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Message-ID: <6e40f885-ef27-bb93-bb97-be25feca29f6@linaro.org>
Date:   Tue, 15 Feb 2022 16:41:29 +0300
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Subject: Re: [PATCH v4 1/2] drm/msm/dp: revise timing engine programming to
 support widebus feature
Content-Language: en-GB
To:     Bjorn Andersson <bjorn.andersson@linaro.org>,
        Kuogee Hsieh <quic_khsieh@quicinc.com>
Cc:     dri-devel@lists.freedesktop.org, robdclark@gmail.com,
        sean@poorly.run, swboyd@chromium.org, vkoul@kernel.org,
        daniel@ffwll.ch, airlied@linux.ie, agross@kernel.org,
        quic_abhinavk@quicinc.com, quic_aravindh@quicinc.com,
        quic_sbillaka@quicinc.com, freedreno@lists.freedesktop.org,
        linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org
References: <1644878346-28511-1-git-send-email-quic_khsieh@quicinc.com>
 <1644878346-28511-2-git-send-email-quic_khsieh@quicinc.com>
 <YgsoOP3DegHz9zA8@yoga>
From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
In-Reply-To: <YgsoOP3DegHz9zA8@yoga>
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Content-Transfer-Encoding: 7bit
Precedence: bulk

On 15/02/2022 07:12, Bjorn Andersson wrote:
> On Mon 14 Feb 16:39 CST 2022, Kuogee Hsieh wrote:
> 
>> Widebus feature will transmit two pixel data per pixel clock to interface.
>> Timing engine provides driving force for this purpose. This patch base
>> on HPG (Hardware Programming Guide) to revise timing engine register
>> setting to accommodate both widebus and non widebus application. Also
>> horizontal width parameters need to be reduced by half since two pixel
>> data are clocked out per pixel clock when widebus feature enabled.
>>
>> Widebus can be enabled individually at DP. However at DSI, widebus have
>> to be enabled along with DSC enabled to achieve pixel clock rate be
>> scaled down with same ratio as compression ratio when 10 bits per source
>> component. Therefore this patch have both widebus and compression covered
>> together so tat less efforts will be required when DSC enabled later.

Please split compression away. It's has hanging loose ends, which are 
not tied anywhere. It can be sent as a part of this patch series, but 
will be merged later, together with the DP DSC support.

In general, sending a patch that does several items at once is not the 
best idea. Usually it's better to send two separate patches.

>>
>> Changes in v2:
>> -- remove compression related code from timing
>> -- remove op_info from  struct msm_drm_private
>> -- remove unnecessary wide_bus_en variables
>> -- pass wide_bus_en into timing configuration by struct msm_dp
>>
>> Changes in v3:
>> -- split patch into 3 patches
>>
>> Changes in v4:
>> -- rework timing engine to not interfere with dsi/hdmi

Thanks a lot, this is much cleaner now!

