Re: linux 4.2-rc1 broken Nokia N900

[Michael Welling <mwelling@ieee.org>]

On Tue, Jul 14, 2015 at 09:14:12AM +0200, Pali Rohár wrote:
> On Monday 13 July 2015 17:36:07 Michael Welling wrote:
> > On Tue, Jul 14, 2015 at 12:02:44AM +0200, Pali Rohár wrote:
> > > I think nothing special. I just call:
> > > 
> > > export ARCH=arm
> > > export CROSS_COMPILE=arm-linux-gnueabi-
> > > make rx51_defconfig
> > > rm -f arch/arm/boot/zImage
> > > make -j12 zImage modules omap3-n900.dtb CONFIG_DEBUG_SECTION_MISMATCH=y
> > > cat arch/arm/boot/zImage arch/arm/boot/dts/omap3-n900.dtb > arch/arm/boot/zImage.new
> > > mv arch/arm/boot/zImage.new arch/arm/boot/zImage
> > >
> > 
> > Where are you getting rx51_defconfig from?
> > 
> > This does not appear to be in the kernel source any longer.
> > 
> > Can you try the above with omap2plus_defconfig?
> >  
> 
> It is in my linux-n900 repository: https://github.com/pali/linux-n900
> Repository contains more n900 specific patches but SPI code is unpatched
> 
> https://github.com/pali/linux-n900/blob/HEAD/arch/arm/configs/rx51_defconfig
> 
> Later in week I can try to compile also with omap2plus_defconfig...
> But in my opinion kernel should not crash with different configuration.

True.

Could you try the following change to the set_cs function and see if it helps.

diff --git a/drivers/spi/spi-omap2-mcspi.c b/drivers/spi/spi-omap2-mcspi.c
index 5867384..666038b 100644
--- a/drivers/spi/spi-omap2-mcspi.c
+++ b/drivers/spi/spi-omap2-mcspi.c
@@ -245,16 +245,18 @@ static void omap2_mcspi_set_enable(const struct spi_device *spi, int enable)
 
 static void omap2_mcspi_set_cs(struct spi_device *spi, bool enable)
 {
+	struct omap2_mcspi_cs *cs = spi->controller_state;
 	u32 l;
 
-	/* The controller handles the inverted chip selects
-	 * using the OMAP2_MCSPI_CHCONF_EPOL bit so revert
-	 * the inversion from the core spi_set_cs function.
-	 */
-	if (spi->mode & SPI_CS_HIGH)
-		enable = !enable;
+	if (cs) {
+
+		/* The controller handles the inverted chip selects
+		 * using the OMAP2_MCSPI_CHCONF_EPOL bit so revert
+		 * the inversion from the core spi_set_cs function.
+		 */
+		if (spi->mode & SPI_CS_HIGH)
+			enable = !enable;
 
-	if (spi->controller_state) {
 		l = mcspi_cached_chconf0(spi);
 
 		if (enable)