[PATCH v2 1/2] drm: bridge: samsung-dsim: Initialize bridge on attach

[Marek Vasut]

Initialize the bridge on attach already, to force lanes into LP11
state, since attach does trigger attach of downstream bridges which
may trigger (e)DP AUX channel mode read.

This fixes a corner case where DSIM with TC9595 attached to it fails
to operate the DP AUX channel, because the TC9595 enters some debug
mode when it is released from reset without lanes in LP11 mode. By
ensuring the DSIM lanes are in LP11, the TC9595 (tc358767.c driver)
can be reset in its attach callback called from DSIM attach callback,
and recovered out of the debug mode just before TC9595 performs first
AUX channel access later in its attach callback.

Signed-off-by: Marek Vasut <marex at denx.de>
---
Cc: Adam Ford <aford173 at gmail.com>
Cc: Alexander Stein <alexander.stein at ew.tq-group.com>
Cc: Andrzej Hajda <andrzej.hajda at intel.com>
Cc: Daniel Vetter <daniel at ffwll.ch>
Cc: David Airlie <airlied at gmail.com>
Cc: Frieder Schrempf <frieder.schrempf at kontron.de>
Cc: Inki Dae <inki.dae at samsung.com>
Cc: Jagan Teki <jagan at amarulasolutions.com>
Cc: Jernej Skrabec <jernej.skrabec at gmail.com>
Cc: Jonas Karlman <jonas at kwiboo.se>
Cc: Laurent Pinchart <Laurent.pinchart at ideasonboard.com>
Cc: Lucas Stach <l.stach at pengutronix.de>
Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Cc: Marek Szyprowski <m.szyprowski at samsung.com>
Cc: Maxime Ripard <mripard at kernel.org>
Cc: Michael Walle <mwalle at kernel.org>
Cc: Neil Armstrong <neil.armstrong at linaro.org>
Cc: Robert Foss <rfoss at kernel.org>
Cc: Thomas Zimmermann <tzimmermann at suse.de>
Cc: dri-devel at lists.freedesktop.org
Cc: kernel at dh-electronics.com
---
V2: Handle case where mode is not set yet
---
 drivers/gpu/drm/bridge/samsung-dsim.c | 32 ++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
index e7e53a9e42afb..22d3bbd866d97 100644
--- a/drivers/gpu/drm/bridge/samsung-dsim.c
+++ b/drivers/gpu/drm/bridge/samsung-dsim.c
@@ -699,20 +699,24 @@ static unsigned long samsung_dsim_set_pll(struct samsung_dsim *dsi,
 
 static int samsung_dsim_enable_clock(struct samsung_dsim *dsi)
 {
-	unsigned long hs_clk, byte_clk, esc_clk, pix_clk;
+	unsigned long hs_clk, byte_clk, esc_clk;
 	unsigned long esc_div;
 	u32 reg;
 	struct drm_display_mode *m = &dsi->mode;
 	int bpp = mipi_dsi_pixel_format_to_bpp(dsi->format);
 
-	/* m->clock is in KHz */
-	pix_clk = m->clock * 1000;
-
-	/* Use burst_clk_rate if available, otherwise use the pix_clk */
+	/*
+	 * Use burst_clk_rate if available, otherwise use the mode clock
+	 * if mode is already set and available, otherwise fall back to
+	 * PLL input clock and operate in 1:1 lowest frequency mode until
+	 * a mode is set.
+	 */
 	if (dsi->burst_clk_rate)
 		hs_clk = samsung_dsim_set_pll(dsi, dsi->burst_clk_rate);
+	else if (m)	/* m->clock is in KHz */
+		hs_clk = samsung_dsim_set_pll(dsi, DIV_ROUND_UP(m->clock * 1000 * bpp, dsi->lanes));
 	else
-		hs_clk = samsung_dsim_set_pll(dsi, DIV_ROUND_UP(pix_clk * bpp, dsi->lanes));
+		hs_clk = dsi->pll_clk_rate;
 
 	if (!hs_clk) {
 		dev_err(dsi->dev, "failed to configure DSI PLL\n");
@@ -1643,9 +1647,21 @@ static int samsung_dsim_attach(struct drm_bridge *bridge,
 			       enum drm_bridge_attach_flags flags)
 {
 	struct samsung_dsim *dsi = bridge_to_dsi(bridge);
+	int ret;
 
-	return drm_bridge_attach(bridge->encoder, dsi->out_bridge, bridge,
-				 flags);
+	ret = pm_runtime_resume_and_get(dsi->dev);
+	if (ret < 0)
+		return ret;
+
+	ret = samsung_dsim_init(dsi);
+	if (ret < 0)
+		goto err;
+
+	ret = drm_bridge_attach(bridge->encoder, dsi->out_bridge, bridge,
+				flags);
+err:
+	pm_runtime_put_sync(dsi->dev);
+	return ret;
 }
 
 static const struct drm_bridge_funcs samsung_dsim_bridge_funcs = {
-- 
2.43.0