Re: [PATCH 1/2] drm: Stop using drm_vblank_count() as the hw frame counter

From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Vincent ABRIOU <vincent.abriou@st.com>
Cc: Thierry Reding <treding@nvidia.com>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>
Subject: Re: [PATCH 1/2] drm: Stop using drm_vblank_count() as the hw frame counter
Date: Fri, 2 Oct 2015 15:48:10 +0300	[thread overview]
Message-ID: <20151002124810.GN26517@intel.com> (raw)
In-Reply-To: <560E3F77.9080806@st.com>

On Fri, Oct 02, 2015 at 10:25:27AM +0200, Vincent ABRIOU wrote:
> 
> 
> On 09/30/2015 04:14 PM, Ville Syrjälä wrote:
> > On Wed, Sep 30, 2015 at 04:08:02PM +0200, Daniel Vetter wrote:
> >> On Wed, Sep 30, 2015 at 04:46:48PM +0300, ville.syrjala@linux.intel.com wrote:
> >>> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >>>
> >>> drm_vblank_count() returns the software counter. We should not pretend
> >>> it's the hw counter since we use the hw counter to figuere out what the
> >>> software counter value should be. So instead provide a new function
> >>> drm_vblank_no_hw_counter() for drivers that don't have a real hw
> >>> counter. The new function simply returns 0, which is about the only
> >>> thing it can do.
> >>
> >> Shouldn't we instead just make the get_vblank_counter hook optional?
> >
> > Perhaps. But maybe this way would encourage people to go look for a
> > hw frame counter in their hardware?
> >
> >> -Daniel
> >>
> >>>
> >>> Cc: Vincent Abriou <vincent.abriou@st.com>
> >>> Cc: Thierry Reding <treding@nvidia.com>
> >>> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >>> ---
> >>>   drivers/gpu/drm/armada/armada_drv.c          |  2 +-
> >>>   drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_dc.c |  2 +-
> >>>   drivers/gpu/drm/drm_irq.c                    | 17 +++++++++++++++++
> >>>   drivers/gpu/drm/exynos/exynos_drm_drv.c      |  2 +-
> >>>   drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c    |  2 +-
> >>>   drivers/gpu/drm/imx/imx-drm-core.c           |  2 +-
> 
> [..]
> 
> >>> --- a/drivers/gpu/drm/drm_irq.c
> >>> +++ b/drivers/gpu/drm/drm_irq.c
> >>> @@ -1797,3 +1797,20 @@ bool drm_crtc_handle_vblank(struct drm_crtc *crtc)
> >>>      return drm_handle_vblank(crtc->dev, drm_crtc_index(crtc));
> >>>   }
> >>>   EXPORT_SYMBOL(drm_crtc_handle_vblank);
> >>> +
> >>> +/**
> >>> + * drm_vblank_no_hw_counter - "No hw counter" implementation of .get_vblank_counter()
> >>> + * @dev: DRM device
> >>> + * @pipe: CRTC for which to read the counter
> >>> + *
> >>> + * Drivers can plug this into the .get_vblank_counter() function if
> >>> + * there is no useable hardware frame counter available.
> >>> + *
> >>> + * Returns:
> >>> + * 0
> >>> + */
> >>> +u32 drm_vblank_no_hw_counter(struct drm_device *dev, int pipe)
> 
> warning when building the kernel:
> int pipe => unsigned int pipe

Where exactly? The function pointer signature still has a signed int
here, and I was too lazy to go on a rampage to change all the remaining
signed ints to unsigned for the vblank driver hooks.

-- 
Ville Syrjälä
Intel OTC
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