>> -- cover both widebus and compression
>>
> 
> Even though the change relates to DP, I think it would be appropriate to
> change the $subject prefix to "drm/msm/dpu".
> 
> When booting sc8180x the bootloader leaves widebus enabled in the eDP
> controller, and the two patches takes care of this problem for me. I
> also checked the DP still works.
> 
> Tested-by: Bjorn Andersson <bjorn.andersson@linaro.org>
> 
> Thanks,
> Bjorn
> 
>> Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
>> ---
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c        | 10 +++
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h        |  2 +
>>   .../gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c   | 14 +++
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c        | 99 ++++++++++++++++++----
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.h        |  6 ++
>>   5 files changed, 115 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>> index 0d315b4..0c22839 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>> @@ -208,6 +208,8 @@ struct dpu_encoder_virt {
>>   
>>   	u32 idle_timeout;
>>   
>> +	bool wide_bus_en;
>> +
>>   	struct msm_dp *dp;
>>   };
>>   
>> @@ -217,6 +219,14 @@ static u32 dither_matrix[DITHER_MATRIX_SZ] = {
>>   	15, 7, 13, 5, 3, 11, 1, 9, 12, 4, 14, 6, 0, 8, 2, 10
>>   };
>>   
>> +
>> +bool dpu_encoder_is_widebus_enabled(struct drm_encoder *drm_enc)
>> +{
>> +	struct dpu_encoder_virt *dpu_enc = to_dpu_encoder_virt(drm_enc);
>> +
>> +	return dpu_enc->wide_bus_en;
>> +}
>> +
>>   static void _dpu_encoder_setup_dither(struct dpu_hw_pingpong *hw_pp, unsigned bpc)
>>   {
>>   	struct dpu_hw_dither_cfg dither_cfg = { 0 };
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
>> index 99a5d73..893d74d 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
>> @@ -168,4 +168,6 @@ int dpu_encoder_get_linecount(struct drm_encoder *drm_enc);
>>    */
>>   int dpu_encoder_get_frame_count(struct drm_encoder *drm_enc);
>>   
>> +bool dpu_encoder_is_widebus_enabled(struct drm_encoder *drm_enc);
>> +
>>   #endif /* __DPU_ENCODER_H__ */
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c
>> index 185379b..2af2bb7 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c
>> @@ -110,6 +110,20 @@ static void drm_mode_to_intf_timing_params(
>>   		timing->v_back_porch += timing->v_front_porch;
>>   		timing->v_front_porch = 0;
>>   	}
>> +
>> +	timing->wide_bus_en = dpu_encoder_is_widebus_enabled(phys_enc->parent);
>> +
>> +	/*
>> +	 * for DP, divide the horizonal parameters by 2 when
>> +	 * widebus is enabled
>> +	 */
>> +	if (phys_enc->hw_intf->cap->type == INTF_DP && timing->wide_bus_en) {
>> +		timing->width = timing->width >> 1;
>> +		timing->xres = timing->xres >> 1;
>> +		timing->h_back_porch = timing->h_back_porch >> 1;
>> +		timing->h_front_porch = timing->h_front_porch >> 1;
>> +		timing->hsync_pulse_width = timing->hsync_pulse_width >> 1;
>> +	}
>>   }
>>   
>>   static u32 get_horizontal_total(const struct intf_timing_params *timing)
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c
>> index 116e2b5..3b9273e 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c
>> @@ -33,6 +33,7 @@
>>   #define INTF_TP_COLOR1                  0x05C
>>   #define INTF_CONFIG2                    0x060
>>   #define INTF_DISPLAY_DATA_HCTL          0x064
>> +#define INTF_ACTIVE_DATA_HCTL           0x068
>>   #define INTF_FRAME_LINE_COUNT_EN        0x0A8
>>   #define INTF_FRAME_COUNT                0x0AC
>>   #define   INTF_LINE_COUNT               0x0B0
>> @@ -60,6 +61,14 @@
>>   
>>   #define   INTF_MUX                      0x25C
>>   
>> +#define BIT_INTF_CFG_ACTIVE_H_EN	BIT(29)
>> +#define BIT_INTF_CFG_ACTIVE_V_EN	BIT(30)
>> +
>> +#define BIT_INTF_CFG2_DATABUS_WIDEN	BIT(0)
>> +#define BIT_INTF_CFG2_DATA_HCTL_EN	BIT(4)
>> +#define BIT_INTF_CFG2_DCE_DATA_COMPRESS	BIT(12)

No need to prefix names with BIT_. Other DPU source files do not do this.

