drm/tegra: dc: rgb: Allow changing PLLD rate on Tegra30+

Asus Transformer TF700T is a Tegra30 tablet device which uses RGB->DSI
bridge that requires a precise clock rate in order to operate properly.
Tegra30 has a dedicated PLL for each display controller, hence the PLL
rate can be changed freely. Allow PLL rate changes on Tegra30+ for RGB
output. Configure the clock rate before display controller is enabled
since DC itself may be running off this PLL and it's not okay to change
the rate of the active PLL that doesn't support dynamic frequency
switching since hardware will hang.

Tested-by: Maxim Schwalm <maxim.schwalm@gmail.com> #TF700T
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

1 files changed, 47 insertions, 2 deletions

diff --git a/drivers/gpu/drm/tegra/rgb.c b/drivers/gpu/drm/tegra/rgb.c
index 933e14e4609f..ff8fce36d2aa 100644
--- a/drivers/gpu/drm/tegra/rgb.c
+++ b/drivers/gpu/drm/tegra/rgb.c
@@ -17,6 +17,8 @@ struct tegra_rgb {
 	struct tegra_output output;
 	struct tegra_dc *dc;
 
+	struct clk *pll_d_out0;
+	struct clk *pll_d2_out0;
 	struct clk *clk_parent;
 	struct clk *clk;
 };
@@ -119,6 +121,18 @@ static void tegra_rgb_encoder_enable(struct drm_encoder *encoder)
 	tegra_dc_commit(rgb->dc);
 }
 
+static bool tegra_rgb_pll_rate_change_allowed(struct tegra_rgb *rgb)
+{
+	if (!rgb->pll_d2_out0)
+		return false;
+
+	if (!clk_is_match(rgb->clk_parent, rgb->pll_d_out0) &&
+	    !clk_is_match(rgb->clk_parent, rgb->pll_d2_out0))
+		return false;
+
+	return true;
+}
+
 static int
 tegra_rgb_encoder_atomic_check(struct drm_encoder *encoder,
 			       struct drm_crtc_state *crtc_state,
@@ -147,8 +161,17 @@ tegra_rgb_encoder_atomic_check(struct drm_encoder *encoder,
 	 * and hope that the desired frequency can be matched (or at least
 	 * matched sufficiently close that the panel will still work).
 	 */
-	div = ((clk_get_rate(rgb->clk) * 2) / pclk) - 2;
-	pclk = 0;
+	if (tegra_rgb_pll_rate_change_allowed(rgb)) {
+		/*
+		 * Set display controller clock to x2 of PCLK in order to
+		 * produce higher resolution pulse positions.
+		 */
+		div = 2;
+		pclk *= 2;
+	} else {
+		div = ((clk_get_rate(rgb->clk) * 2) / pclk) - 2;
+		pclk = 0;
+	}
 
 	err = tegra_dc_state_setup_clock(dc, crtc_state, rgb->clk_parent,
 					 pclk, div);
@@ -206,6 +229,22 @@ int tegra_dc_rgb_probe(struct tegra_dc *dc)
 		return err;
 	}
 
+	rgb->pll_d_out0 = clk_get_sys(NULL, "pll_d_out0");
+	if (IS_ERR(rgb->pll_d_out0)) {
+		err = PTR_ERR(rgb->pll_d_out0);
+		dev_err(dc->dev, "failed to get pll_d_out0: %d\n", err);
+		return err;
+	}
+
+	if (dc->soc->has_pll_d2_out0) {
+		rgb->pll_d2_out0 = clk_get_sys(NULL, "pll_d2_out0");
+		if (IS_ERR(rgb->pll_d2_out0)) {
+			err = PTR_ERR(rgb->pll_d2_out0);
+			dev_err(dc->dev, "failed to get pll_d2_out0: %d\n", err);
+			return err;
+		}
+	}
+
 	dc->rgb = &rgb->output;
 
 	return 0;
@@ -213,9 +252,15 @@ int tegra_dc_rgb_probe(struct tegra_dc *dc)
 
 int tegra_dc_rgb_remove(struct tegra_dc *dc)
 {
+	struct tegra_rgb *rgb;
+
 	if (!dc->rgb)
 		return 0;
 
+	rgb = to_rgb(dc->rgb);
+	clk_put(rgb->pll_d2_out0);
+	clk_put(rgb->pll_d_out0);
+
 	tegra_output_remove(dc->rgb);
 	dc->rgb = NULL;