From: Vinod Koul <vkoul@kernel.org>
To: Marijn Suijten <marijn.suijten@somainline.org>
Cc: Jonathan Marek <jonathan@marek.ca>,
Jeffrey Hugo <jeffrey.l.hugo@gmail.com>,
David Airlie <airlied@linux.ie>,
linux-arm-msm@vger.kernel.org,
Konrad Dybcio <konrad.dybcio@somainline.org>,
linux-kernel@vger.kernel.org,
Abhinav Kumar <abhinavk@codeaurora.org>,
Bjorn Andersson <bjorn.andersson@linaro.org>,
Rob Clark <robdclark@gmail.com>,
dri-devel@lists.freedesktop.org, Daniel Vetter <daniel@ffwll.ch>,
Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
freedreno@lists.freedesktop.org,
Sumit Semwal <sumit.semwal@linaro.org>
Subject: Re: [Freedreno] [PATCH v3 12/13] drm/msm/dsi: Add support for DSC configuration
Date: Tue, 22 Mar 2022 22:46:50 +0530 [thread overview]
Message-ID: <YjoEgpAZAwM8hWEa@matsya> (raw)
In-Reply-To: <20220217151142.sbp6wslxbxeohsgf@SoMainline.org>
On 17-02-22, 16:11, Marijn Suijten wrote:
> Hi Vinod,
>
> Thanks for taking time to go through this review, please find some
> clarifications below.
>
> On 2022-02-17 16:44:04, Vinod Koul wrote:
> > Hi Marijn,
> >
> > On 11-12-21, 01:03, Marijn Suijten wrote:
> >
> > > > +static int dsi_dsc_update_pic_dim(struct msm_display_dsc_config *dsc,
> > > > + int pic_width, int pic_height)
> > >
> > > This function - adopted from downstream - does not seem to perform a
> > > whole lot, especially without the modulo checks against the slice size.
> > > Perhaps it can be inlined?
> >
> > Most of the code here is :)
> >
> > This was split from downstream code to check and update dimension. We
> > can inline this, or should we leave that to compiler. I am not a very
> > big fan of inlining...
>
> It doesn't seem beneficial to code readability to have this function,
> which is only called just once and also has the same struct members read
> in a `DBG()` directly, abstracted away to a function. Not really
> concerned about generated code/performance FWIW.
>
> Also note that the caller isn't checking the `-EINVAL` result...
I have made this void inline.
> > >
> > > > +{
> > > > + if (!dsc || !pic_width || !pic_height) {
> > > > + pr_err("DSI: invalid input: pic_width: %d pic_height: %d\n", pic_width, pic_height);
> > > > + return -EINVAL;
> > > > + }
> > > > +
> > > > + dsc->drm->pic_width = pic_width;
> > > > + dsc->drm->pic_height = pic_height;
> > > > +
> > > > + return 0;
> > > > +}
> > > > +
> > > > static void dsi_timing_setup(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
> > > > {
> > > > struct drm_display_mode *mode = msm_host->mode;
> > > > @@ -940,7 +954,68 @@ static void dsi_timing_setup(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
> > > > hdisplay /= 2;
> > > > }
> > > >
> > > > + if (msm_host->dsc) {
> > > > + struct msm_display_dsc_config *dsc = msm_host->dsc;
> > > > +
> > > > + /* update dsc params with timing params */
> > > > + dsi_dsc_update_pic_dim(dsc, mode->hdisplay, mode->vdisplay);
>
> That is, the result code here should be checked (or function inlined).
This function return void, so no point in checking
> > > > +
> > > > + /* we do the calculations for dsc parameters here so that
> > > > + * panel can use these parameters
> > > > + */
> > > > + dsi_populate_dsc_params(dsc);
> > > > +
> > > > + /* Divide the display by 3 but keep back/font porch and
> > > > + * pulse width same
> > > > + */
> > >
> > > A more general nit on the comments in this patch series: it is
> > > appreciated if comments explain the rationale rather than - or in
> > > addition to - merely paraphrasing the code that follows.
> >
> > Yes it might be the case here, but in this case I wanted to explicitly
> > point out hat we need to divide display by 3...
>
> The main point here is justifying _why_ there's a division by 3 for the
> active portion of the signal, I presume that's the compression ratio
> (having not read into the DSC compression standard yet at all)?
I have updated this comment
> > > > + if (msm_host->dsc) {
> > > > + struct msm_display_dsc_config *dsc = msm_host->dsc;
> > > > + u32 reg, reg_ctrl, reg_ctrl2;
> > > > + u32 slice_per_intf, bytes_in_slice, total_bytes_per_intf;
> > > > +
> > > > + reg_ctrl = dsi_read(msm_host, REG_DSI_COMMAND_COMPRESSION_MODE_CTRL);
> > > > + reg_ctrl2 = dsi_read(msm_host, REG_DSI_COMMAND_COMPRESSION_MODE_CTRL2);
> > >
> > > Shouldn't old values be masked out first, before writing new bits or
> > > values below? The video-mode variant doesn't read back old register
> > > values.
