Re: [PATCH v5] drm/mediatek: fixed the calc method of data rate per lane

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Hi Jitao,

On Wed, Nov 16, 2016 at 11:20 AM, Jitao Shi <jitao.shi@xxxxxxxxxxxx> wrote:
>
> Tune dsi frame rate by pixel clock, dsi add some extra signal (i.e.
> Tlpx, Ths-prepare, Ths-zero, Ths-trail,Ths-exit) when enter and exit LP
> mode, those signals will cause h-time larger than normal and reduce FPS.
> So need to multiply a coefficient to offset the extra signal's effect.
>   coefficient = ((htotal*bpp/lane_number)+Tlpx+Ths_prep+Ths_zero+
>                  Ths_trail+Ths_exit)/(htotal*bpp/lane_number)
>
> Signed-off-by: Jitao Shi <jitao.shi@xxxxxxxxxxxx>

For this patch,
Reviewed-by: Daniel Kurtz <djkurtz@xxxxxxxxxxxx>

But, one more clean up suggestion for another patch, below...

> ---
> Change since v4:
>  - tune the calc comment more clear.
>  - define the phy timings as constants.
>
> Chnage since v3:
>  - wrapp the commit msg.
>  - fix alignment of some lines.
>
> Change since v2:
>  - move phy timing back to dsi_phy_timconfig.
>
> Change since v1:
>  - phy_timing2 and phy_timing3 refer clock cycle time.
>  - define values of LPX HS_PRPR HS_ZERO HS_TRAIL TA_GO TA_SURE TA_GET DA_HS_EXIT.
> ---
>  drivers/gpu/drm/mediatek/mtk_dsi.c |   64 +++++++++++++++++++++++++++---------
>  1 file changed, 48 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index 28b2044..eaa5a22 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -86,7 +86,7 @@
>
>  #define DSI_PHY_TIMECON0       0x110
>  #define LPX                            (0xff << 0)
> -#define HS_PRPR                                (0xff << 8)
> +#define HS_PREP                                (0xff << 8)
>  #define HS_ZERO                                (0xff << 16)
>  #define HS_TRAIL                       (0xff << 24)
>
> @@ -102,10 +102,16 @@
>  #define CLK_TRAIL                      (0xff << 24)
>
>  #define DSI_PHY_TIMECON3       0x11c
> -#define CLK_HS_PRPR                    (0xff << 0)
> +#define CLK_HS_PREP                    (0xff << 0)
>  #define CLK_HS_POST                    (0xff << 8)
>  #define CLK_HS_EXIT                    (0xff << 16)
>
> +#define T_LPX          5
> +#define T_HS_PREP      6
> +#define T_HS_TRAIL     8
> +#define T_HS_EXIT      7
> +#define T_HS_ZERO      10
> +
>  #define NS_TO_CYCLE(n, c)    ((n) / (c) + (((n) % (c)) ? 1 : 0))
>
>  struct phy;
> @@ -161,20 +167,18 @@ static void mtk_dsi_mask(struct mtk_dsi *dsi, u32 offset, u32 mask, u32 data)
>  static void dsi_phy_timconfig(struct mtk_dsi *dsi)
>  {
>         u32 timcon0, timcon1, timcon2, timcon3;
> -       unsigned int ui, cycle_time;
> -       unsigned int lpx;
> +       u32 ui, cycle_time;
>
>         ui = 1000 / dsi->data_rate + 0x01;
>         cycle_time = 8000 / dsi->data_rate + 0x01;
> -       lpx = 5;
>
> -       timcon0 = (8 << 24) | (0xa << 16) | (0x6 << 8) | lpx;
> -       timcon1 = (7 << 24) | (5 * lpx << 16) | ((3 * lpx) / 2) << 8 |
> -                 (4 * lpx);
> +       timcon0 = T_LPX | T_HS_PREP << 8 | T_HS_ZERO << 16 | T_HS_TRAIL << 24;
> +       timcon1 = 4 * T_LPX | (3 * T_LPX / 2) << 8 | 5 * T_LPX << 16 |
> +                 T_HS_EXIT << 24;
