Re: [PATCH v3] drm/mediatek: fixed the calc method of data rate per lane

From: CK Hu
Date: Wed Oct 26 2016 - 05:38:16 EST


Hi, Jitao:

On Wed, 2016-10-26 at 16:59 +0800, Jitao Shi 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, this
> signal will cause h-time larger than normal and reduce FPS.
> 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))
>

One check-patch warning in commit message:

WARNING:COMMIT_LOG_LONG_LINE: Possible unwrapped commit description
(prefer a maximum 75 chars per line)
#7:
Tune dsi frame rate by pixel clock, dsi add some extra signal (i.e.
Tlpx,

> Signed-off-by: Jitao Shi <jitao.shi@xxxxxxxxxxxx>
> ---
> 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 | 74 +++++++++++++++++++++++++-----------
> 1 file changed, 51 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index 28b2044..8b3b38a 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -85,16 +85,16 @@
> #define LD0_WAKEUP_EN BIT(2)
>
> #define DSI_PHY_TIMECON0 0x110
> -#define LPX (0xff << 0)
> -#define HS_PRPR (0xff << 8)
> -#define HS_ZERO (0xff << 16)
> -#define HS_TRAIL (0xff << 24)
> +#define LPX (5 << 0)
> +#define HS_PRPR (6 << 8)
> +#define HS_ZERO (10 << 16)
> +#define HS_TRAIL (8 << 24)
>
> #define DSI_PHY_TIMECON1 0x114
> -#define TA_GO (0xff << 0)
> -#define TA_SURE (0xff << 8)
> -#define TA_GET (0xff << 16)
> -#define DA_HS_EXIT (0xff << 24)
> +#define TA_GO (20 << 0)
> +#define TA_SURE (7 << 8)
> +#define TA_GET (25 << 16)
> +#define DA_HS_EXIT (7 << 24)
>
> #define DSI_PHY_TIMECON2 0x118
> #define CONT_DET (0xff << 0)
> @@ -161,20 +161,18 @@ 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 = LPX | HS_PRPR | HS_ZERO | HS_TRAIL;
> + timcon1 = 4 * LPX | (3 * LPX / 2) << 8 | 5 * LPX << 16 | DA_HS_EXIT;
> 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);
> + (NS_TO_CYCLE(0x150, cycle_time) << 16);

I think this line may align to '(' in the right of '='.

> + timcon3 = (2 * LPX) << 16 |
> + NS_TO_CYCLE(80 + 52 * ui, cycle_time) << 8 |
> + NS_TO_CYCLE(0x40, cycle_time);

I think these two lines may align to '(' in the right of '='.

Regards,
CK
I.
>
> writel(timcon0, dsi->regs + DSI_PHY_TIMECON0);
> writel(timcon1, dsi->regs + DSI_PHY_TIMECON1);
> @@ -202,19 +200,49 @@ static int mtk_dsi_poweron(struct mtk_dsi *dsi)
> {
> struct device *dev = dsi->dev;
> int ret;
> + u64 bit_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.
> + * data_rate = (pixel_clock) * bit_per_pixel * mipi_ratio / lane_num;
> + * vm.pixelclock is Khz, data_rata unit is Hz, so need to multiply 1000
> + * mipi_ratio is (htotal * byte_per_pixel / lane_num + Tlpx + Ths_prep
> + * + Thstrail + Ths_exit + Ths_zero) /
> + * (htotal * byte_per_pixel /lane_number)
> */
> - dsi->data_rate = dsi->vm.pixelclock * 3 * 21 / (1 * 1000 * 10);
> + bit_clock = dsi->vm.pixelclock * 1000 * bit_per_pixel;
> + htotal = dsi->vm.hactive + dsi->vm.hback_porch + dsi->vm.hfront_porch +
> + dsi->vm.hsync_len;
> + htotal_bits = htotal * bit_per_pixel;
> +
> + /**
> + * overhead = lpx + hs_prepare + hs_zero + hs_trail + hs_exit
> + */
> + overhead_cycles = LPX + (HS_PRPR >> 8) + (HS_ZERO >> 16) +
> + (HS_TRAIL >> 24) + (DA_HS_EXIT >> 24);
> + overhead_bits = overhead_cycles * dsi->lanes * 8;
> + total_bits = htotal_bits + overhead_bits;
> +
> + dsi->data_rate = DIV_ROUND_UP_ULL(bit_clock * total_bits,
> + htotal_bits * dsi->lanes);
>
> - 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;