linux-kernel - Re: [v2,03/10] drm/sun4i: Protect the TCON pixel clocks

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Message-ID: <287984f8-bcac-3789-d573-2f0c54fb537d@micronovasrl.com>
Date:   Fri, 23 Feb 2018 15:05:26 +0100
From:   Giulio Benetti <giulio.benetti@...ronovasrl.com>
To:     Maxime Ripard <maxime.ripard@...tlin.com>,
        Mark Brown <broonie@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [v2,03/10] drm/sun4i: Protect the TCON pixel clocks

From: Maxime Ripard <maxime.ripard@...e-electrons.com>

Both TCON clocks are very sensitive to clock changes, since any change
might lead to improper timings.

Make sure our rate is never changed.

Tested-by: Giulio Benetti <giulio.benetti@...ronovasrl.com>
Signed-off-by: Maxime Ripard <maxime.ripard@...e-electrons.com>
---
  drivers/gpu/drm/sun4i/sun4i_tcon.c | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c 
b/drivers/gpu/drm/sun4i/sun4i_tcon.c
index b73acab74867..cbe87cee13d1 100644
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
@@ -261,7 +261,7 @@ static void sun4i_tcon0_mode_set_common(struct 
sun4i_tcon *tcon,
  					const struct drm_display_mode *mode)
  {
  	/* Configure the dot clock */
-	clk_set_rate(tcon->dclk, mode->crtc_clock * 1000);
+	clk_set_rate_exclusive(tcon->dclk, mode->crtc_clock * 1000);

  	/* Set the resolution */
  	regmap_write(tcon->regs, SUN4I_TCON0_BASIC0_REG,
@@ -419,7 +419,7 @@ static void sun4i_tcon1_mode_set(struct sun4i_tcon 
*tcon,
  	WARN_ON(!tcon->quirks->has_channel_1);

  	/* Configure the dot clock */
-	clk_set_rate(tcon->sclk1, mode->crtc_clock * 1000);
+	clk_set_rate_exclusive(tcon->sclk1, mode->crtc_clock * 1000);

  	/* Adjust clock delay */
  	clk_delay = sun4i_tcon_get_clk_delay(mode, 1);