>> +
>> +
>>   static const struct dpu_intf_cfg *_intf_offset(enum dpu_intf intf,
>>   		const struct dpu_mdss_cfg *m,
>>   		void __iomem *addr,
>> @@ -90,15 +99,23 @@ static void dpu_hw_intf_setup_timing_engine(struct dpu_hw_intf *ctx,
>>   	u32 hsync_period, vsync_period;
>>   	u32 display_v_start, display_v_end;
>>   	u32 hsync_start_x, hsync_end_x;
>> +	u32 hsync_data_start_x, hsync_data_end_x;
>>   	u32 active_h_start, active_h_end;
>>   	u32 active_v_start, active_v_end;
>>   	u32 active_hctl, display_hctl, hsync_ctl;
>>   	u32 polarity_ctl, den_polarity, hsync_polarity, vsync_polarity;
>>   	u32 panel_format;
>> -	u32 intf_cfg, intf_cfg2 = 0, display_data_hctl = 0;
>> +	u32 intf_cfg, intf_cfg2 = 0;
>> +	u32 display_data_hctl = 0, active_data_hctl = 0;
>> +	u32 data_width;
>> +	bool dp_intf = false;
>>   
>>   	/* read interface_cfg */
>>   	intf_cfg = DPU_REG_READ(c, INTF_CONFIG);
>> +
>> +	if (ctx->cap->type == INTF_EDP || ctx->cap->type == INTF_DP)
>> +		dp_intf = true;
>> +
>>   	hsync_period = p->hsync_pulse_width + p->h_back_porch + p->width +
>>   	p->h_front_porch;
>>   	vsync_period = p->vsync_pulse_width + p->v_back_porch + p->height +
>> @@ -112,7 +129,10 @@ static void dpu_hw_intf_setup_timing_engine(struct dpu_hw_intf *ctx,
>>   	hsync_start_x = p->h_back_porch + p->hsync_pulse_width;
>>   	hsync_end_x = hsync_period - p->h_front_porch - 1;
>>   
>> -	if (p->width != p->xres) {
>> +	hsync_ctl = (hsync_period << 16) | p->hsync_pulse_width;
>> +	display_hctl = (hsync_end_x << 16) | hsync_start_x;
>> +
>> +	if (p->width != p->xres) { /* border fill added */
>>   		active_h_start = hsync_start_x;
>>   		active_h_end = active_h_start + p->xres - 1;
>>   	} else {
>> @@ -130,27 +150,78 @@ static void dpu_hw_intf_setup_timing_engine(struct dpu_hw_intf *ctx,
>>   
>>   	if (active_h_end) {
>>   		active_hctl = (active_h_end << 16) | active_h_start;
>> -		intf_cfg |= BIT(29);	/* ACTIVE_H_ENABLE */
>> +		intf_cfg |= BIT_INTF_CFG_ACTIVE_H_EN;

Such changes can go to a separate patch. You don't have to squash 
everything in a single patch. Quite the opposite. If each of the patches 
is atomic, it's easier to review and accept them.

>>   	} else {
>>   		active_hctl = 0;
>>   	}
>>   
>>   	if (active_v_end)
>> -		intf_cfg |= BIT(30); /* ACTIVE_V_ENABLE */
>> +		intf_cfg |= BIT_INTF_CFG_ACTIVE_V_EN;
>>   
>> -	hsync_ctl = (hsync_period << 16) | p->hsync_pulse_width;
>> -	display_hctl = (hsync_end_x << 16) | hsync_start_x;

Why did you move these assignments?

>> +	/*
>> +	 * DATA_HCTL_EN controls data timing which can be different from
>> +	 * video timing. It is recommended to enable it for all cases, except
>> +	 * if compression is enabled in 1 pixel per clock mode
>> +	 */
>> +	if (!p->compression_en || p->wide_bus_en)
>> +		intf_cfg2 |= BIT_INTF_CFG2_DATA_HCTL_EN;

So, we are enabling it uncoditionally even for older platforms, which do 
not support this bit/register. I'm not a fan of writing to registers 
which are not supported by the hardware.

>> +
>> +	if (p->wide_bus_en)
>> +		intf_cfg2 |=  BIT_INTF_CFG2_DATABUS_WIDEN;
>> +
>> +	/*
>> +	 * If widebus is disabled:
>> +	 * For uncompressed stream, the data is valid for the entire active
>> +	 * window period.
>> +	 * For compressed stream, data is valid for a shorter time period
>> +	 * inside the active window depending on the compression ratio.
>> +	 *
>> +	 * If widebus is enabled:
>> +	 * For uncompressed stream, data is valid for only half the active
>> +	 * window, since the data rate is doubled in this mode.
>> +	 * p->width holds the adjusted width for DP but unadjusted width for DSI
>> +	 * For compressed stream, data validity window needs to be adjusted for
>> +	 * compression ratio and then further halved.
>> +	 */
>> +	data_width = p->width;
>> +
>> +	if (p->compression_en) {
>> +		data_width = DIV_ROUND_UP(p->dce_bytes_per_line, 3);

dce_bytes_per_line is never set.

>> +
>> +		if (p->wide_bus_en)
>> +			data_width >>= 1;
>> +	} else if (!dp_intf && p->wide_bus_en) {
>> +		data_width = p->width >> 1;
>> +	}
>> +
>> +	hsync_data_start_x = hsync_start_x;
>> +	hsync_data_end_x =  hsync_start_x + data_width - 1;
>> +
>> +	display_data_hctl = (hsync_data_end_x << 16) | hsync_data_start_x;
>> +
>> +	if (dp_intf) {
>> +		/* DP timing adjustment */
>> +		display_v_start += p->hsync_pulse_width + p->h_back_porch;
>> +		display_v_end   -= p->h_front_porch;

So, this changes the display_v_end. Is there a mistake currently (and so 
this change should be backported to stable kernels) or is it just unoptimal?

