[Intel-gfx] [PATCH] drm/i915: decouple runtime PM enablement from DMC presence

[Rodrigo Vivi]

On Thu, Jun 15, 2017 at 9:30 AM, Imre Deak <imre.deak at intel.com> wrote:
> Yes, probably because i915 runtime PM as whole is disabled without DMC,
> so we won't turn off display side power wells either; but D3 still won't
> make a difference.
>
> The problem with not having DMC is that with that you'll prevent system
> level power saving that is deeper package C states.

But if there are still power savings proved even without reaching the
deeper package C states
I believe it is worth allowing RPM to work without requiring DMC, no?!


>
> --Imre
>
> On Thu, Jun 15, 2017 at 07:16:25PM +0300, Atwood, Matthew S wrote:
>> On ChromeOS I've tested a couple hundred thousand iterations, during
>> their Power Load test (Google's battery claim test) an avg of 400 mW
>> is saved when RPM is turned on with DMC missing vs both turned off, So
>> i think D3 is definitely relevant even without DMC.
>> ________________________________________
>> From: Deak, Imre
>> Sent: Wednesday, June 14, 2017 1:17 PM
>> To: Rodrigo Vivi
>> Cc: Atwood, Matthew S; intel-gfx at lists.freedesktop.org; marcheu at google.com; Matt Atwood
>> Subject: Re: [Intel-gfx] [PATCH] drm/i915: decouple runtime PM enablement from DMC presence
>>
>> On Wed, Jun 14, 2017 at 01:02:27PM -0700, Rodrigo Vivi wrote:
>> > On Wed, Jun 14, 2017 at 10:55 AM, Imre Deak <imre.deak at intel.com> wrote:
>> > > On Wed, Jun 14, 2017 at 08:40:55PM +0300, Atwood, Matthew S wrote:
>> > >> intel_csr_load_program can fail (if not supported by SoC, or if file
>> > >> is size 0)
>> > >
>> > > Those are really just sanity checks, they can't happen normally. We
>> > > should actually convert them to be WARNs.
>> > >
>> > >> and theres no conditional that it succeeds before releasing
>> > >> power_put on POWER_DOMAIN_INIT, enabling runtime PM.
>> > >
>> > > It can't fail during loading, HAS_CSR() is already checked in
>> > > intel_csr_ucode_init() and dev_priv->csr.dmc_payload is checked right
>> > > before calling intel_csr_load_program().
>> > >
>> > >> As long as the driver *thinks* it has a valid path to a DMC firmware
>> > >> this will execute.
>> > >>
>> > >> "without DMC loaded we want to keep runtime PM disabled" - Why?
>> > >
>> > > There is no reason to support that configuration.
>> >
>> > What if someone doesn't really want to use DMC but still wants D3hot?
>>
>> D3 in itself won't result in power saving you need to enable DC6/9 for
>> that. I'm not even sure if it's even valid to enter PCI D3 without
>> enabling these states first. And for that you need the firmware.
>>
>> >
>> > >
>> > >> ________________________________________
>> > >> From: Deak, Imre
>> > >> Sent: Wednesday, June 14, 2017 10:33 AM
>> > >> To: Atwood, Matthew S
>> > >> Cc: intel-gfx at lists.freedesktop.org; marcheu at google.com; Matt Atwood
>> > >> Subject: Re: [Intel-gfx] [PATCH] drm/i915: decouple runtime PM enablement from DMC presence
>> > >>
>> > >> On Wed, Jun 14, 2017 at 10:12:21AM -0700, matthew.s.atwood at intel.com wrote:
>> > >> > From: Matt Atwood <matthew.s.atwood at intel.corp-partner.google.com>
>> > >> >
>> > >> > Runtime PM is disabled when DMC firmware is not present. Runtime PM is still
>> > >> > enabled even if DMC firmware fails to load.
>> > >>
>> > >> Hm, that would be a bug, but I can't see how it can happen; could you
>> > >> explain? We get a runtime PM reference in intel_csr_ucode_init() and
>> > >> only put it if we loaded the firmware successfully.
>> > >>
>> > >> > This patch enables runtime PM to be enabled if DMC firmware is not present.
>> > >>
>> > >> Without DMC loaded we want to keep runtime PM disabled.
>> > >>
>> > >> --Imre
>> > >>
>> > >> >
>> > >> > Signed-off-by: Matt Atwood <matthew.s.atwood at intel.corp-partner.google.com>
>> > >> > ---
>> > >> >  drivers/gpu/drm/i915/intel_csr.c | 7 +++----
>> > >> >  1 file changed, 3 insertions(+), 4 deletions(-)
>> > >> >
>> > >> > diff --git a/drivers/gpu/drm/i915/intel_csr.c b/drivers/gpu/drm/i915/intel_csr.c
>> > >> > index 965988f..3e4e705 100644
>> > >> > --- a/drivers/gpu/drm/i915/intel_csr.c
>> > >> > +++ b/drivers/gpu/drm/i915/intel_csr.c
>> > >> > @@ -411,8 +411,6 @@ static void csr_load_work_fn(struct work_struct *work)
>> > >> >       if (dev_priv->csr.dmc_payload) {
>> > >> >               intel_csr_load_program(dev_priv);
>> > >> >
>> > >> > -             intel_display_power_put(dev_priv, POWER_DOMAIN_INIT);
>> > >> > -
>> > >> >               DRM_INFO("Finished loading DMC firmware %s (v%u.%u)\n",
>> > >> >                        dev_priv->csr.fw_path,
>> > >> >                        CSR_VERSION_MAJOR(csr->version),
>> > >> > @@ -420,10 +418,11 @@ static void csr_load_work_fn(struct work_struct *work)
>> > >> >       } else {
>> > >> >               dev_notice(dev_priv->drm.dev,
>> > >> >                          "Failed to load DMC firmware"
>> > >> > -                        " [" FIRMWARE_URL "],"
>> > >> > -                        " disabling runtime power management.\n");
>> > >> > +                        " [" FIRMWARE_URL "]");
>> > >> >       }
>> > >> >
>> > >> > +     intel_display_power_put(dev_priv, POWER_DOMAIN_INIT);
>> > >> > +
>> > >> >       release_firmware(fw);
>> > >> >  }
>> > >> >
>> > >> > --
>> > >> > 2.7.4
>> > >> >
>> > >> > _______________________________________________
>> > >> > Intel-gfx mailing list
>> > >> > Intel-gfx at lists.freedesktop.org
>> > >> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>> > >>
>> > > _______________________________________________
>> > > Intel-gfx mailing list
>> > > Intel-gfx at lists.freedesktop.org
>> > > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>> >
>> >
>> >
>> > --
>> > Rodrigo Vivi
>> > Blog: http://blog.vivi.eng.br
>>



-- 
Rodrigo Vivi
Blog: http://blog.vivi.eng.br