[3.13.y.z extended stable] Patch "spi: core: Ignore unsupported Dual/Quad Transfer Mode bits" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

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

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.4.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 1735c34b5ad5989a1b550abd99bac7ba444d67b6 Mon Sep 17 00:00:00 2001
From: Geert Uytterhoeven <geert+renesas at glider.be>
Date: Mon, 14 Apr 2014 19:39:53 +0200
Subject: 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 at glider.be>
Signed-off-by: Mark Brown <broonie at linaro.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/spi/spi.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 349ebba..a416aec 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1551,7 +1551,7 @@ 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
@@ -1571,6 +1571,15 @@ 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);
--
1.9.1