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From:   Michael Riesch <michael.riesch@wolfvision.net>
Date:   Fri, 04 Aug 2023 15:02:34 +0200
Subject: [PATCH v2 3/4] drm/panel: sitronix-st7789v: add support for
 partial mode
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To:     Rob Herring <robh+dt@kernel.org>,
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        Sebastian Reichel <sre@kernel.org>,
        Gerald Loacker <gerald.loacker@wolfvision.net>
Cc:     devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
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        Michael Riesch <michael.riesch@wolfvision.net>
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The ST7789V controller features support for the partial mode. Here,
the area to be displayed can be restricted in one direction (by default,
in vertical direction). This is useful for panels that are partially
occluded by design. Add support for the partial mode.

Signed-off-by: Michael Riesch <michael.riesch@wolfvision.net>
---
 drivers/gpu/drm/panel/panel-sitronix-st7789v.c | 43 ++++++++++++++++++++++++--
 1 file changed, 41 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/panel/panel-sitronix-st7789v.c b/drivers/gpu/drm/panel/panel-sitronix-st7789v.c
index 0ded72ed2fcd..ebc9a3bd6db3 100644
--- a/drivers/gpu/drm/panel/panel-sitronix-st7789v.c
+++ b/drivers/gpu/drm/panel/panel-sitronix-st7789v.c
@@ -118,6 +118,9 @@ struct st7789_panel_info {
 	u32 bus_format;
 	u32 bus_flags;
 	bool invert_mode;
+	bool partial_mode;
+	u16 partial_start;
+	u16 partial_end;
 };
 
 struct st7789v {
@@ -345,9 +348,14 @@ static enum drm_panel_orientation st7789v_get_orientation(struct drm_panel *p)
 static int st7789v_prepare(struct drm_panel *panel)
 {
 	struct st7789v *ctx = panel_to_st7789v(panel);
-	u8 pixel_fmt, polarity;
+	u8 mode, pixel_fmt, polarity;
 	int ret;
 
+	if (!ctx->info->partial_mode)
+		mode = ST7789V_RGBCTRL_WO;
+	else
+		mode = 0;
+
 	switch (ctx->info->bus_format) {
 	case MEDIA_BUS_FMT_RGB666_1X18:
 		pixel_fmt = MIPI_DCS_PIXEL_FMT_18BIT;
@@ -487,6 +495,37 @@ static int st7789v_prepare(struct drm_panel *panel)
 						MIPI_DCS_EXIT_INVERT_MODE));
 	}
 
+	if (ctx->info->partial_mode) {
+		u8 area_data[4] = {
+			(ctx->info->partial_start >> 8) & 0xff,
+			(ctx->info->partial_start >> 0) & 0xff,
+			((ctx->info->partial_end - 1) >> 8) & 0xff,
+			((ctx->info->partial_end - 1) >> 0) & 0xff,
+		};
+
+		/* Caution: if userspace ever pushes a mode different from the
+		 * expected one (i.e., the one advertised by get_modes), we'll
+		 * add margins.
+		 */
+
+		ST7789V_TEST(ret, st7789v_write_command(
+					  ctx, MIPI_DCS_ENTER_PARTIAL_MODE));
+
+		ST7789V_TEST(ret, st7789v_write_command(
+					  ctx, MIPI_DCS_SET_PAGE_ADDRESS));
+		ST7789V_TEST(ret, st7789v_write_data(ctx, area_data[0]));
+		ST7789V_TEST(ret, st7789v_write_data(ctx, area_data[1]));
+		ST7789V_TEST(ret, st7789v_write_data(ctx, area_data[2]));
+		ST7789V_TEST(ret, st7789v_write_data(ctx, area_data[3]));
+
+		ST7789V_TEST(ret, st7789v_write_command(
+					  ctx, MIPI_DCS_SET_PARTIAL_ROWS));
+		ST7789V_TEST(ret, st7789v_write_data(ctx, area_data[0]));
+		ST7789V_TEST(ret, st7789v_write_data(ctx, area_data[1]));
+		ST7789V_TEST(ret, st7789v_write_data(ctx, area_data[2]));
+		ST7789V_TEST(ret, st7789v_write_data(ctx, area_data[3]));
+	}
+
 	ST7789V_TEST(ret, st7789v_write_command(ctx, ST7789V_RAMCTRL_CMD));
 	ST7789V_TEST(ret, st7789v_write_data(ctx, ST7789V_RAMCTRL_DM_RGB |
 					     ST7789V_RAMCTRL_RM_RGB));
@@ -494,7 +533,7 @@ static int st7789v_prepare(struct drm_panel *panel)
 					     ST7789V_RAMCTRL_MAGIC));
 
 	ST7789V_TEST(ret, st7789v_write_command(ctx, ST7789V_RGBCTRL_CMD));
-	ST7789V_TEST(ret, st7789v_write_data(ctx, ST7789V_RGBCTRL_WO |
+	ST7789V_TEST(ret, st7789v_write_data(ctx, mode |
 					     ST7789V_RGBCTRL_RCM(2) |
 					     polarity));
 	ST7789V_TEST(ret, st7789v_write_data(ctx, ST7789V_RGBCTRL_VBP(8)));

-- 
2.37.2