Re: drm/mediatek: fixed the calc method of data rate per lane

[CK Hu]

Hi, Jitao:

Sorry for late reply.
Some comments inline.

On Fri, 2016-08-26 at 14:10 +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))
> 
> Signed-off-by: Jitao Shi <jitao.shi@xxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/mediatek/mtk_dsi.c |  111 ++++++++++++++++++++++--------------
>  1 file changed, 67 insertions(+), 44 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index 28b2044..506aa22 100644

[snip...]

>  
> -static void dsi_phy_timconfig(struct mtk_dsi *dsi)
> +static void dsi_phy_timconfig(struct mtk_dsi *dsi, u32 phy_timing0,
> +			      u32 phy_timing1, u32 phy_timing2,
> +			      u32 phy_timing3)
>  {
> -	u32 timcon0, timcon1, timcon2, timcon3;
> -	unsigned int ui, cycle_time;
> -	unsigned int lpx;
> -
> -	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);
> -	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);
> -
> -	writel(timcon0, dsi->regs + DSI_PHY_TIMECON0);
> -	writel(timcon1, dsi->regs + DSI_PHY_TIMECON1);
> -	writel(timcon2, dsi->regs + DSI_PHY_TIMECON2);
> -	writel(timcon3, dsi->regs + DSI_PHY_TIMECON3);
> +	writel(phy_timing0, dsi->regs + DSI_PHY_TIMECON0);
> +	writel(phy_timing1, dsi->regs + DSI_PHY_TIMECON1);
> +	writel(phy_timing2, dsi->regs + DSI_PHY_TIMECON2);
> +	writel(phy_timing3, dsi->regs + DSI_PHY_TIMECON3);
>  }
>  
>  static void mtk_dsi_enable(struct mtk_dsi *dsi)
> @@ -202,19 +186,57 @@ 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;
> +	u32 phy_timing0, phy_timing1, phy_timing2, phy_timing3;
>  
>  	if (++dsi->refcount != 1)
>  		return 0;
>  
> +	phy_timing0 = LPX(5) | HS_PRPR(6) | HS_ZERO(10) | HS_TRAIL(8);
> +	phy_timing1 = TA_GO(20) | TA_SURE(7) | TA_GET(25) | DA_HS_EXIT(7);
> +	phy_timing2 = CLK_ZERO(38) | CLK_TRAIL(22);
> +	phy_timing3 = CLK_HS_PRPR(8) | CLK_HS_POST(21) | CLK_HS_EXIT(10);

The original phy_timing2 and phy_timing3 is defined as

	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);

They are varied by cycle_time. I think you should not use a fixed value
for them.

> +
> +	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 = (phy_timing0 & 0xff) + (phy_timing0 >> 8 & 0xff) +
> +			  (phy_timing0 >> 16 & 0xff) +
> +			  (phy_timing0 >> 24 & 0xff) +
> +			  (phy_timing1 >> 24 & 0xff);

I think phy_timing0 and phy_timing1 is defined as

	phy_timing0 = LPX(a) | HS_PRPR(b) | HS_ZERO(c) | HS_TRAIL(d);
	phy_timing1 = TA_GO(e) | TA_SURE(f) | TA_GET(g) | DA_HS_EXIT(h);

So, it could be a more simple way to assign overhead_cycles like this

	overhead_cycles = a + b + c + d + h;

Because these variable are constant, maybe you can define them as
symbols.


> +	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;
> @@ -236,7 +258,8 @@ static int mtk_dsi_poweron(struct mtk_dsi *dsi)
>  
>  	mtk_dsi_enable(dsi);
>  	mtk_dsi_reset(dsi);
> -	dsi_phy_timconfig(dsi);
> +	dsi_phy_timconfig(dsi, phy_timing0, phy_timing1, phy_timing2,
> +			  phy_timing3);
>  
>  	return 0;
>  

Regards,
CK