value 0.
This results in both the GPIO-based chip-select being asserted and the
NAND controller register receiving 0, erroneously selecting the native
chip-select.

This patch resolves the issue, as confirmed by oscilloscope testing with
configurations involving two or more chip-selects in the device tree.

Fixes: acbd3d0 ("mtd: rawnand: arasan: Leverage additional GPIO CS")
Cc: [email protected]
Signed-off-by: Maciej Andrzejewski <[email protected]>
Signed-off-by: Miquel Raynal <[email protected]>

Author: mandrzejewski-iceye

drivers/mtd/nand/raw/arasan-nand-controller.c

@@ -1409,8 +1409,8 @@ static int anfc_parse_cs(struct arasan_nfc *nfc)
 	 * case, the "not" chosen CS is assigned to nfc->spare_cs and selected
 	 * whenever a GPIO CS must be asserted.
 	 */
-	if (nfc->cs_array && nfc->ncs > 2) {
-		if (!nfc->cs_array[0] && !nfc->cs_array[1]) {
+	if (nfc->cs_array) {
+		if (nfc->ncs > 2 && !nfc->cs_array[0] && !nfc->cs_array[1]) {
 			dev_err(nfc->dev,
 				"Assign a single native CS when using GPIOs\n");
 			return -EINVAL;