Re: [PATCH 06/11] drm/i915: Add intel_dotclock_calculate()

Ville Syrjälä
2013-09-13T12:44:09Z

On Fri, Sep 13, 2013 at 03:30:51PM +0300, Jani Nikula wrote:
> On Fri, 06 Sep 2013, ville.syrjala@linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >
> > Extract the code to calculate the dotclock from the link clock and M/N
> > values into a new function from ironlake_crtc_clock_get().
> >
> > The new function can be used to calculate the dotclock for both FDI and
> > DP cases.
> >
> > Also simplify the code a bit along the way.
> >
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> > drivers/gpu/drm/i915/intel_display.c | 40 +++++++++++++++---------------------
> > drivers/gpu/drm/i915/intel_drv.h | 2 ++
> > 2 files changed, 19 insertions(+), 23 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > index b3049a6..c393c8e 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -7410,16 +7410,9 @@ static void i9xx_crtc_clock_get(struct intel_crtc *crtc,
> > pipe_config->adjusted_mode.clock = clock.dot;
> > }
> >
> > -static void ironlake_crtc_clock_get(struct intel_crtc *crtc,
> > - struct intel_crtc_config *pipe_config)
> > +int intel_dotclock_calculate(int link_freq,
> > + const struct intel_link_m_n *m_n)
> > {
> > - struct drm_device *dev = crtc->base.dev;
> > - struct drm_i915_private *dev_priv = dev->dev_private;
> > - enum transcoder cpu_transcoder = pipe_config->cpu_transcoder;
> > - int link_freq;
> > - u64 clock;
> > - u32 link_m, link_n;
> > -
> > /*
> > * The calculation for the data clock is:
> > * pixel_clock = ((m/n)*(link_clock * nr_lanes))/bpp
> > @@ -7430,6 +7423,18 @@ static void ironlake_crtc_clock_get(struct intel_crtc *crtc,
> > * link_clock = (m * link_clock) / n
> > */
> >
> > + if (!m_n->link_n)
> > + return 0;
> > +
> > + return div_u64((u64)m_n->link_m * link_freq, m_n->link_n);
> > +}
> > +
> > +static void ironlake_crtc_clock_get(struct intel_crtc *crtc,
> > + struct intel_crtc_config *pipe_config)
> > +{
> > + struct drm_device *dev = crtc->base.dev;
> > + int link_freq;
> > +
> > /*
> > * We need to get the FDI or DP link clock here to derive
> > * the M/N dividers.
> > @@ -7438,21 +7443,10 @@ static void ironlake_crtc_clock_get(struct intel_crtc *crtc,
> > * For DP, it's either 1.62GHz or 2.7GHz.
> > * We do our calculations in 10*MHz since we don't need much precison.
> > */
> > - if (pipe_config->has_pch_encoder)
> > - link_freq = intel_fdi_link_freq(dev) * 10000;
> > - else
> > - link_freq = pipe_config->port_clock;
>
> The new code loses this distinction. I don't know if it matters. Please
> explain.
>
> > -
> > - link_m = I915_READ(PIPE_LINK_M1(cpu_transcoder));
> > - link_n = I915_READ(PIPE_LINK_N1(cpu_transcoder));
> > -
> > - if (!link_m || !link_n)
> > - return;
> > -
> > - clock = ((u64)link_m * (u64)link_freq);
> > - do_div(clock, link_n);
> > + link_freq = intel_fdi_link_freq(dev) * 10000;
> >
> > - pipe_config->adjusted_mode.clock = clock;
> > + pipe_config->adjusted_mode.clock =
> > + intel_dotclock_calculate(link_freq, &pipe_config->fdi_m_n);
>
> I'm not sure if the fear in unwarranted, but can we always be sure
> fdi_m_n has been set?

I seem to have jumped the gun a bit with this patch. Patch 9 will make
it so that we don't call ironlake_crtc_clock_get() except in the PCH
encoder case (could use a rename of the function at that point maybe).
Before patch 9 we still call this guy for non-PCH cases and then it
might fall apart a bit. As the dp_m_n extraction patch appears before
this patch in the series, I think I can just make a slightly fixed
version of this patch. Stay tuned for v2...

--
Ville Syrjälä
Intel OTC