[RFC PATCH 05/16] drm/rockchip: ebc: Add CRTC mode setting

[Samuel Holland]

EPDs require some additional timing data beyond what is normally
provided by drm_display_mode, as that struct is designed for CRTs/LCDs.
For example, EPDs care about the width and position of the gate driver
(vertical) clock pulse within a line.

EPDs also update some number of pixels in parallel, based on the
interface width, which of course varies by panel. Only two data bits are
used for each pixel, to choose between driving it positive, negative, or
neither direction. Color depth is thus not limited by interface width,
but by time (the number of phases in the active waveform).

This additional timing information is packed inside drm_display_mode as
hskew and DRM_MODE_FLAG_CLKDIV2. This allows getting the complete mode
from a DRM bridge.

Signed-off-by: Samuel Holland <samuel at sholland.org>
---

 drivers/gpu/drm/rockchip/rockchip_ebc.c | 102 ++++++++++++++++++++++++
 1 file changed, 102 insertions(+)

diff --git a/drivers/gpu/drm/rockchip/rockchip_ebc.c b/drivers/gpu/drm/rockchip/rockchip_ebc.c
index f75fd23adda2..5f9502313657 100644
--- a/drivers/gpu/drm/rockchip/rockchip_ebc.c
+++ b/drivers/gpu/drm/rockchip/rockchip_ebc.c
@@ -135,6 +135,7 @@ struct rockchip_ebc {
 	struct drm_plane		plane;
 	struct regmap			*regmap;
 	struct regulator_bulk_data	supplies[EBC_NUM_SUPPLIES];
+	u32				dsp_start;
 };
 
 DEFINE_DRM_GEM_FOPS(rockchip_ebc_fops);
@@ -178,11 +179,112 @@ static inline struct rockchip_ebc *crtc_to_ebc(struct drm_crtc *crtc)
 
