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Date:   Fri, 22 Mar 2019 12:19:41 +0200
From:   Tomi Valkeinen <tomi.valkeinen@...com>
To:     Andrey Smirnov <andrew.smirnov@...il.com>,
        <dri-devel@...ts.freedesktop.org>
CC:     Archit Taneja <architt@...eaurora.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Andrey Gusakov <andrey.gusakov@...entembedded.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Chris Healy <cphealy@...il.com>,
        Lucas Stach <l.stach@...gutronix.de>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 04/15] drm/bridge: tc358767: Simplify
 tc_set_video_mode()

On 22/03/2019 05:28, Andrey Smirnov wrote:
> Simplify tc_set_video_mode() by replacing repreated calls to
> tc_write()/regmap_write() with a single call to
> regmap_multi_reg_write(). While at it, simplify explicit shifting by
> using macros from <linux/bitfield.h>. No functional change intended.
> 
> Signed-off-by: Andrey Smirnov <andrew.smirnov@...il.com>
> Cc: Archit Taneja <architt@...eaurora.org>
> Cc: Andrzej Hajda <a.hajda@...sung.com>
> Cc: Laurent Pinchart <Laurent.pinchart@...asonboard.com>
> Cc: Tomi Valkeinen <tomi.valkeinen@...com>
> Cc: Andrey Gusakov <andrey.gusakov@...entembedded.com>
> Cc: Philipp Zabel <p.zabel@...gutronix.de>
> Cc: Chris Healy <cphealy@...il.com>
> Cc: Lucas Stach <l.stach@...gutronix.de>
> Cc: dri-devel@...ts.freedesktop.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  drivers/gpu/drm/bridge/tc358767.c | 146 +++++++++++++++++-------------
>  1 file changed, 85 insertions(+), 61 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c
> index 38d542f553cd..d99c9f32a133 100644
> --- a/drivers/gpu/drm/bridge/tc358767.c
> +++ b/drivers/gpu/drm/bridge/tc358767.c
> @@ -24,6 +24,7 @@
>   * GNU General Public License for more details.
>   */
>  
> +#include <linux/bitfield.h>
>  #include <linux/clk.h>
>  #include <linux/device.h>
>  #include <linux/gpio/consumer.h>
> @@ -56,6 +57,7 @@
>  
>  /* Video Path */
>  #define VPCTRL0			0x0450
> +#define VSDELAY			GENMASK(31, 20)
>  #define OPXLFMT_RGB666			(0 << 8)
>  #define OPXLFMT_RGB888			(1 << 8)
>  #define FRMSYNC_DISABLED		(0 << 4) /* Video Timing Gen Disabled */
> @@ -63,9 +65,17 @@
>  #define MSF_DISABLED			(0 << 0) /* Magic Square FRC disabled */
>  #define MSF_ENABLED			(1 << 0) /* Magic Square FRC enabled */
>  #define HTIM01			0x0454
> +#define HPW			GENMASK(8, 0)
> +#define HBPR			GENMASK(24, 16)
>  #define HTIM02			0x0458
> +#define HDISPR			GENMASK(10, 0)
> +#define HFPR			GENMASK(24, 16)
>  #define VTIM01			0x045c
> +#define VSPR			GENMASK(7, 0)
> +#define VBPR			GENMASK(23, 16)
>  #define VTIM02			0x0460
> +#define VFPR			GENMASK(23, 16)
> +#define VDISPR			GENMASK(10, 0)
>  #define VFUEN0			0x0464
>  #define VFUEN				BIT(0)   /* Video Frame Timing Upload */
>  
> @@ -100,14 +110,28 @@
>  /* Main Channel */
>  #define DP0_SECSAMPLE		0x0640
>  #define DP0_VIDSYNCDELAY	0x0644
> +#define VID_SYNC_DLY		GENMASK(15, 0)
> +#define THRESH_DLY		GENMASK(31, 16)
> +
>  #define DP0_TOTALVAL		0x0648
> +#define H_TOTAL			GENMASK(15, 0)
> +#define V_TOTAL			GENMASK(31, 16)
>  #define DP0_STARTVAL		0x064c
> +#define H_START			GENMASK(15, 0)
> +#define V_START			GENMASK(31, 16)
>  #define DP0_ACTIVEVAL		0x0650
> +#define H_ACT			GENMASK(15, 0)
> +#define V_ACT			GENMASK(31, 16)
> +
>  #define DP0_SYNCVAL		0x0654
> +#define VS_WIDTH		GENMASK(30, 16)
> +#define HS_WIDTH		GENMASK(14, 0)
>  #define SYNCVAL_HS_POL_ACTIVE_LOW	(1 << 15)
>  #define SYNCVAL_VS_POL_ACTIVE_LOW	(1 << 31)
