On Mon, Apr 15, 2013 at 06:59:58PM +0200, Daniel Vetter wrote: > On Mon, Apr 15, 2013 at 6:38 PM, Jani Nikula <jani.nikula at intel.com> wrote: > > On Mon, 15 Apr 2013, Chris Wilson <chris at chris-wilson.co.uk> wrote: > >> On Fri, Apr 12, 2013 at 03:18:37PM +0300, Jani Nikula wrote: > >>> Backlight data and registers are fiddled through LVDS/eDP modeset > >>> enable/disable hooks, backlight sysfs files, asle interrupts, and register > >>> save/restore. Protect the backlight related registers and driver private > >>> fields using a spinlock. > >>> > >>> The locking in register save/restore covers a little more than is strictly > >>> necessary, including non-modeset case, for simplicity. > >>> > >>> v2: Cover register access, save/restore, i915_read_blc_pwm_ctl() and code > >>> paths leading there. > >>> > >>> Signed-off-by: Jani Nikula <jani.nikula at intel.com> > >> > >> Looks reasonable. > >> > >> intel_panel_actually_set_backlight() should have a WARN_ON(!spinlocked); > >> > >> The irqness of the register writes scares me slightly - since the IRQ in > >> question is from ACPI and we have a few bug reports along the lines of > >> "backlight makes the entire system sluggish" i.e. commonly associated > >> with bad interrupt handling. Whilst you are looking at updating the > >> backlight programming, can you look at pushing the writes from out > >> of the interrupt handler? > > > > So, add a work to do the register writes, and change the spinlock into a > > mutex while at it? Should be fairly simple, if you think that's the way > > to go. > > I think I'll go ahead with the spinlock fix here for 3.10 and we can > look into offloading this all for 3.11. Also, Chris do you remember > one of these reports - I've kinda never noticed that particular kind > of suck? I maybe way off the mark and the cause is likely just to be a sucky ACPI firmware: https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/1019370 spinlock -> mutex + workqueue would mitigate against any bad firmware being run under irq context. -Chris -- Chris Wilson, Intel Open Source Technology Centre