 static void rockchip_ebc_crtc_mode_set_nofb(struct drm_crtc *crtc)
 {
+	struct rockchip_ebc *ebc = crtc_to_ebc(crtc);
+	struct drm_display_mode mode = crtc->state->adjusted_mode;
+	struct drm_display_mode sdck;
+	u16 hsync_width, vsync_width;
+	u16 hact_start, vact_start;
+	u16 pixels_per_sdck;
+	bool bus_16bit;
+
+	/*
+	 * Hardware needs horizontal timings in SDCK (source driver clock)
+	 * cycles, not pixels. Bus width is either 8 bits (normal) or 16 bits
+	 * (DRM_MODE_FLAG_CLKDIV2), and each pixel uses two data bits.
+	 */
+	bus_16bit = !!(mode.flags & DRM_MODE_FLAG_CLKDIV2);
+	pixels_per_sdck = bus_16bit ? 8 : 4;
+	sdck.hdisplay = mode.hdisplay / pixels_per_sdck;
+	sdck.hsync_start = mode.hsync_start / pixels_per_sdck;
+	sdck.hsync_end = mode.hsync_end / pixels_per_sdck;
+	sdck.htotal = mode.htotal / pixels_per_sdck;
+	sdck.hskew = mode.hskew / pixels_per_sdck;
+
+	/*
+	 * Linux timing order is display/fp/sync/bp. Hardware timing order is
+	 * sync/bp/display/fp, aka sync/start/display/end.
+	 */
+	hact_start = sdck.htotal - sdck.hsync_start;
+	vact_start = mode.vtotal - mode.vsync_start;
+
+	hsync_width = sdck.hsync_end - sdck.hsync_start;
+	vsync_width = mode.vsync_end - mode.vsync_start;
+
+	clk_set_rate(ebc->dclk, mode.clock * 1000);
+
+	ebc->dsp_start = EBC_DSP_START_DSP_SDCE_WIDTH(sdck.hdisplay) |
+			 EBC_DSP_START_SW_BURST_CTRL;
+	regmap_write(ebc->regmap, EBC_EPD_CTRL,
+		     EBC_EPD_CTRL_DSP_GD_END(sdck.htotal - sdck.hskew) |
+		     EBC_EPD_CTRL_DSP_GD_ST(hsync_width + sdck.hskew) |
+		     EBC_EPD_CTRL_DSP_SDDW_MODE * bus_16bit);
+	regmap_write(ebc->regmap, EBC_DSP_CTRL,
+		     /* no swap */
+		     EBC_DSP_CTRL_DSP_SWAP_MODE(bus_16bit ? 2 : 3) |
+		     EBC_DSP_CTRL_DSP_SDCLK_DIV(pixels_per_sdck - 1));
+	regmap_write(ebc->regmap, EBC_DSP_HTIMING0,
+		     EBC_DSP_HTIMING0_DSP_HTOTAL(sdck.htotal) |
+		     /* sync end == sync width */
+		     EBC_DSP_HTIMING0_DSP_HS_END(hsync_width));
+	regmap_write(ebc->regmap, EBC_DSP_HTIMING1,
+		     EBC_DSP_HTIMING1_DSP_HACT_END(hact_start + sdck.hdisplay) |
+		     /* minus 1 for fixed delay in timing sequence */
+		     EBC_DSP_HTIMING1_DSP_HACT_ST(hact_start - 1));
+	regmap_write(ebc->regmap, EBC_DSP_VTIMING0,
+		     EBC_DSP_VTIMING0_DSP_VTOTAL(mode.vtotal) |
+		     /* sync end == sync width */
+		     EBC_DSP_VTIMING0_DSP_VS_END(vsync_width));
+	regmap_write(ebc->regmap, EBC_DSP_VTIMING1,
+		     EBC_DSP_VTIMING1_DSP_VACT_END(vact_start + mode.vdisplay) |
+		     EBC_DSP_VTIMING1_DSP_VACT_ST(vact_start));
+	regmap_write(ebc->regmap, EBC_DSP_ACT_INFO,
+		     EBC_DSP_ACT_INFO_DSP_HEIGHT(mode.vdisplay) |
+		     EBC_DSP_ACT_INFO_DSP_WIDTH(mode.hdisplay));
+	regmap_write(ebc->regmap, EBC_WIN_CTRL,
+		     /* FIFO depth - 16 */
+		     EBC_WIN_CTRL_WIN2_FIFO_THRESHOLD(496) |
+		     EBC_WIN_CTRL_WIN_EN |
+		     /* INCR16 */
+		     EBC_WIN_CTRL_AHB_BURST_REG(7) |
+		     /* FIFO depth - 16 */
+		     EBC_WIN_CTRL_WIN_FIFO_THRESHOLD(240) |
+		     EBC_WIN_CTRL_WIN_FMT_Y4);
+
+	/* To keep things simple, always use a window size matching the CRTC. */
+	regmap_write(ebc->regmap, EBC_WIN_VIR,
+		     EBC_WIN_VIR_WIN_VIR_HEIGHT(mode.vdisplay) |
+		     EBC_WIN_VIR_WIN_VIR_WIDTH(mode.hdisplay));
+	regmap_write(ebc->regmap, EBC_WIN_ACT,
+		     EBC_WIN_ACT_WIN_ACT_HEIGHT(mode.vdisplay) |
+		     EBC_WIN_ACT_WIN_ACT_WIDTH(mode.hdisplay));
+	regmap_write(ebc->regmap, EBC_WIN_DSP,
+		     EBC_WIN_DSP_WIN_DSP_HEIGHT(mode.vdisplay) |
+		     EBC_WIN_DSP_WIN_DSP_WIDTH(mode.hdisplay));
+	regmap_write(ebc->regmap, EBC_WIN_DSP_ST,
+		     EBC_WIN_DSP_ST_WIN_DSP_YST(vact_start) |
+		     EBC_WIN_DSP_ST_WIN_DSP_XST(hact_start));
 }
 
 static int rockchip_ebc_crtc_atomic_check(struct drm_crtc *crtc,
 					  struct drm_atomic_state *state)
 {
+	struct rockchip_ebc *ebc = crtc_to_ebc(crtc);
+	struct drm_crtc_state *crtc_state;
+
+	crtc_state = drm_atomic_get_new_crtc_state(state, crtc);
+	if (!crtc_state->mode_changed)
+		return 0;
+
+	if (crtc_state->enable) {
+		struct drm_display_mode *mode = &crtc_state->adjusted_mode;
+		long rate = mode->clock * 1000;
+
+		rate = clk_round_rate(ebc->dclk, rate);
+		if (rate < 0)
+			return rate;
+		mode->clock = rate / 1000;
+	}
+
 	return 0;
 }
 
-- 
2.35.1