>  #define DP0_MISC		0x0658
>  #define TU_SIZE_RECOMMENDED		(63) /* LSCLK cycles per TU */
> +#define MAX_TU_SYMBOL		GENMASK(28, 23)
> +#define TU_SIZE			GENMASK(21, 16)
>  #define BPC_6				(0 << 5)
>  #define BPC_8				(1 << 5)
>  
> @@ -184,6 +208,12 @@
>  
>  /* Test & Debug */
>  #define TSTCTL			0x0a00
> +#define COLOR_R			GENMASK(31, 24)
> +#define COLOR_G			GENMASK(23, 16)
> +#define COLOR_B			GENMASK(15, 8)
> +#define ENI2CFILTER		BIT(4)
> +#define COLOR_BAR_MODE		GENMASK(1, 0)
> +#define COLOR_BAR_MODE_BARS	2
>  #define PLL_DBG			0x0a04
>  
>  static bool tc_test_pattern;
> @@ -647,10 +677,6 @@ static int tc_get_display_props(struct tc_data *tc)
>  
>  static int tc_set_video_mode(struct tc_data *tc, struct drm_display_mode *mode)
>  {
> -	int ret;
> -	int vid_sync_dly;
> -	int max_tu_symbol;
> -
>  	int left_margin = mode->htotal - mode->hsync_end;
>  	int right_margin = mode->hsync_start - mode->hdisplay;
>  	int hsync_len = mode->hsync_end - mode->hsync_start;
> @@ -659,76 +685,74 @@ static int tc_set_video_mode(struct tc_data *tc, struct drm_display_mode *mode)
>  	int vsync_len = mode->vsync_end - mode->vsync_start;
>  
>  	/*
> -	 * Recommended maximum number of symbols transferred in a transfer unit:
> +	 * Recommended maximum number of symbols transferred in a
> +	 * transfer unit:
>  	 * DIV_ROUND_UP((input active video bandwidth in bytes) * tu_size,
>  	 *              (output active video bandwidth in bytes))
>  	 * Must be less than tu_size.
>  	 */
> -	max_tu_symbol = TU_SIZE_RECOMMENDED - 1;
> -
> -	dev_dbg(tc->dev, "set mode %dx%d\n",
> -		mode->hdisplay, mode->vdisplay);
> -	dev_dbg(tc->dev, "H margin %d,%d sync %d\n",
> -		left_margin, right_margin, hsync_len);
> -	dev_dbg(tc->dev, "V margin %d,%d sync %d\n",
> -		upper_margin, lower_margin, vsync_len);
> -	dev_dbg(tc->dev, "total: %dx%d\n", mode->htotal, mode->vtotal);
> -
> +	int max_tu_symbol = TU_SIZE_RECOMMENDED - 1;
>  
> +	/* DP Main Stream Attributes */
> +	int vid_sync_dly = hsync_len + left_margin + mode->hdisplay;
>  	/*
>  	 * LCD Ctl Frame Size
>  	 * datasheet is not clear of vsdelay in case of DPI
>  	 * assume we do not need any delay when DPI is a source of
>  	 * sync signals
>  	 */
> -	tc_write(VPCTRL0, (0 << 20) /* VSDELAY */ |
> -		 OPXLFMT_RGB888 | FRMSYNC_DISABLED | MSF_DISABLED);
> -	tc_write(HTIM01, (ALIGN(left_margin, 2) << 16) | /* H back porch */
> -			 (ALIGN(hsync_len, 2) << 0));	 /* Hsync */
> -	tc_write(HTIM02, (ALIGN(right_margin, 2) << 16) |  /* H front porch */
> -			 (ALIGN(mode->hdisplay, 2) << 0)); /* width */
> -	tc_write(VTIM01, (upper_margin << 16) |		/* V back porch */
> -			 (vsync_len << 0));		/* Vsync */
> -	tc_write(VTIM02, (lower_margin << 16) |		/* V front porch */
> -			 (mode->vdisplay << 0));	/* height */
> -	tc_write(VFUEN0, VFUEN);		/* update settings */
> -
> -	/* Test pattern settings */
> -	tc_write(TSTCTL,
> -		 (120 << 24) |	/* Red Color component value */
> -		 (20 << 16) |	/* Green Color component value */
> -		 (99 << 8) |	/* Blue Color component value */
> -		 (1 << 4) |	/* Enable I2C Filter */
> -		 (2 << 0) |	/* Color bar Mode */
> -		 0);
> -
> -	/* DP Main Stream Attributes */
> -	vid_sync_dly = hsync_len + left_margin + mode->hdisplay;
> -	tc_write(DP0_VIDSYNCDELAY,
> -		 (max_tu_symbol << 16) |	/* thresh_dly */
> -		 (vid_sync_dly << 0));
> +	const u32 vs_pol = mode->flags & DRM_MODE_FLAG_NVSYNC ?
> +		SYNCVAL_VS_POL_ACTIVE_LOW : 0;
> +	const u32 hs_pol = mode->flags & DRM_MODE_FLAG_NHSYNC ?
