Re: [PATCH v3 0/4] Enable lspcon support for GEN9 devices

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Jul 20, 2016 at 04:16:30PM +0000, Sharma, Shashank wrote:
> Hi Ville.
> 
> > This thing seems to be missing a lot of stuff:
> > - where is the EDID etc. handling?
> None required for LSPCON as of now.
> The 4k@60 pixel clock support was already added with SKL, so we can see
> a HDMI 4k@60 output already on PCON mode, when connected to a 4k@60 monitor.
> 
> I have started publishing a separate patch series to support HDMI 2.0, started with the new aspect ratio patches here. I was hoping to proceed with EDID changes, once we get these in, else the patch series gets huge and reviewers find it difficult to review. 
> https://patchwork.freedesktop.org/patch/78308/ 
>  
> Plan is to publish in this sequence:
> - Add new aspect ratios
> - Add new 4k modes in DRM EDID
> - Add Scrambling support
> - Add SCDC parsing
> - Add YUV 420 CEA-861-F block parsing
> and so on. 
> 
> > - based on my DDI output_types stuff, I was expecting to see an
> >  lspcon .compute_output_type() hook that returns whether we need
>  >  LS or PCON mode. Can't see anything of the sort here.
> As I explained in the commit message/cover letter LSPCON is no more working selectively on LS/PCON mode.

Oh. Do we have some idea of the power cost?

Curiously when I tried to measure the idle power consumption on my BSW,
DP seemed to be a bit less hungry than HDMI. But I guess the PCON
stuff itself will use some amount of power which might offset any
benefit from using DP on the SoC side.


> We are driving it in always PCON mode, and driver always drives a DP.  So we are driving a DP with separate detection sequence. 
> 
> > Also the main patch [1] of my DDI output_types series still didn't get reviewed...
> Ok, but that should not be a blocker for this series, should it ? 

The encoder->type swithing is still a problem. Though I suppose it will
be fairly well masked if you always have DPCD avaailable.

> 
> Regards
> Shashank
> -----Original Message-----
> From: Ville Syrjälä [mailto:ville.syrjala@linux.intel.com] 
> Sent: Wednesday, July 20, 2016 6:39 PM
> To: Sharma, Shashank <shashank.sharma@intel.com>
> Cc: intel-gfx@lists.freedesktop.org; rodrigo.vivi@gmail.com; Vivi, Rodrigo <rodrigo.vivi@intel.com>; Zanoni, Paulo R <paulo.r.zanoni@intel.com>
> Subject: Re: [PATCH v3 0/4] Enable lspcon support for GEN9 devices
> 
> On Tue, Jul 05, 2016 at 06:35:46PM +0530, Shashank Sharma wrote:
> > LSPCON is essentially a dp++->hdmi adapter with dual mode of operation.
> > 
> > These modes are:
> > - Level Shifter mode: In LS mode, this device works as a type2 
> > dp->hdmi passive dongle, which steps up DP++ output to appropriate HDMI 1.4 signal.
> > This mode doesn't do any conversion at the protocol level.
> > 
> > - Protocol Converter mode: In PCON mode, this device acts as an active 
> > DP++->HDMI 2.0 dongle, which converts the DP++ output to compatible 
> > HDMI 2.0 output. In PCON mode, lspcon can support 4k@60 outputs, using 
> > DP HBR2 mode.
> > 
> > Many of Intel GEN9 devices come with in-built lspcon card in 
> > motherboartd down mode. This patch series adds support for lspcon 
> > devices in I915 driver.
> > 
> > While unit-testing this code, I was able to see a 4k@60 modeset with:
> > - BXT-T board
> > - Single HDMI 4k@60 display (ACER S)
> > - Ubuntu 14.04 desktop
> > 
> > V2: Worked on review comments from Ville
> > - In general, Ville suggested not to use the dual personality of
> >   DDI to drive lspcon, so this patch set drives it just as DP++ display.
> >   There is no separate detection for lspcon (hpd_pulse is good enough), and
> >   its being driven as a DP display with special initialization and EDID
> >   read sequence. To be able to do this, we driving lspcon in PCON mode only,
> >   where it can serve both HDMI1.3/HDMI1.4 sinks as well as 4k@60 capable
> >   HDMI 2.0 sinks. So compared to previous series, there is one patch less,
> >   as we have dropped lspcon detection patch.
> > 
> > 
> > V3: Addressed review comments from Rodrigo
> >     Details available in respective patch.
> > 
> > Shashank Sharma (4):
> >   drm: Helper for lspcon in drm_dp_dual_mode
> >   drm/i915: Add lspcon support for I915 driver
> >   drm/i915: Parse VBT data for lspcon
> >   drm/i915: Enable lspcon initialization
> 
> This thing seems to be missing a lot of stuff:
> - where is the EDID etc. handling?
> None required for LSPCON as of now. The 4k@60 pixel clock support was already added with SKL
> - based on my DDI output_types stuff, I was expecting to see an
>   lspcon .compute_output_type() hook that returns whether we need
>   LS or PCON mode. Can't see anything of the sort here.
> 
> Also the main patch [1] of my DDI output_types series still didn't get reviewed...
> 
> [1] https://patchwork.freedesktop.org/patch/94581/
> 
> > 
> >  drivers/gpu/drm/drm_dp_dual_mode_helper.c | 103 +++++++++++++++++++++
> >  drivers/gpu/drm/i915/Makefile             |   1 +
> >  drivers/gpu/drm/i915/i915_drv.h           |   5 ++
> >  drivers/gpu/drm/i915/intel_bios.c         |  49 ++++++++++
> >  drivers/gpu/drm/i915/intel_ddi.c          |  29 +++++-
> >  drivers/gpu/drm/i915/intel_drv.h          |  13 ++-
> >  drivers/gpu/drm/i915/intel_lspcon.c       | 145 ++++++++++++++++++++++++++++++
> >  include/drm/drm_dp_dual_mode_helper.h     |  26 ++++++
> >  8 files changed, 369 insertions(+), 2 deletions(-)  create mode 
> > 100644 drivers/gpu/drm/i915/intel_lspcon.c
> > 
> > --
> > 1.9.1
> 
> --
> Ville Syrjälä
> Intel OTC

-- 
Ville Syrjälä
Intel OTC
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