> >
> > This follows downstream where the registers are read, modified and
> > written back
>
> Are you sure about this? The register values are never cleared, meaning
> that only bits get added through the `|=` below but never unset - unless
> downstream clears these registers elsewhere before ending up in (their
> equivalent of) dsi_timing_setup.
I have modified video mode to write and not read now. For command mode
all bits are set to some value so no need to mask old values for that
> Thanks. I forgot to mention: there seem to be a lot of similarities
> between the video and commandmode computations, can those possibly be
> factored out of the if-else to save on duplication and accidental
> mismatches like these?
Thanks, this was a good suggestion and am happy to report that I have
incorporated this and indeed code looks better
--
~Vinod
next prev parent reply other threads:[~2022-03-22 17:17 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-16 6:22 [PATCH v3 00/13] drm/msm: Add Display Stream Compression Support Vinod Koul
2021-11-16 6:22 ` [PATCH v3 01/13] drm/msm/dsi: add support for dsc data Vinod Koul
2021-11-24 15:53 ` Dmitry Baryshkov
2021-11-30 1:14 ` [Freedreno] " Abhinav Kumar
2021-11-16 6:22 ` [PATCH v3 02/13] drm/msm/disp/dpu1: Add support for DSC Vinod Koul
2021-11-24 15:35 ` Dmitry Baryshkov
2021-11-16 6:22 ` [PATCH v3 03/13] drm/msm/disp/dpu1: Add support for DSC in pingpong block Vinod Koul
2022-02-17 21:54 ` Marijn Suijten
2022-02-17 22:06 ` Marijn Suijten
2022-02-17 22:12 ` Dmitry Baryshkov
2022-02-17 22:39 ` Marijn Suijten
2021-11-16 6:22 ` [PATCH v3 04/13] drm/msm/disp/dpu1: Add DSC for SDM845 to hw_catalog Vinod Koul
2021-11-16 6:22 ` [PATCH v3 05/13] drm/msm/disp/dpu1: Don't use DSC with mode_3d Vinod Koul
2021-11-24 15:39 ` Dmitry Baryshkov
2021-11-24 15:40 ` Dmitry Baryshkov
2021-11-24 15:57 ` Dmitry Baryshkov
2021-11-24 15:43 ` Dmitry Baryshkov
2021-11-16 6:22 ` [PATCH v3 06/13] drm/msm/disp/dpu1: Add DSC support in hw_ctl Vinod Koul
2021-11-24 15:40 ` Dmitry Baryshkov
2021-11-16 6:22 ` [PATCH v3 07/13] drm/msm/disp/dpu1: Add support for DSC in encoder Vinod Koul
2021-11-24 15:58 ` Dmitry Baryshkov
2021-11-16 6:22 ` [PATCH v3 08/13] drm/msm: Add missing structure documentation Vinod Koul
2021-11-16 6:22 ` [PATCH v3 09/13] drm/msm/disp/dpu1: Add support for DSC in topology Vinod Koul
2021-11-24 15:59 ` Dmitry Baryshkov
2021-11-16 6:22 ` [PATCH v3 10/13] drm/msm/disp/dpu1: Add DSC support in RM Vinod Koul
2021-11-24 16:01 ` Dmitry Baryshkov
2021-11-16 6:22 ` [PATCH v3 11/13] drm/msm/dsi: add mode valid callback for dsi_mgr Vinod Koul
2021-11-24 20:33 ` Dmitry Baryshkov
2021-11-16 6:22 ` [PATCH v3 12/13] drm/msm/dsi: Add support for DSC configuration Vinod Koul
2021-11-18 21:47 ` kernel test robot
2021-11-24 16:21 ` Dmitry Baryshkov
2021-11-24 16:27 ` Dmitry Baryshkov
2021-12-11 0:03 ` Marijn Suijten
2022-02-17 11:14 ` [Freedreno] " Vinod Koul
2022-02-17 15:11 ` Marijn Suijten
2022-03-22 17:16 ` Vinod Koul [this message]
2022-03-22 18:59 ` Marijn Suijten
2022-03-23 10:57 ` Vinod Koul
2021-11-16 6:22 ` [PATCH v3 13/13] drm/msm/dsi: Pass DSC params to drm_panel Vinod Koul
2021-11-24 16:28 ` Dmitry Baryshkov
2021-11-24 16:51 ` Dmitry Baryshkov
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