[U-Boot] [RESEND] video: bcm2835: add support for reading from the video-mode environment variable

[Stephen Warren]

On 01/12/2017 01:57 AM, Brian Masney wrote:
> The bcm2835 driver polls the monitor and selects the highest resolution
> that is available. This patch allows optionally setting the video-mode
> environment variable so that a different video resolution can be used.
> If the environment variable is not specified, then it will fall back to
> using the old behavior of using the maximum allowable resolution.
>
> This patch is needed to fix an issue booting an upstream Linux kernel
> on a Raspberry Pi 2 with a Pi Top screen. Previously, the bcm2835 would
> select the 1366x768 resolution (which is a supported resolution),
> however the screen would be unreadable. (See
> https://www.flickr.com/photos/masneyb/30942037416/ for picture). Using
> this patch, the resolution 1024x768 can be selected and is readable on
> the screen.

Doesn't this mean that the RPi firmware is reporting the wrong 
resolution? If so, isn't the correct fix to get an updated firmware that 
reports the correct resolution, rather than patching each piece of SW to 
ignore the FW-reported resolution? Or, if this is caused by incorrect 
EDID in the Pi Top, then fix the EDID EEPROM on that.

Perhaps there are other use-cases for using a non-default resolution, 
but to support that, you'd need to make a call into the FW to request 
and configure that non-default resolution, not just ignore what 
resolution the FW programmed.