[Intel-gfx] [PATCH v3 0/4] Enable lspcon support for GEN9 devices

Thu Jul 21 04:33:19 UTC 2016

> 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.
You are right, the power side would be slightly higher than the LS mode. 
But there were following cases where we were supposed to be on PCON mode, regardless of pixel clock of requested mode:
- If monitor is HDCP 2.2 capable
- If monitor is trying YUV 420 playback
- If clock > 297 Mhz

So there were lesses cases left to keep LSPCON in LS mode. 
When we compared the code complexity of maintaining LS and PCON mode both, with the use cases, we thought it would be simpler and better to be in PCON mode. 

> The encoder->type swithing is still a problem. Though I suppose it will be fairly well masked if you always have DPCD avaailable.
Not really, now we are always in DP mode. So display controller will be always driving as encoder->type = DP. 
The only changes required now is:
- During the bootup, detect presence of a LSPCON based on VBT, and mark it. 
- During EDID read, if this is LSPCON port, use a separate i2c adapter (well suggested by you in previous review comments :))
- During AVI IF writes, write into LSPCON registers, instead of / on top of display registers. 

Do you think its ok to be going now ? Any further suggestions are welcome. 

Regards
Shashank 
-----Original Message-----
From: Ville Syrjälä [mailto:ville.syrjala at linux.intel.com] 
Sent: Wednesday, July 20, 2016 10:21 PM
To: Sharma, Shashank <shashank.sharma at intel.com>
Cc: intel-gfx at lists.freedesktop.org; rodrigo.vivi at gmail.com; Vivi, Rodrigo <rodrigo.vivi at intel.com>; Zanoni, Paulo R <paulo.r.zanoni at intel.com>
Subject: Re: [PATCH v3 0/4] Enable lspcon support for GEN9 devices

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 at 60 pixel clock support was already added with SKL, so we can 
> see a HDMI 4k at 60 output already on PCON mode, when connected to a 4k at 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 at linux.intel.com]
> Sent: Wednesday, July 20, 2016 6:39 PM
> To: Sharma, Shashank <shashank.sharma at intel.com>
> Cc: intel-gfx at lists.freedesktop.org; rodrigo.vivi at gmail.com; Vivi, 
> Rodrigo <rodrigo.vivi at intel.com>; Zanoni, Paulo R 
> <paulo.r.zanoni at 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 at 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 at 60 modeset with:
> > - BXT-T board
> > - Single HDMI 4k at 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 at 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 at 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