>         timcon2 = ((NS_TO_CYCLE(0x64, cycle_time) + 0xa) << 24) |
>                   (NS_TO_CYCLE(0x150, cycle_time) << 16);
> -       timcon3 = (2 * lpx) << 16 | NS_TO_CYCLE(80 + 52 * ui, cycle_time) << 8 |
> -                  NS_TO_CYCLE(0x40, cycle_time);
> +       timcon3 = NS_TO_CYCLE(0x40, cycle_time) | (2 * T_LPX) << 16 |
> +                 NS_TO_CYCLE(80 + 52 * ui, cycle_time) << 8;
>
>         writel(timcon0, dsi->regs + DSI_PHY_TIMECON0);
>         writel(timcon1, dsi->regs + DSI_PHY_TIMECON1);
> @@ -202,19 +206,47 @@ static int mtk_dsi_poweron(struct mtk_dsi *dsi)
>  {
>         struct device *dev = dsi->dev;
>         int ret;
> +       u64 pixel_clock, total_bits;
> +       u32 htotal, htotal_bits, bit_per_pixel, overhead_cycles, overhead_bits;
>
>         if (++dsi->refcount != 1)
>                 return 0;
>
> +       switch (dsi->format) {
> +       case MIPI_DSI_FMT_RGB565:
> +               bit_per_pixel = 16;
> +               break;
> +       case MIPI_DSI_FMT_RGB666_PACKED:
> +               bit_per_pixel = 18;
> +               break;
> +       case MIPI_DSI_FMT_RGB666:
> +       case MIPI_DSI_FMT_RGB888:
> +       default:
> +               bit_per_pixel = 24;
> +               break;
> +       }
> +
>         /**
> -        * data_rate = (pixel_clock / 1000) * pixel_dipth * mipi_ratio;
> -        * pixel_clock unit is Khz, data_rata unit is MHz, so need divide 1000.
> -        * mipi_ratio is mipi clk coefficient for balance the pixel clk in mipi.
> -        * we set mipi_ratio is 1.05.
> +        * vm.pixelclock is in kHz, pixel_clock unit is Hz, so multiply by 1000
> +        * htotal_time = htotal * byte_per_pixel / num_lanes
> +        * overhead_time = lpx + hs_prepare + hs_zero + hs_trail + hs_exit
> +        * mipi_ratio = (htotal_time + overhead_time) / htotal_time
> +        * data_rate = pixel_clock * bit_per_pixel * mipi_ratio / num_lanes;
>          */
> -       dsi->data_rate = dsi->vm.pixelclock * 3 * 21 / (1 * 1000 * 10);
> +       pixel_clock = dsi->vm.pixelclock * 1000;
> +       htotal = dsi->vm.hactive + dsi->vm.hback_porch + dsi->vm.hfront_porch +
> +                       dsi->vm.hsync_len;
> +       htotal_bits = htotal * bit_per_pixel;
> +
> +       overhead_cycles = T_LPX + T_HS_PREP + T_HS_ZERO + T_HS_TRAIL +
> +                       T_HS_EXIT;
> +       overhead_bits = overhead_cycles * dsi->lanes * 8;
> +       total_bits = htotal_bits + overhead_bits;
> +
> +       dsi->data_rate = DIV_ROUND_UP_ULL(pixel_clock * total_bits,
> +                                         htotal * dsi->lanes);

dsi->data_rate is only used here and in dsi_phy_timconfig(), which is
called directly a few lines down in this same function.
Rather than permanently storing this as state in struct mtk_dsi, just
pass the newly computed data_rate as a paratmer to
dsi_phy_timconfig().

Thanks,
-Dan

>
> -       ret = clk_set_rate(dsi->hs_clk, dsi->data_rate * 1000000);
> +       ret = clk_set_rate(dsi->hs_clk, dsi->data_rate);
>         if (ret < 0) {
>                 dev_err(dev, "Failed to set data rate: %d\n", ret);
>                 goto err_refcount;
> --
> 1.7.9.5
>
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