> +		SYNCVAL_HS_POL_ACTIVE_LOW : 0;
> +	const struct reg_sequence video_mode_settings[] = {
> +		{ VPCTRL0, FIELD_PREP(VSDELAY, 0) |
> +			   OPXLFMT_RGB888 | FRMSYNC_DISABLED | MSF_DISABLED },
> +		{ HTIM01, FIELD_PREP(HBPR, ALIGN(left_margin, 2)) |
> +			  FIELD_PREP(HPW, ALIGN(hsync_len, 2)) },
> +		{ HTIM02, FIELD_PREP(HDISPR, ALIGN(mode->hdisplay, 2)) |
> +			  FIELD_PREP(HFPR, ALIGN(right_margin, 2)) },
> +		{ VTIM01, FIELD_PREP(VBPR, upper_margin) |
> +			  FIELD_PREP(VSPR, vsync_len) },
> +		{ VTIM02, FIELD_PREP(VFPR, lower_margin) |
> +			  FIELD_PREP(VDISPR, mode->vdisplay) },
> +		{ VFUEN0, VFUEN },
> +		{ TSTCTL, FIELD_PREP(COLOR_R, 120) |
> +			  FIELD_PREP(COLOR_G, 20) |
> +			  FIELD_PREP(COLOR_B, 99) |
> +			  ENI2CFILTER |
> +			  FIELD_PREP(COLOR_BAR_MODE, COLOR_BAR_MODE_BARS) },
> +		{ DP0_VIDSYNCDELAY, FIELD_PREP(THRESH_DLY, max_tu_symbol) |
> +				    FIELD_PREP(VID_SYNC_DLY, vid_sync_dly) },
> +		{ DP0_TOTALVAL, FIELD_PREP(H_TOTAL, mode->htotal) |
> +				FIELD_PREP(V_TOTAL, mode->vtotal) },
> +		{ DP0_STARTVAL, FIELD_PREP(H_START, left_margin + hsync_len) |
> +				FIELD_PREP(V_START,
> +					   upper_margin + vsync_len) },
> +		{ DP0_ACTIVEVAL, FIELD_PREP(V_ACT, mode->vdisplay) |
> +				 FIELD_PREP(H_ACT, mode->hdisplay) },
> +		{ DP0_SYNCVAL, FIELD_PREP(VS_WIDTH, vsync_len) |
> +			       FIELD_PREP(HS_WIDTH, hsync_len) |
> +			       hs_pol | vs_pol },
> +		{ DPIPXLFMT, VS_POL_ACTIVE_LOW | HS_POL_ACTIVE_LOW |
> +			     DE_POL_ACTIVE_HIGH | SUB_CFG_TYPE_CONFIG1 |
> +			     DPI_BPP_RGB888 },
> +		{ DP0_MISC, FIELD_PREP(MAX_TU_SYMBOL, max_tu_symbol) |
> +			    FIELD_PREP(TU_SIZE, TU_SIZE_RECOMMENDED) |
> +			    BPC_8 },
> +	};
>  
> -	tc_write(DP0_TOTALVAL, (mode->vtotal << 16) | (mode->htotal));
> -
> -	tc_write(DP0_STARTVAL,
> -		 ((upper_margin + vsync_len) << 16) |
> -		 ((left_margin + hsync_len) << 0));
> -
> -	tc_write(DP0_ACTIVEVAL, (mode->vdisplay << 16) | (mode->hdisplay));
> -
> -	tc_write(DP0_SYNCVAL, (vsync_len << 16) | (hsync_len << 0) |
> -		 ((mode->flags & DRM_MODE_FLAG_NHSYNC) ? SYNCVAL_HS_POL_ACTIVE_LOW : 0) |
> -		 ((mode->flags & DRM_MODE_FLAG_NVSYNC) ? SYNCVAL_VS_POL_ACTIVE_LOW : 0));
> -
> -	tc_write(DPIPXLFMT, VS_POL_ACTIVE_LOW | HS_POL_ACTIVE_LOW |
> -		 DE_POL_ACTIVE_HIGH | SUB_CFG_TYPE_CONFIG1 | DPI_BPP_RGB888);
> -
> -	tc_write(DP0_MISC, (max_tu_symbol << 23) | (TU_SIZE_RECOMMENDED << 16) |
> -			   BPC_8);
> +	dev_dbg(tc->dev, "set mode %dx%d\n",
> +		mode->hdisplay, mode->vdisplay);
> +	dev_dbg(tc->dev, "H margin %d,%d sync %d\n",
> +		left_margin, right_margin, hsync_len);
> +	dev_dbg(tc->dev, "V margin %d,%d sync %d\n",
> +		upper_margin, lower_margin, vsync_len);
> +	dev_dbg(tc->dev, "total: %dx%d\n", mode->htotal, mode->vtotal);
>  
> -	return 0;
> -err:
> -	return ret;
> +	return regmap_multi_reg_write(tc->regmap,
> +				      video_mode_settings,
> +				      ARRAY_SIZE(video_mode_settings));
>  }
>  
>  static int tc_wait_link_training(struct tc_data *tc, u32 *error)

I don't like this change. I think multi_reg_write is good for writing
things like, say, color conversion table. But the data for video mode is
more complex and needs more logic (e.g. here ?: operator is used). You
need to stuff all that logic into variable initializers. You can't use
e.g. if() anymore, and you can't even insert a debug print between the
writes if you need to.

So, in my opinion, this doesn't look (much) cleaner, and makes life more
difficult.

 Tomi

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