[PATCH v3] drm/bridge/synopsys: dsi: add optional pixel clock

[Philippe Cornu <philippe.cornu@st.com>]

The pixel clock is optional. When available, it offers a better
preciseness for timing computations and allows to reduce the extra dsi
bandwidth in burst mode (from ~20% to ~10-12%, hw platform dependant).

Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Philippe Cornu <philippe.cornu@st.com>
---
Changes in v3: Simplify px_clk probing thanks to Andrzej Hajda comments

Changes in v2: Improve px_clk probing in case of ENOENT dt returned value
(thanks to Philipp Zabel & Andrzej Hajda comments)

 drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
index ed8af32f8e52..9fb35385c348 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
@@ -217,6 +217,7 @@ struct dw_mipi_dsi {
 	void __iomem *base;
 
 	struct clk *pclk;
+	struct clk *px_clk;
 
 	unsigned int lane_mbps; /* per lane */
 	u32 channel;
@@ -703,24 +704,28 @@ static void dw_mipi_dsi_bridge_mode_set(struct drm_bridge *bridge,
 	struct dw_mipi_dsi *dsi = bridge_to_dsi(bridge);
 	const struct dw_mipi_dsi_phy_ops *phy_ops = dsi->plat_data->phy_ops;
 	void *priv_data = dsi->plat_data->priv_data;
+	struct drm_display_mode px_clk_mode = *mode;
 	int ret;
 
 	clk_prepare_enable(dsi->pclk);
 
-	ret = phy_ops->get_lane_mbps(priv_data, mode, dsi->mode_flags,
+	if (dsi->px_clk)
+		px_clk_mode.clock = clk_get_rate(dsi->px_clk) / 1000;
+
+	ret = phy_ops->get_lane_mbps(priv_data, &px_clk_mode, dsi->mode_flags,
 				     dsi->lanes, dsi->format, &dsi->lane_mbps);
 	if (ret)
 		DRM_DEBUG_DRIVER("Phy get_lane_mbps() failed\n");
 
 	pm_runtime_get_sync(dsi->dev);
 	dw_mipi_dsi_init(dsi);
-	dw_mipi_dsi_dpi_config(dsi, mode);
+	dw_mipi_dsi_dpi_config(dsi, &px_clk_mode);
 	dw_mipi_dsi_packet_handler_config(dsi);
 	dw_mipi_dsi_video_mode_config(dsi);
-	dw_mipi_dsi_video_packet_config(dsi, mode);
+	dw_mipi_dsi_video_packet_config(dsi, &px_clk_mode);
 	dw_mipi_dsi_command_mode_config(dsi);
-	dw_mipi_dsi_line_timer_config(dsi, mode);
-	dw_mipi_dsi_vertical_timing_config(dsi, mode);
+	dw_mipi_dsi_line_timer_config(dsi, &px_clk_mode);
+	dw_mipi_dsi_vertical_timing_config(dsi, &px_clk_mode);
 
 	dw_mipi_dsi_dphy_init(dsi);
 	dw_mipi_dsi_dphy_timing_config(dsi);
@@ -734,7 +739,7 @@ static void dw_mipi_dsi_bridge_mode_set(struct drm_bridge *bridge,
 
 	dw_mipi_dsi_dphy_enable(dsi);
 
-	dw_mipi_dsi_wait_for_two_frames(mode);
+	dw_mipi_dsi_wait_for_two_frames(&px_clk_mode);
 
 	/* Switch to cmd mode for panel-bridge pre_enable & panel prepare */
 	dw_mipi_dsi_set_mode(dsi, 0);
@@ -828,6 +833,14 @@ __dw_mipi_dsi_probe(struct platform_device *pdev,
 		return ERR_PTR(ret);
 	}
 
+	dsi->px_clk = devm_clk_get(dev, "px_clk");
+	if (IS_ERR(dsi->px_clk)) {
+		ret = PTR_ERR(dsi->px_clk);
+		if (ret != ENOENT)
+			dev_err(dev, "Unable to get opt. px_clk: %d\n", ret);
+		dsi->px_clk = NULL;
+	}
+
 	/*
 	 * Note that the reset was not defined in the initial device tree, so
 	 * we have to be prepared for it not being found.
-- 
2.15.1