From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lyude Paul Subject: Re: [PATCH 1/2] drm/nouveau/dispnv04: Grab/put runtime PM refs on DPMS on/off Date: Wed, 07 Aug 2019 19:09:47 -0400 Message-ID: <2a454d971a6c2bc3da730333aacaa420ecddefd6.camel@redhat.com> References: <20190807213304.9255-1-lyude@redhat.com> <20190807213304.9255-2-lyude@redhat.com> <20190807215508.GK7444@phenom.ffwll.local> Reply-To: lyude@redhat.com Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Ilia Mirkin , nouveau , Ben Skeggs , David Airlie , dri-devel , LKML Cc: Daniel Vetter List-Id: dri-devel@lists.freedesktop.org On Wed, 2019-08-07 at 19:06 -0400, Ilia Mirkin wrote: > On Wed, Aug 7, 2019 at 5:55 PM Daniel Vetter wrote: > > On Wed, Aug 07, 2019 at 05:33:00PM -0400, Lyude Paul wrote: > > > The code claims to grab a runtime PM ref when at least one CRTC is > > > active, but that's not actually the case as we grab a runtime PM ref > > > whenever a CRTC is enabled regardless of it's DPMS state. Meaning that > > > we can end up keeping the GPU awake when there are no screens enabled, > > > something we don't really want to do. > > > > > > Note that we fixed this same issue for nv50 a while ago in: > > > > > > commit e5d54f193572 ("drm/nouveau/drm/nouveau: Fix runtime PM leak in > > > nv50_disp_atomic_commit()") > > > > > > Since we're about to remove nouveau_drm->have_disp_power_ref in the next > > > commit, let's also simplify the RPM code here while we're at it: grab a > > > ref during a modeset, grab additional RPM refs for each CRTC enabled by > > > said modeset, and drop an RPM ref for each CRTC disabled by said > > > modeset. This allows us to keep the GPU awake whenever screens are > > > turned on, without needing to use nouveau_drm->have_disp_power_ref. > > > > > > Signed-off-by: Lyude Paul > > > --- > > > drivers/gpu/drm/nouveau/dispnv04/crtc.c | 18 ++++-------------- > > > 1 file changed, 4 insertions(+), 14 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/nouveau/dispnv04/crtc.c > > > b/drivers/gpu/drm/nouveau/dispnv04/crtc.c > > > index f22f01020625..08ad8e3b9cd2 100644 > > > --- a/drivers/gpu/drm/nouveau/dispnv04/crtc.c > > > +++ b/drivers/gpu/drm/nouveau/dispnv04/crtc.c > > > @@ -183,6 +183,10 @@ nv_crtc_dpms(struct drm_crtc *crtc, int mode) > > > return; > > > > > > nv_crtc->last_dpms = mode; > > > + if (mode == DRM_MODE_DPMS_ON) > > > + pm_runtime_get_noresume(dev->dev); > > > + else > > > + pm_runtime_put_noidle(dev->dev); > > > > it's after we filter out duplicate operations, so that part looks good. > > But not all of nouveau's legacy helper crtc callbacks go throuh ->dpms I > > think: nv_crtc_disable doesn't, and crtc helpers use that in preference > > over ->dpms in some cases. > > > > I think the only way to actually hit that path is if you switch an active > > connector from an active CRTC to an inactive one. This implicitly disables > > the crtc (well, should, nv_crtc_disable doesn't seem to shut down hw), and > > I think would leak your runtime PM reference here. At least temporarily. > > > > No idea how to best fix that. Aside from "use atomic" :-) > > Not sure if this is relevant to the discussion at hand, but I'd like > to point out that dispnv04 is for pre-nv50 things, which definitely > didn't support any kind of ACPI-based runtime suspend. I thought it was really suspicious that such an old chipset had any kind of runtime PM, but didn't question the code lol. I guess a more appropriate patch would be to just remove runtime PM support entirely for pre-nv50. Will respin soon and do this. > > -ilia