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Date: Thu, 17 Feb 2022 16:44:04 +0530
From: Vinod Koul <vkoul@...nel.org>
To: Marijn Suijten <marijn.suijten@...ainline.org>
Cc: Jonathan Marek <jonathan@...ek.ca>,
Jeffrey Hugo <jeffrey.l.hugo@...il.com>,
David Airlie <airlied@...ux.ie>, linux-arm-msm@...r.kernel.org,
Konrad Dybcio <konrad.dybcio@...ainline.org>,
linux-kernel@...r.kernel.org,
Abhinav Kumar <abhinavk@...eaurora.org>,
Bjorn Andersson <bjorn.andersson@...aro.org>,
Rob Clark <robdclark@...il.com>,
dri-devel@...ts.freedesktop.org, Daniel Vetter <daniel@...ll.ch>,
Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
freedreno@...ts.freedesktop.org,
Sumit Semwal <sumit.semwal@...aro.org>
Subject: Re: [Freedreno] [PATCH v3 12/13] drm/msm/dsi: Add support for DSC
configuration
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...
>
> > +{
> > + 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);
> > + DBG("Mode Width- %d x Height %d\n", dsc->drm->pic_width, dsc->drm->pic_height);
>
> This seems to be pretty non-standard and perhaps unnecessary debug code,
> with a stray dash in there. Is is needed here, and if so how about
> using %dx%d\n to format width and height?
I can update that, sure...
>
> > +
> > + /* 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...
>
> > + h_total -= hdisplay;
> > + hdisplay /= 3;
> > + h_total += hdisplay;
> > + ha_end = ha_start + hdisplay;
> > + }
> > +
> > if (msm_host->mode_flags & MIPI_DSI_MODE_VIDEO) {
> > + if (msm_host->dsc) {
> > + struct msm_display_dsc_config *dsc = msm_host->dsc;
> > + u32 reg, intf_width, slice_per_intf;
> > + u32 total_bytes_per_intf;
> > +
> > + /* first calculate dsc parameters and then program
> > + * compress mode registers
> > + */
> > + intf_width = hdisplay;
> > + slice_per_intf = DIV_ROUND_UP(intf_width, dsc->drm->slice_width);
> > +
> > + dsc->drm->slice_count = 1;
> > + dsc->bytes_in_slice = DIV_ROUND_UP(dsc->drm->slice_width * 8, 8);
>
> If I am not mistaken this is the same value as dsc->drm->slice_width,
> since a multiple of 8 is inherently "a multiple of 8" and hence needs no
> rounding when divided by 8 again.
Yes this doesnt look right, I will update
> Also note that the cmdmode variant below uses bits_per_pixel here; is
> that discrepancy intended?
Nope both should use bits_per_pixel..
> > + total_bytes_per_intf = dsc->bytes_in_slice * slice_per_intf;
> > +
> > + dsc->eol_byte_num = total_bytes_per_intf % 3;
> > + dsc->pclk_per_line = DIV_ROUND_UP(total_bytes_per_intf, 3);
> > + dsc->bytes_per_pkt = dsc->bytes_in_slice * dsc->drm->slice_count;
> > + dsc->pkt_per_line = slice_per_intf / dsc->drm->slice_count;
> > +
> > + reg = dsc->bytes_per_pkt << 16;
> > + reg |= (0x0b << 8); /* dtype of compressed image */
> > +
> > + /* pkt_per_line:
> > + * 0 == 1 pkt
> > + * 1 == 2 pkt
> > + * 2 == 4 pkt
> > + * 3 pkt is not supported
> > + * above translates to ffs() - 1
> > + */
> > + reg |= (ffs(dsc->pkt_per_line) - 1) << 6;
> > +
> > + dsc->eol_byte_num = total_bytes_per_intf % 3;
>
> This was already calculated and assigned just a couple lines above.
Yup, dropped now.
>
> > + reg |= dsc->eol_byte_num << 4;
> > + reg |= 1;
>
> Note that the XML register file exists to map out the layout of these
> registers, including bit offset, size, and (enum) constant values. It
> is appreciated if you can replace all these magical shifts and magic
> flags/bits with the appropriate enum constants and constructor
> functions, after mapping them out in the XML file.
Yeah I am trying to get those details, if I manage to get it, will
update for sure as Dmitry already pointed in MESA PR.
> > +
> > + dsi_write(msm_host,
> > + REG_DSI_VIDEO_COMPRESSION_MODE_CTRL, reg);
> > + }
> > +
> > dsi_write(msm_host, REG_DSI_ACTIVE_H,
> > DSI_ACTIVE_H_START(ha_start) |
> > DSI_ACTIVE_H_END(ha_end));
> > @@ -959,8 +1034,40 @@ static void dsi_timing_setup(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
> > DSI_ACTIVE_VSYNC_VPOS_START(vs_start) |
> > DSI_ACTIVE_VSYNC_VPOS_END(vs_end));
> > } else { /* command mode */
> > + 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
> > +
> > + slice_per_intf = DIV_ROUND_UP(hdisplay, dsc->drm->slice_width);
> > + bytes_in_slice = DIV_ROUND_UP(dsc->drm->slice_width *
> > + dsc->drm->bits_per_pixel, 8);
> > + dsc->drm->slice_chunk_size = bytes_in_slice;
> > + total_bytes_per_intf = dsc->bytes_in_slice * slice_per_intf;
> > + dsc->pkt_per_line = slice_per_intf / dsc->drm->slice_count;
> > +
> > + reg = 0x39 << 8;
>
> Same comment about moving magic constants and shifts into the XML file.
yes if we get details of bits
>
> > + reg |= ffs(dsc->pkt_per_line) << 6;
>
> Doesn't the calculation need -1 here just like video mode?
yes will update now
--
~Vinod
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