[PATCH] drm: hdlcd: allow HDLCD to be used without interrupt

[Liviu Dudau]

On Mon, Aug 21, 2017 at 03:45:21PM +0100, Vladimir Murzin wrote:
> On 10/08/17 13:15, Vladimir Murzin wrote:
> > On 26/07/17 11:27, Russell King - ARM Linux wrote:
> >> I suspect the above failure is down to either (a) not having enough
> >> memory available to allocate a 1920x1080 frame buffer, or (b) not
> >> (yet) being able to program the hdlcd pixel clock for this platform,
> >> which is currently hard-coded in DT at 23.75MHz.
> > 
> > Given it is NOMMU it is likely (a). Usually, tweaking FORCE_MAX_ZONEORDER
> > helped me in such cases.
> 
> Ok, with CONFIG_FORCE_MAX_ZONEORDER=12 I see
> 
> [    5.242423] [drm] found ARM HDLCD version r0p0
> [    5.493835] tda998x 2-0070: found TDA19988
> [    5.527771] hdlcd 40205000.hdlcd: bound 2-0070 (ops 0x1470f8)
> [    5.535819] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
> [    5.543478] [drm] No driver support for vblank timestamp query.
> [    7.443189] hdlcd 40205000.hdlcd: fb0:  frame buffer device
> [    7.501975] [drm] Initialized hdlcd 1.0.0 20151021 for 40205000.hdlcd on minor 0
> 
> when display is connected.
> 
> To make fb-test [1] happy I had to apply following diff:
> 
> diff --git a/drivers/gpu/drm/arm/Kconfig b/drivers/gpu/drm/arm/Kconfig
> index 9a18e1b..d4cb1b1 100644
> --- a/drivers/gpu/drm/arm/Kconfig
> +++ b/drivers/gpu/drm/arm/Kconfig
> @@ -10,6 +10,7 @@ config DRM_HDLCD
>         select DRM_ARM
>         select DRM_KMS_HELPER
>         select DRM_KMS_CMA_HELPER
> +       select FB_PROVIDE_GET_FB_UNMAPPED_AREA if !MMU
>         help
>           Choose this option if you have an ARM High Definition Colour LCD
>           controller.
> 
> (The only user of FB_PROVIDE_GET_FB_UNMAPPED_AREA is NOMMU only drivers/gpu/drm/stm/)
> 
> However, I do not see anything on the screen. I'm probably missing something
> obvious, so if you have an idea, please let me know and I can test the patch.

Do you have fbdev/fbcon enabled? If not, then you need some userspace that
makes use of the DRM interface. I usually play with the tests from
libdrm, you can start with modetest.

Best regards,
Liviu

> 
> [1] https://github.com/prpplague/fb-test-app.git 
> 
> Thanks
> Vladimir
> 
> > 
> > Cheers
> > Vladimir
> > 
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel at lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> > 
> 

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