linux-kernel - [PATCH v3 2/3] drm/tilcdc: fix LCD pixel clock setting

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Date:   Mon, 22 Mar 2021 22:33:36 +0100
From:   Dario Binacchi <dariobin@...ero.it>
To:     linux-kernel@...r.kernel.org
Cc:     Dario Binacchi <dariobin@...ero.it>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Jyri Sarha <jyri.sarha@....fi>,
        Tomi Valkeinen <tomba@...nel.org>,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH v3 2/3] drm/tilcdc: fix LCD pixel clock setting

The tilcdc_pclk_diff() compares the requested pixel clock rate to the
real one, so passing it clk_rate instead of clk_rate / clkdiv caused
it to fail even if the clk_rate was properly set. Adding the
real_pclk_rate variable makes the code more readable.

Signed-off-by: Dario Binacchi <dariobin@...ero.it>

---

(no changes since v2)

Changes in v2:
- Rename clk_div_rate to real_pclk_rate.
- Provide pixel clock rate to tilcdc_pclk_diff().

 drivers/gpu/drm/tilcdc/tilcdc_crtc.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
index aeec5786617d..ac6228cb04d9 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
+++ b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
@@ -203,7 +203,7 @@ static void tilcdc_crtc_set_clk(struct drm_crtc *crtc)
 	struct drm_device *dev = crtc->dev;
 	struct tilcdc_drm_private *priv = dev->dev_private;
 	struct tilcdc_crtc *tilcdc_crtc = to_tilcdc_crtc(crtc);
-	unsigned long clk_rate, real_rate, pclk_rate;
+	unsigned long clk_rate, real_rate, real_pclk_rate, pclk_rate;
 	unsigned int clkdiv;
 	int ret;
 
@@ -214,7 +214,8 @@ static void tilcdc_crtc_set_clk(struct drm_crtc *crtc)
 
 	ret = clk_set_rate(priv->clk, pclk_rate * clkdiv);
 	clk_rate = clk_get_rate(priv->clk);
-	if (ret < 0 || tilcdc_pclk_diff(pclk_rate, clk_rate) > 5) {
+	real_pclk_rate = clk_rate / clkdiv;
+	if (ret < 0 || tilcdc_pclk_diff(pclk_rate, real_pclk_rate) > 5) {
 		/*
 		 * If we fail to set the clock rate (some architectures don't
 		 * use the common clock framework yet and may not implement
-- 
2.17.1