On Thu, 2018-02-01 at 12:34 +0100, Hans de Goede wrote:
> Hi All,
> 
> For the "Improved Laptop Battery Life" feature:
> https://fedoraproject.org/wiki/Changes/ImprovedLaptopBatteryLife
> 
> I'm working on for Fedora 28 I would like to also try and enable
> Panel Self Refresh on laptops with Intel graphics, some quick tests
> have shown this to save another 0.5W (when idle / nothing on the
> screen changes). This is currently off be default because it is
> known to cause issues on some devices. So I think we will probably
> need a white- or black-list. But first we need more data on this.
> 
> If you can spare 10 minutes, please see my blogpost for how to test
> this and send me a mail with the info request in the blogpost:
> https://hansdegoede.livejournal.com/18653.html

ThinkPad X1 Carbon 3rd gen (i7-5600U) kernel 4.14.14-300.fc27.x86_64. 
I added i915.enable_psr=1 but it doesn't seem to have enabled PSR on
the panel:

Sink_Support: no
Source_OK: no
Enabled: no
Active: no
Busy frontbuffer bits: 0x000
Re-enable work scheduled: no
Main link in standby mode: no
HW Enabled & Active bit: no
Performance_Counter: 0

Shouldn't Sink_Support:no mean that the panel doesn't support PSR?  At
least that's what would be implied by intel_dp.c:

        /* Check if the panel supports PSR */
        drm_dp_dpcd_read(&intel_dp->aux, DP_PSR_SUPPORT,
                         intel_dp->psr_dpcd,
                         sizeof(intel_dp->psr_dpcd));
        if (intel_dp->psr_dpcd[0] & DP_PSR_IS_SUPPORTED) {
                dev_priv->psr.sink_support = true;
                DRM_DEBUG_KMS("Detected EDP PSR Panel.\n");
        }

        if (INTEL_GEN(dev_priv) >= 9 &&
            (intel_dp->psr_dpcd[0] & DP_PSR2_IS_SUPPORTED)) {
                uint8_t frame_sync_cap;

                dev_priv->psr.sink_support = true;

Dan
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