[PATCH 2/2] RFC: drm/pl111: Support using the VGA bridge as fallback

[Daniel Vetter]

On Fri, Sep 01, 2017 at 11:46:29AM +0200, Linus Walleij wrote:
> If we cannot find a panel, assume that the output from the
> PL111 is connected directly to a "dumb" VGA connector,
> so look up the connector from that bridge.
> 
> Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
> ---
> This is how the new API is used in the PL111.
> ---
>  drivers/gpu/drm/pl111/Kconfig     | 1 +
>  drivers/gpu/drm/pl111/pl111_drv.c | 3 +++
>  2 files changed, 4 insertions(+)
> 
> diff --git a/drivers/gpu/drm/pl111/Kconfig b/drivers/gpu/drm/pl111/Kconfig
> index e5e2abd66491..82cb3e60ddc8 100644
> --- a/drivers/gpu/drm/pl111/Kconfig
> +++ b/drivers/gpu/drm/pl111/Kconfig
> @@ -8,6 +8,7 @@ config DRM_PL111
>  	select DRM_GEM_CMA_HELPER
>  	select DRM_BRIDGE
>  	select DRM_PANEL_BRIDGE
> +	select DRM_DUMB_VGA_DAC
>  	select VT_HW_CONSOLE_BINDING if FRAMEBUFFER_CONSOLE
>  	help
>  	  Choose this option for DRM support for the PL111 CLCD controller.
> diff --git a/drivers/gpu/drm/pl111/pl111_drv.c b/drivers/gpu/drm/pl111/pl111_drv.c
> index f5bc6f160e60..6db423bbd84e 100644
> --- a/drivers/gpu/drm/pl111/pl111_drv.c
> +++ b/drivers/gpu/drm/pl111/pl111_drv.c
> @@ -67,6 +67,7 @@
>  #include <drm/drm_of.h>
>  #include <drm/drm_bridge.h>
>  #include <drm/drm_panel.h>
> +#include <drm/dumb_vga_dac.h>
>  
>  #include "pl111_drm.h"
>  #include "pl111_versatile.h"
> @@ -128,6 +129,8 @@ static int pl111_modeset_init(struct drm_device *dev)
>  	if (panel) {
>  		priv->panel = panel;
>  		priv->connector = panel->connector;
> +	} else {
> +		priv->connector = drm_dumb_vga_get_connector(bridge);

Why do you need to set this? The only code I could find tries to set
polarity values from bus_flags, and for VGA I'd assume you want to instead
key this off the mode?

Wrt the more general problem: They way we solve this in the i915 atomic
framework is that the various ->fixup calls fill out relevant fields in
the drm_crtc_state. I guess we could add an ->atomic_check to bridges, add
a bus_flags to drm_crtc_state (or maybe just let everyone patch up
adjusted_mode->flags) instead?

Cheers, Daniel
>  	}
>  	priv->bridge = bridge;
>  
> -- 
> 2.13.5
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch