linux-kernel - [PATCH 06/15] drm/vc4: hdmi: Compute the CEC clock divider from the clock rate

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Message-Id: <20201210134648.272857-7-maxime@cerno.tech>
Date:   Thu, 10 Dec 2020 14:46:39 +0100
From:   Maxime Ripard <maxime@...no.tech>
To:     Eric Anholt <eric@...olt.net>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Maxime Ripard <maxime@...no.tech>,
        Daniel Vetter <daniel.vetter@...el.com>,
        David Airlie <airlied@...ux.ie>
Cc:     Jason Cooper <jason@...edaemon.net>,
        bcm-kernel-feedback-list@...adcom.com,
        linux-arm-kernel@...ts.infradead.org,
        Marc Zyngier <maz@...nel.org>, linux-media@...r.kernel.org,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        linux-kernel@...r.kernel.org,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        linux-rpi-kernel@...ts.infradead.org,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH 06/15] drm/vc4: hdmi: Compute the CEC clock divider from the clock rate

The CEC clock divider needs to output a frequency of 40kHz from the HSM
rate on the BCM2835. The driver used to have a fixed frequency for it,
but that changed and we now need to compute it dynamically to maintain
the proper rate.

Fixes: cd4cb49dc5bb ("drm/vc4: hdmi: Adjust HSM clock rate depending on pixel rate")
Signed-off-by: Maxime Ripard <maxime@...no.tech>
---
 drivers/gpu/drm/vc4/vc4_hdmi.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index eff3bac562c6..0c53d7427d15 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -1586,6 +1586,7 @@ static int vc4_hdmi_cec_init(struct vc4_hdmi *vc4_hdmi)
 {
 	struct cec_connector_info conn_info;
 	struct platform_device *pdev = vc4_hdmi->pdev;
+	u16 clk_cnt;
 	u32 value;
 	int ret;
 
@@ -1611,8 +1612,9 @@ static int vc4_hdmi_cec_init(struct vc4_hdmi *vc4_hdmi)
 	 * divider: the hsm_clock rate and this divider setting will
 	 * give a 40 kHz CEC clock.
 	 */
+	clk_cnt = clk_get_rate(vc4_hdmi->hsm_clock) / CEC_CLOCK_FREQ;
 	value |= VC4_HDMI_CEC_ADDR_MASK |
-		 (4091 << VC4_HDMI_CEC_DIV_CLK_CNT_SHIFT);
+		 (clk_cnt << VC4_HDMI_CEC_DIV_CLK_CNT_SHIFT);
 	HDMI_WRITE(HDMI_CEC_CNTRL_1, value);
 	ret = devm_request_threaded_irq(&pdev->dev, platform_get_irq(pdev, 0),
 					vc4_cec_irq_handler,
-- 
2.28.0