> -----Original Message----- > From: Ville Syrjälä [mailto:ville.syrj...@linux.intel.com] > Sent: Thursday, October 20, 2016 8:03 PM > To: Nikula, Jani <jani.nik...@intel.com> > Cc: Yang, Libin <libin.y...@intel.com>; Lin, Mengdong > <mengdong....@intel.com>; intel-gfx@lists.freedesktop.org; Zhang, Keqiao > <keqiao.zh...@intel.com>; libin.y...@linux.intel.com; Pandiyan, > Dhinakaran <dhinakaran.pandi...@intel.com>; Zhao, Juan J > <juan.j.z...@intel.com> > Subject: Re: [Intel-gfx] [PATCH RESEND 9/9] drm/i915: set proper N/M in > modeset > > On Thu, Oct 20, 2016 at 02:34:34PM +0300, Jani Nikula wrote: > > On Thu, 20 Oct 2016, "Yang, Libin" <libin.y...@intel.com> wrote: > > >> >> Any particular reason these M/N values are half of what they're > > >> >> in table > > >> >> 2-104 of DP 1.4 spec? (Admittedly the table is an informative > > >> >> example.) > > >> > > > >> > For HDMI, we found only set N is enough. HW then can handle the > > >> remaining. > > >> > > >> I meant, the M and N values in this part of the dp_aud_n_m table > > >> are 1/2 of what they are in the DP spec table. Why? > > > > > > Which table are you meaning? I calculate the values myself. I didn't > > > find the full table in DP spec. I only find the table for 270MHz and > > > 162MHz in Table 2-50: Examples of Maud and Naud Values > > > > Table 2-104 in DP 1.4. Maybe you're looking at an older version of the > > spec. > > So it looks like they used the same M value for all link frequencies in that > example, which for 540M ends up being double what the minimal accurate > value is. But as both M and N are doubled the ratio is still exactly the same.
There is a formula in DP 1.2 spec: Maud/Naud = 512 * fs / f_LS_Clk Suppose all the values meeting the formula is acceptable. > > And there is indeed a 64k and 128k bitrates added as well. Those are not > classified under HBR audio. But as those can't be expressed via short audio > descriptors in the EDID, I don't think they would be accepted by ALSA. Or am > I wrong? I do wonder how they are supposed to be used though since there > must be some way for the sink to advertise them, otherwise I can't see the > point in adding them. Oh, sorry, I was thinking 128k is HBR. I didn't see 64k and 128k description in DP 1.2 spec. Regards, Libin > > -- > Ville Syrjälä > Intel OTC _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
