Re: [PATCH 10/11] drm/i915: Improve PSR debugfs status.

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Jun 02, 2014 at 11:54:10PM +0530, Vijay Purushothaman wrote:
> On 5/16/2014 5:43 AM, Rodrigo Vivi wrote:
> >Now we have the active/inactive state for exit and this actually changes the
> >HW enable bit the status was a bit confusing for users. So let's provide
> >more info.
> >
> >Signed-off-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>
> >---
> >  drivers/gpu/drm/i915/i915_debugfs.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> >diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> >index 6636ca2..0ca9376 100644
> >--- a/drivers/gpu/drm/i915/i915_debugfs.c
> >+++ b/drivers/gpu/drm/i915/i915_debugfs.c
> >@@ -1975,10 +1975,12 @@ static int i915_edp_psr_status(struct seq_file *m, void *data)
> >
> >  	seq_printf(m, "Sink_Support: %s\n", yesno(dev_priv->psr.sink_support));
> >  	seq_printf(m, "Source_OK: %s\n", yesno(dev_priv->psr.source_ok));
> >+	seq_printf(m, "Enabled: %s\n", yesno(dev_priv->psr.enabled));
> >+	seq_printf(m, "Active: %s\n", yesno(dev_priv->psr.active));
> >
> >  	enabled = HAS_PSR(dev) &&
> >  		I915_READ(EDP_PSR_CTL(dev)) & EDP_PSR_ENABLE;
> >-	seq_printf(m, "Enabled: %s\n", yesno(enabled));
> >+	seq_printf(m, "HW Enabled & Active bit: %s\n", yesno(enabled));
> >
> >  	if (HAS_PSR(dev))
> >  		psrperf = I915_READ(EDP_PSR_PERF_CNT(dev)) &
> 
> Please remove all references to PSR performance counter. This register is
> primarily meant as a debug register and its implementation is broken in the
> h/w. Whenever the cdclk is gated to save power, the performance counter is
> stopped. But when the clk is re-enabled it doesn't reset the counter. This
> unnecessarily confuses the end users.. When the system goes through suspend
> / resume cycle the performance counter most likely will transition from a
> non-zero value to zero.. I already received few queries from our customers
> related to this performance customer and they refuse to believe me when i
> tell them PSR is still functional when the performance counter reports 0 :-)

We expose other such perf registers and imo this is handy for debugging.
Also we have a big push to expose all this perf stuff recently ...

Imo we should keep this, if we can. If confused customers noodle around in
debugfs without clue, maybe they shouldn't.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch