Re: [PATCH] OMAPDSS: Check if RPM enabled before trying to change state

On Mon, 2012-06-25 at 18:12 +0530, Rajendra Nayak wrote:

On Monday 25 June 2012 06:00 PM, Tomi Valkeinen wrote:

quoted

On Mon, 2012-06-25 at 15:05 +0300, Grazvydas Ignotas wrote:

quoted

On Mon, Jun 25, 2012 at 9:20 AM, Tomi Valkeinen[off-list ref]  wrote:

quoted

On Sat, 2012-06-23 at 13:36 +0530, jaswinder.singh@linaro.org wrote:

quoted

  Currenlty HDMI fails to come up in the suspend-resume path.
This patch helps that real-world scenario.

What is the problem there? It'd be good to explain the problem in the
patch description. Does the pm_runtime_get return -EACCES?

On slightly different but related issue, currently OMAPDSS always
spits lots of backtraces when it's compiled without CONFIG_PM_RUNTIME,
because pm_runtime_put* always return -ENOSYS without
CONFIG_PM_RUNTIME. So something like this patch proposes is needed, or
maybe WARN_ON should check for -ENOSYS, I don't know..

Hmm. I guess I'm missing some understanding about runtime PM. omapdss
uses runtime PM to enable the underlying DSS hardware. If there's no
runtime PM, how does the driver work? Or is it the job of
hwmod/omap_device to keep all the hardware always enabled if runtime PM
is not compiled in?

Yes, the below trick keeps all hwmods always enabled post the initial
setup if runtime PM is disabled.

from arch/arm/mach-omap2/io.c

static void __init omap_hwmod_init_postsetup(void)
{
         u8 postsetup_state;

         /* Set the default postsetup state for all hwmods */
#ifdef CONFIG_PM_RUNTIME
         postsetup_state = _HWMOD_STATE_IDLE;
#else
         postsetup_state = _HWMOD_STATE_ENABLED;
#endif
         omap_hwmod_for_each(_set_hwmod_postsetup_state, &postsetup_state);

         omap_pm_if_early_init();
}

Ah, ok, thanks.

Do you know how the drivers should handle CONFIG_PM_RUNTIME=n?
Are they supposed to handle the error values returned by runtime PM
functions somehow, or should they use #ifdef CONFIG_PM_RUNTIME?

Both options sound a bit difficult to me... With the first one it's
difficult to see if there was an actual error and we should somehow
react to it, or is everything fine and we just shouldn't care about
runtime PM. The second one requires ifdefs in many places.

 Tomi