linux-kernel - [PATCH v2] drm/arm: fixes pixel clock enabled with wrong format

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Message-Id: <20200424063551.14336-1-bernard@vivo.com>
Date:   Thu, 23 Apr 2020 23:35:51 -0700
From:   Bernard Zhao <bernard@...o.com>
To:     Liviu Dudau <liviu.dudau@....com>,
        Brian Starkey <brian.starkey@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Cc:     opensource.kernel@...o.com, Bernard Zhao <bernard@...o.com>
Subject: [PATCH v2] drm/arm: fixes pixel clock enabled with wrong format

The pixel clock is still enabled when the format is wrong.
no error branch handle, and also some register is not set
in this case, e.g: HDLCD_REG_<color>_SELECT. Maybe we
should disable this clock and throw an warn message when
this happened.
With this change, the code maybe a bit more readable.

Signed-off-by: Bernard Zhao <bernard@...o.com>

Changes since V1:
*add format error handle, if format is not correct, throw
an warning message and disable this clock.

Link for V1:
*https://lore.kernel.org/patchwork/patch/1228501/
---
 drivers/gpu/drm/arm/hdlcd_crtc.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/arm/hdlcd_crtc.c b/drivers/gpu/drm/arm/hdlcd_crtc.c
index af67fefed38d..f3945dee2b7d 100644
--- a/drivers/gpu/drm/arm/hdlcd_crtc.c
+++ b/drivers/gpu/drm/arm/hdlcd_crtc.c
@@ -96,7 +96,7 @@ static int hdlcd_set_pxl_fmt(struct drm_crtc *crtc)
 	}
 
 	if (WARN_ON(!format))
-		return 0;
+		return -EINVAL;
 
 	/* HDLCD uses 'bytes per pixel', zero means 1 byte */
 	btpp = (format->bits_per_pixel + 7) / 8;
@@ -125,7 +125,7 @@ static int hdlcd_set_pxl_fmt(struct drm_crtc *crtc)
 	return 0;
 }
 
-static void hdlcd_crtc_mode_set_nofb(struct drm_crtc *crtc)
+static int hdlcd_crtc_mode_set_nofb(struct drm_crtc *crtc)
 {
 	struct hdlcd_drm_private *hdlcd = crtc_to_hdlcd_priv(crtc);
 	struct drm_display_mode *m = &crtc->state->adjusted_mode;
@@ -162,9 +162,10 @@ static void hdlcd_crtc_mode_set_nofb(struct drm_crtc *crtc)
 
 	err = hdlcd_set_pxl_fmt(crtc);
 	if (err)
-		return;
+		return err;
 
 	clk_set_rate(hdlcd->clk, m->crtc_clock * 1000);
+	return 0;
 }
 
 static void hdlcd_crtc_atomic_enable(struct drm_crtc *crtc,
@@ -173,7 +174,11 @@ static void hdlcd_crtc_atomic_enable(struct drm_crtc *crtc,
 	struct hdlcd_drm_private *hdlcd = crtc_to_hdlcd_priv(crtc);
 
 	clk_prepare_enable(hdlcd->clk);
-	hdlcd_crtc_mode_set_nofb(crtc);
+	if (hdlcd_crtc_mode_set_nofb(crtc)) {
+		DRM_DEBUG_KMS("Invalid format, pixel clock enable failed!\n");
+		clk_disable_unprepare(hdlcd->clk);
+		return;
+	}
 	hdlcd_write(hdlcd, HDLCD_REG_COMMAND, 1);
 	drm_crtc_vblank_on(crtc);
 }
-- 
2.26.2