>>   
>> -	if (ctx->cap->type == INTF_EDP || ctx->cap->type == INTF_DP) {
>>   		active_h_start = hsync_start_x;
>>   		active_h_end = active_h_start + p->xres - 1;
>>   		active_v_start = display_v_start;
>>   		active_v_end = active_v_start + (p->yres * hsync_period) - 1;
>>   
>> -		display_v_start += p->hsync_pulse_width + p->h_back_porch;

Another unnnecessary move.

>> -
>>   		active_hctl = (active_h_end << 16) | active_h_start;
>>   		display_hctl = active_hctl;
>> +
>> +		intf_cfg |= BIT_INTF_CFG_ACTIVE_H_EN;
>> +		intf_cfg |= BIT_INTF_CFG_ACTIVE_V_EN;
>> +
>> +		if (p->compression_en) {
>> +			active_data_hctl = (hsync_start_x +
>> +					p->extra_dto_cycles) << 16;

extra_dto_cycles is always unset (0). Is this expected?

>> +			active_data_hctl += hsync_start_x;
>> +
>> +			display_data_hctl = active_data_hctl;
>> +		}
>>   	}
>>   
>>   	den_polarity = 0;
>> @@ -180,13 +251,6 @@ static void dpu_hw_intf_setup_timing_engine(struct dpu_hw_intf *ctx,
>>   				(COLOR_8BIT << 4) |
>>   				(0x21 << 8));
>>   
>> -	if (ctx->cap->features & BIT(DPU_DATA_HCTL_EN)) {

If you insist on always programming these registers, the 
DPU_DATA_HCTL_EN becomes useless and should be removed from the 
dpu_hw_catalog. As usual, in a separate patch.

>> -		intf_cfg2 |= BIT(4);
>> -		display_data_hctl = display_hctl;
>> -		DPU_REG_WRITE(c, INTF_CONFIG2, intf_cfg2);
>> -		DPU_REG_WRITE(c, INTF_DISPLAY_DATA_HCTL, display_data_hctl);
>> -	}
>> -
>>   	DPU_REG_WRITE(c, INTF_HSYNC_CTL, hsync_ctl);
>>   	DPU_REG_WRITE(c, INTF_VSYNC_PERIOD_F0, vsync_period * hsync_period);
>>   	DPU_REG_WRITE(c, INTF_VSYNC_PULSE_WIDTH_F0,
>> @@ -204,6 +268,9 @@ static void dpu_hw_intf_setup_timing_engine(struct dpu_hw_intf *ctx,
>>   	DPU_REG_WRITE(c, INTF_FRAME_LINE_COUNT_EN, 0x3);
>>   	DPU_REG_WRITE(c, INTF_CONFIG, intf_cfg);
>>   	DPU_REG_WRITE(c, INTF_PANEL_FORMAT, panel_format);
>> +	DPU_REG_WRITE(c, INTF_CONFIG2, intf_cfg2);
>> +	DPU_REG_WRITE(c, INTF_DISPLAY_DATA_HCTL, display_data_hctl);
>> +	DPU_REG_WRITE(c, INTF_ACTIVE_DATA_HCTL, active_data_hctl);
>>   }
>>   
>>   static void dpu_hw_intf_enable_timing_engine(
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.h
>> index 3568be8..299c9c1 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.h
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.h
>> @@ -30,6 +30,12 @@ struct intf_timing_params {
>>   	u32 border_clr;
>>   	u32 underflow_clr;
>>   	u32 hsync_skew;
>> +
>> +	bool wide_bus_en;
>> +	bool compression_en;
>> +	u32 extra_dto_cycles;   /* for DP only */

Never set, so it's equal to 0

>> +	bool dsc_4hs_merge;     /* DSC 4HS merge */

Unused

>> +	u32 dce_bytes_per_line;

Never set, so it's equal to 0

>>   };
>>   
>>   struct intf_prog_fetch {
>> -- 
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
>> a Linux Foundation Collaborative Project
>>


-- 
With best wishes
Dmitry