Hi Thierry,
On Tue, Apr 22, 2014 at 1:49 PM, Thierry Reding <thierry.reding at gmail.com> wrote: > On Tue, Apr 22, 2014 at 04:09:11AM +0530, Ajay Kumar wrote: >> Most of the panels need an init sequence as mentioned below: >> -- poweron LCD unit/LCD_EN >> -- start video data >> -- poweron LED unit/BL_EN >> And, a de-init sequence as mentioned below: >> -- poweroff LED unit/BL_EN >> -- stop video data >> -- poweroff LCD unit/LCD_EN >> With existing callbacks for drm panel, we cannot accomodate such panels, >> since only two callbacks, i.e "panel_enable" and panel_disable are supported. >> >> This patch adds: >> -- "pre_enable" callback which can be called before >> the actual video data is on, and then call the "enable" >> callback after the video data is available. >> >> -- "post_disable" callback which can be called after >> the video data is off, and use "disable" callback >> to do something before switching off the video data. >> >> Now, we can easily map the above scenario as shown below: >> poweron LCD unit/LCD_EN = "pre_enable" callback >> poweron LED unit/BL_EN = "enable" callback >> poweroff LED unit/BL_EN = "disable" callback >> poweroff LCD unit/LCD_EN = "post_disable" callback > > I don't like this. What happens when the next panel comes around that > has a yet slightly different requirement? Will we introduce a new > pre_pre_enable() and post_post_disable() function then? > As I have already explained, these 2 callbacks are sufficient enough to take care the power up/down sequence for LVDS and eDP panels. And, definitely having just 2 callbacks "enable" and "disable" is not at all sufficient. I initially thought of using panel_simple_enable from panel-simple driver. But it doesn't go well with case wherein there are 2 regulators(one for LCD and one for LED) a BL_EN signal etc. And, often(Believe me, I have referred to both eDP panel datasheets and LVDS panel datasheets) proper powerup sequence for such panels is as mentioned below: powerup: -- power up the supply (LCD_VCC). -- start video data. -- enable backlight. powerdown -- disable backlight. -- stop video data. -- power off the supply (LCD VCC) For the above cases, if I have to somehow fit in all the required settings, it breaks the sequence and I end up getting glitches during bootup/DPMS. Also, when the drm_bridge can support pre_enable and post_disable, why not drm_panel provide that both should work in tandem? > There's got to be a better way to solve this. > > Thierry Thanks and Regards, Ajay Kumar -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.freedesktop.org/archives/dri-devel/attachments/20140422/366ae5de/attachment.html>
