Re: [PATCH 1/7 resend] drm/i915: Add the support of eDP on DP-D for Ibex/CPT

[ykzhao <yakui.zhao@intel.com>]

On Sat, 2010-06-12 at 16:28 +0800, Chris Wilson wrote:
> On Sat, 12 Jun 2010 14:32:21 +0800, Zhenyu Wang <zhenyuw@linux.intel.com> wrote:
> > From: Zhao Yakui <yakui.zhao@intel.com>
> > 
> > This one adds support for eDP that connected on PCH DP-D port
> > instead of CPU DP-A port, and only DP-D port could be used for eDP.
> > 
> > https://bugs.freedesktop.org/show_bug.cgi?id=27220
> > 
> > Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
> > Tested-by: Jan-Hendrik Zab <jan@jhz.name>
> > Tested-by: Templar <templar@rshc.de>
> > Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
> > ---
> [snip]
> >  static void
> > -intel_dp_compute_m_n(int bytes_per_pixel,
> > +intel_dp_compute_m_n(int bpp,
> >  		     int nlanes,
> >  		     int pixel_clock,
> >  		     int link_clock,
> >  		     struct intel_dp_m_n *m_n)
> >  {
> >  	m_n->tu = 64;
> > -	m_n->gmch_m = pixel_clock * bytes_per_pixel;
> > +	m_n->gmch_m = (pixel_clock * bpp) >> 3;
> >  	m_n->gmch_n = link_clock * nlanes;
> >  	intel_reduce_ratio(&m_n->gmch_m, &m_n->gmch_n);
> >  	m_n->link_m = pixel_clock;
> 
> This rounds the gmch_m down. Is this correct? And how close to overflow
> is pixel_clock today?

The bpp is the abbreviation of bits per pixel and this is not round
down. It is only to convert the bits per second to bytes per second,
which will be used to calculation the DP M/N .

> -ickle
>