spi: core: Ignore unsupported Dual/Quad Transfer Mode bits

commit 83596fbeb5d28e8cb8878786133945d4dc7c0090 upstream.

The availability of SPI Dual or Quad Transfer Mode as indicated by the
"spi-tx-bus-width" and "spi-rx-bus-width" properties in the device tree is
a hardware property of the SPI master, SPI slave, and board wiring.  Hence
the SPI core should not reject an SPI slave because an SPI master driver
doesn't (yet) support Dual or Quad Transfer Mode.

Change the lack of Dual or Quad Transfer Mode support in the SPI master
driver from an error condition to a warning condition, and ignore the
unsupported mode bits, falling back to Single Transfer Mode, to avoid
breakages when running old kernels with new device trees.

Fixes: f477b7fb13df (spi: DUAL and QUAD support)
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Mark Brown <broonie@linaro.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 9e039c60c0680ae761e2be41f0de0a171368f3c6..d254477372b9e7c959ce700ae143ae580efab5a8 100644 (file)
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1370,7 +1370,7 @@ EXPORT_SYMBOL_GPL(spi_busnum_to_master);
  */
 int spi_setup(struct spi_device *spi)
 {
-       unsigned        bad_bits;
+       unsigned        bad_bits, ugly_bits;
        int             status = 0;
 
        /* check mode to prevent that DUAL and QUAD set at the same time
@@ -1390,6 +1390,15 @@ int spi_setup(struct spi_device *spi)
         * that aren't supported with their current master
         */
        bad_bits = spi->mode & ~spi->master->mode_bits;
+       ugly_bits = bad_bits &
+                   (SPI_TX_DUAL | SPI_TX_QUAD | SPI_RX_DUAL | SPI_RX_QUAD);
+       if (ugly_bits) {
+               dev_warn(&spi->dev,
+                        "setup: ignoring unsupported mode bits %x\n",
+                        ugly_bits);
+               spi->mode &= ~ugly_bits;
+               bad_bits &= ~ugly_bits;
+       }
        if (bad_bits) {
                dev_err(&spi->dev, "setup: unsupported mode bits %x\n",
                        bad_bits);