spi: cadence-quadspi: fix incorrect supports_op() return value

Since the conversion to spi-mem, the driver advertised support for
various operations that cqspi_set_protocol() was never expected to handle
correctly - in particuar all non-DTR operations with command or address
buswidth > 1. For DTR, all operations except for 8-8-8 would fail, as
cqspi_set_protocol() returns -EINVAL.

In non-DTR mode, this resulted in data corruption for SPI-NOR flashes that
support such operations. As a minimal fix that can be backported to stable
kernels, simply disallow the unsupported operations again to avoid this
issue.

Fixes: a314f6367787 ("mtd: spi-nor: Convert cadence-quadspi to use spi-mem framework")
Signed-off-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
Link: https://lore.kernel.org/r/20220406132832.199777-1-matthias.schiffer@ew.tq-group.com
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/spi/spi-cadence-quadspi.c b/drivers/spi/spi-cadence-quadspi.c
index 616ada891974e317dce7d992e11eea5cfbfc9ad2..19686fb47bb352727fc9f2038403dd300909469a 100644 (file)
--- a/drivers/spi/spi-cadence-quadspi.c
+++ b/drivers/spi/spi-cadence-quadspi.c
@@ -1415,9 +1415,24 @@ static bool cqspi_supports_mem_op(struct spi_mem *mem,
        all_false = !op->cmd.dtr && !op->addr.dtr && !op->dummy.dtr &&
                    !op->data.dtr;
 
-       /* Mixed DTR modes not supported. */
-       if (!(all_true || all_false))
+       if (all_true) {
+               /* Right now we only support 8-8-8 DTR mode. */
+               if (op->cmd.nbytes && op->cmd.buswidth != 8)
+                       return false;
+               if (op->addr.nbytes && op->addr.buswidth != 8)
+                       return false;
+               if (op->data.nbytes && op->data.buswidth != 8)
+                       return false;
+       } else if (all_false) {
+               /* Only 1-1-X ops are supported without DTR */
+               if (op->cmd.nbytes && op->cmd.buswidth > 1)
+                       return false;
+               if (op->addr.nbytes && op->addr.buswidth > 1)
+                       return false;
+       } else {
+               /* Mixed DTR modes are not supported. */
                return false;
+       }
 
        return spi_mem_default_supports_op(mem, op);
 }