[PATCH 5.10 538/545] mtd: rawnand: arasan: Prevent an unsupported configuration

Greg Kroah-Hartman
2022-08-19T16:54:22Z

From: Miquel Raynal <miquel.raynal@bootlin.com>

commit fc9e18f9e987ad46722dad53adab1c12148c213c upstream.

Under the following conditions:
* after rounding up by 4 the number of bytes to transfer (this is
related to the controller's internal constraints),
* if this (rounded) amount of data is situated beyond the end of the
device,
* and only in NV-DDR mode,
the Arasan NAND controller timeouts.

This currently can happen in a particular helper used when picking
software ECC algorithms. Let's prevent this situation by refusing to use
the NV-DDR interface with software engines.

Fixes: 4edde6031458 ("mtd: rawnand: arasan: Support NV-DDR interface")
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20211008163640.1753821-1-miquel.raynal@bootlin.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/mtd/nand/raw/arasan-nand-controller.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)

--- a/drivers/mtd/nand/raw/arasan-nand-controller.c
+++ b/drivers/mtd/nand/raw/arasan-nand-controller.c
@@ -891,6 +891,21 @@ static int anfc_setup_interface(struct n
nvddr = nand_get_nvddr_timings(conf);
if (IS_ERR(nvddr))
return PTR_ERR(nvddr);
+
+ /*
+ * The controller only supports data payload requests which are
+ * a multiple of 4. In practice, most data accesses are 4-byte
+ * aligned and this is not an issue. However, rounding up will
+ * simply be refused by the controller if we reached the end of
+ * the device *and* we are using the NV-DDR interface(!). In
+ * this situation, unaligned data requests ending at the device
+ * boundary will confuse the controller and cannot be performed.
+ *
+ * This is something that happens in nand_read_subpage() when
+ * selecting software ECC support and must be avoided.
+ */
+ if (chip->ecc.engine_type == NAND_ECC_ENGINE_TYPE_SOFT)
+ return -ENOTSUPP;
} else {
sdr = nand_get_sdr_timings(conf);
if (IS_ERR(sdr))