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 for the BCM2711 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")
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Tested-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Link: https://patchwork.freedesktop.org/patch/msgid/20210111142309.193441-7-maxime@cerno.tech
(cherry picked from commit f1ceb9d10043683b89e5e5e5848fb4e855295762)
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index df2c05f..cf4b5f5 100644 (file)
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -1599,6 +1599,7 @@ 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;
 
@@ -1624,8 +1625,9 @@ 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,