Re: [PATCH 1/2] OMAP: DSS2: enable generic panel configuration modification

Tomi,

Any thoughts?


On 07/27/10 16:59, Igor Grinberg wrote:

On 07/27/10 11:00, Tomi Valkeinen wrote:
  

quoted

On Mon, 2010-07-26 at 12:34 +0200, ext Igor Grinberg wrote:
  
    

quoted

This patch enables platforms to modify the dss device configuration
of the generic panel.

Signed-off-by: Igor Grinberg <redacted>
Signed-off-by: Mike Rapoport <redacted>
---
 drivers/video/omap2/displays/panel-generic.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/video/omap2/displays/panel-generic.c b/drivers/video/omap2/displays/panel-generic.c
index 300eff5..ad80dd0 100644
--- a/drivers/video/omap2/displays/panel-generic.c
+++ b/drivers/video/omap2/displays/panel-generic.c

@@ -66,7 +66,7 @@ static void generic_panel_power_off(struct omap_dss_device *dssdev)
 
 static int generic_panel_probe(struct omap_dss_device *dssdev)
 {
-	dssdev->panel.config = OMAP_DSS_LCD_TFT;
+	dssdev->panel.config |= OMAP_DSS_LCD_TFT;
 	dssdev->panel.timings = generic_panel_timings;
 
 	return 0;
    
      

I don't like this. Panel driver should be the one which decides the
config.
  
    

I agree with this in most cases, but not always.
There are certain transmitters (like TI TFP410 dvi transmitter found
on cm-t35 and other boards) that can have some of their parameters
defined by hardware (strapped), so only the platform knows the correct
values for them.
One of such parameters is the edge of the clock sampling.

  

quoted

I think a better solution is to make panel-generic configurable, which
has been discussed a bit some time ago on l-o.
  
    

No doubt about that :)

  

quoted

Briefly:

- Add a struct for the configuration variables (a bit like
arch/arm/plat-omap/include/plat/nokia-dsi-panel.h).

- Fill the struct in the board file, and pass it to the panel driver via
omap_dss_device->data pointer.

- The panel driver get the struct and uses it to do whatever
configuration it needs.
  
    

This is more or less what I've been thinking of, but with slight addition:
the panel driver should have a defaults for all the parameters,
so there will be no need to provide the whole parameters list,
just the ones that are different.

  

quoted

I think there are two ways to implement this:

1) Have lots of fields in the struct, including video timings and video
signaling information, and the driver uses these directly.
  
    

This seems like a good choice for better flexibility and
provides an easy way of dealing with the issues, I've described above.

  

quoted

2) Have a panel name in the struct, and the panel driver contains a
static list of panels, including configurations for those panels, and
the driver selects the configuration based on the panel name given from
the board file. (like drivers/video/omap2/displays/panel-taal.c does,
except there's currently only one panel defined).
  
    

This approach does not deal with the dvi transmitters issue above,
unless there will be possibility to define some kind of platform data.
Also, if we have a static list of panels with their configurations,
there could be panels with (almost) the same parameters defined
for a couple of times.

  

quoted

While 1. gives perhaps slightly easier configuration, as you just edit
the board file, I'd go for 2. because the required configuration is
really defined by the panel/chip being used, and so the board file
should just state which panel/chip we have, and the driver handles the
rest.
    

Well, unfortunately, it is not :(

  

quoted

 And 2. makes it also easier to use the same panel/chip on multiple
boards.

Implementing this would allow us to remove some panel drivers which
currently are 99% copies of each other.

 Tomi

  
    

My idea is:
generic driver will have built-in defaults, that can
(but not necessarily will) be overridden by platform (or other) code
on a parameter basis.
This will allow other panels (like tdo35s) reuse the generic driver
without the need for their special driver.

What do you think of it?

  

-- 
Regards,
Igor.