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    SubjectRe: [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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