Re: [PATCH 0/4] Fix backlight on Armadillo 800 EVA

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Simon,

On Tuesday 17 December 2013 09:56:30 Simon Horman wrote:
> On Tue, Dec 17, 2013 at 09:20:04AM +0900, Simon Horman wrote:
> > On Mon, Dec 16, 2013 at 04:43:39PM +0100, Laurent Pinchart wrote:
> > > On Monday 16 December 2013 11:22:04 Simon Horman wrote:
> > > > On Wed, Dec 11, 2013 at 03:48:14AM +0100, Laurent Pinchart wrote:
> > > > > Hello,
> > > > > 
> > > > > Commit 22ceeee16eb8f0d04de3ef43a5174fb30ec18af9 ("pwm-backlight: Add
> > > > > power supply support") added a mandatory power supply for the PWM
> > > > > backlight, resulting in broken backlight on the Armadillo board.
> > > > > This patch set fixes the issue by adding power supplies to board
> > > > > code and DT, and adds proper handling of the panel enable signal
> > > > > through the PWM backlight enable GPIO.
> > > > > 
> > > > > Patch 1/4 fixes a v3.13 regression. Strictly speaking patch 3/4 is
> > > > > as well, but the backlight was broken anyway with DT due to the
> > > > > enable GPIO not being handled at all, so there's no need to push it
> > > > > to v3.13.
> > > > > 
> > > > > Laurent Pinchart (4):
> > > > >   ARM: shmobile: armadillo: Add PWM backlight power supply
> > > > >   ARM: shmobile: armadillo: Set backlight enable GPIO
> > > > >   ARM: shmobile: armadillo: dts: Add PWM backlight power supply
> > > > >   ARM: shmobile: armadillo: dts: Add PWM backlight enable GPIO
> > > > >  
> > > > >  arch/arm/boot/dts/r8a7740-armadillo800eva-reference.dts | 11 ++++++
> > > > >  arch/arm/mach-shmobile/board-armadillo800eva.c          | 12 ++++--
> > > > >  2 files changed, 19 insertions(+), 4 deletions(-)
> > > > 
> > > > Hi Laurent,
> > > > 
> > > > I am wondering if you could let me know how you exercised this.
> > > > I am not having much luck using /dev/fb/0.
> > > > 
> > > > I have your patches applied on top of
> > > > renesas-devel-v3.13-rc3-20131214v2
> > > > 
> > > > Using Legacy-C I see the following:
> > > > dmesg | grep fb
> > > > sh_mobile_lcdc_fb sh_mobile_lcdc_fb.0: Coherent DMA mask
> > > > 0xffffffffffffffff is larger than dma_addr_t allows sh_mobile_lcdc_fb
> > > > sh_mobile_lcdc_fb.0: Driver did not use or check the return value from
> > > > dma_set_coherent_mask()?
> > > > sh_mobile_lcdc_fb sh_mobile_lcdc_fb.0: unable to allocate buffer
> > > > sh_mobile_lcdc_fb: probe of sh_mobile_lcdc_fb.0 failed with error -12
> > > > sh_mobile_lcdc_fb sh_mobile_lcdc_fb.1: Coherent DMA mask
> > > > 0xffffffffffffffff is larger than dma_addr_t allows sh_mobile_lcdc_fb
> > > > sh_mobile_lcdc_fb.1: Driver did not use or check the return value from
> > > > dma_set_coherent_mask()?
> > > > sh_mobile_lcdc_fb sh_mobile_lcdc_fb.1: unable to allocate buffer
> > > > sh_mobile_lcdc_fb: probe of sh_mobile_lcdc_fb.1 failed with error -12
> > > > 
> > > > And no fb devices in /dev
> > > > 
> > > > I am using armadillo800eva_defconfig
> > > 
> > > I've tried that and got the same error. My kernel config has
> > > CONFIG_SHMOBILE_IOMMU enabled which seems to hide the problem. I'll come
> > > up with a patch to get LCDC working without IOMMU.
> > 
> > Thanks.
> 
> I have applied "[PATCH 1/3] ARM: shmobile: armadillo: Fix coherent DMA
> mask" and the problems I reported above seem to have been resolved, thanks.
> 
> Unfortunately my test of LCDC still seems to fail, so perhaps I need a
> different test.
> 
> My test is as follows:
> 
> bmap /dev/fb0 test.bmp
> 
> Where bmap is:
> 
> git clone git://github.com/morimoto/bmap.git
> cd bmap/
> git checkout 6f64f8beee1be0c2f57752265a0568706d77794b
> echo "CROSS = arm-linux-gnueabi-" > .config
> make
> 
> And test.bmp is
> http://horms.org/tmp/test.bmp

It looks like th LCDC FB driver doesn't work correctly when IOMMU support is 
enabled. Given that the IOMMU driver seems to be broken and untested anyway 
(see the two fixes I've just sent), my recommendation would be to turn IOMMU 
support off until this can get investigated.

> > > > Using DT-Reference I see nothing relating to fb in dmeg or /dev
> > > > 
> > > > I am using armadillo800eva_defconfig with:
> > > > * CONFIG_MACH_ARMADILLO800EVA disabled
> > > > * CONFIG_MACH_ARMADILLO800EVA_REFERENCE enabled
> > > > * CONFIG_BLK_DEV_INITRD and friends enabled
> > > 
> > > The DT-reference board doesn't enable LCDC.
> > 
> > Understood.

-- 
Regards,

Laurent Pinchart