linux-kernel - Re: [PATCH 07/15] drm/vc4: hdmi: Update the CEC clock divider on HSM rate change

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Date:   Fri, 18 Dec 2020 14:26:57 +0000
From:   Dave Stevenson <dave.stevenson@...pberrypi.com>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     Eric Anholt <eric@...olt.net>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Daniel Vetter <daniel.vetter@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Jason Cooper <jason@...edaemon.net>,
        bcm-kernel-feedback-list@...adcom.com,
        linux-arm-kernel@...ts.infradead.org,
        Marc Zyngier <maz@...nel.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        LKML <linux-kernel@...r.kernel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-rpi-kernel@...ts.infradead.org,
        DRI Development <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH 07/15] drm/vc4: hdmi: Update the CEC clock divider on HSM
 rate change

Hi Maxime

On Thu, 10 Dec 2020 at 13:47, Maxime Ripard <maxime@...no.tech> wrote:
>
> As part of the enable sequence we might change the HSM clock rate if the
> pixel rate is different than the one we were already dealing with.
>
> On the BCM2835 however, the CEC clock derives from the HSM clock so any
> rate change will need to be reflected in the CEC clock divider to output
> 40kHz.
>
> Fixes: cd4cb49dc5bb ("drm/vc4: hdmi: Adjust HSM clock rate depending on pixel rate")
> Signed-off-by: Maxime Ripard <maxime@...no.tech>

I thought we'd got a duplicate patch here, but it's moving code that
was changed in patch 6/15 so it can be called from
vc4_hdmi_encoder_pre_crtc_configure too. Good for confusing me!

Reviewed-by: Dave Stevenson <dave.stevenson@...pberrypi.com>

> ---
>  drivers/gpu/drm/vc4/vc4_hdmi.c | 39 +++++++++++++++++++++++++---------
>  1 file changed, 29 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
> index 0c53d7427d15..b93ee3e26e2b 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> @@ -132,6 +132,27 @@ static void vc5_hdmi_reset(struct vc4_hdmi *vc4_hdmi)
>                    HDMI_READ(HDMI_CLOCK_STOP) | VC4_DVP_HT_CLOCK_STOP_PIXEL);
>  }
>
> +#ifdef CONFIG_DRM_VC4_HDMI_CEC
> +static void vc4_hdmi_cec_update_clk_div(struct vc4_hdmi *vc4_hdmi)
> +{
> +       u16 clk_cnt;
> +       u32 value;
> +
> +       value = HDMI_READ(HDMI_CEC_CNTRL_1);
> +       value &= ~VC4_HDMI_CEC_DIV_CLK_CNT_MASK;
> +
> +       /*
> +        * Set the clock 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 |= clk_cnt << VC4_HDMI_CEC_DIV_CLK_CNT_SHIFT;
> +       HDMI_WRITE(HDMI_CEC_CNTRL_1, value);
> +}
> +#else
> +static void vc4_hdmi_cec_update_clk_div(struct vc4_hdmi *vc4_hdmi) {}
> +#endif
> +
>  static enum drm_connector_status
>  vc4_hdmi_connector_detect(struct drm_connector *connector, bool force)
>  {
> @@ -761,6 +782,8 @@ static void vc4_hdmi_encoder_pre_crtc_configure(struct drm_encoder *encoder,
>                 return;
>         }
>
> +       vc4_hdmi_cec_update_clk_div(vc4_hdmi);
> +
>         /*
>          * FIXME: When the pixel freq is 594MHz (4k60), this needs to be setup
>          * at 300MHz.
> @@ -1586,7 +1609,6 @@ 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;
>
> @@ -1605,17 +1627,14 @@ static int vc4_hdmi_cec_init(struct vc4_hdmi *vc4_hdmi)
>         cec_s_conn_info(vc4_hdmi->cec_adap, &conn_info);
>
>         HDMI_WRITE(HDMI_CEC_CPU_MASK_SET, 0xffffffff);
> +
>         value = HDMI_READ(HDMI_CEC_CNTRL_1);
> -       value &= ~VC4_HDMI_CEC_DIV_CLK_CNT_MASK;
> -       /*
> -        * Set the logical address to Unregistered and set the clock
> -        * 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 |
> -                (clk_cnt << VC4_HDMI_CEC_DIV_CLK_CNT_SHIFT);
> +       /* Set the logical address to Unregistered */
> +       value |= VC4_HDMI_CEC_ADDR_MASK;
>         HDMI_WRITE(HDMI_CEC_CNTRL_1, value);
> +
> +       vc4_hdmi_cec_update_clk_div(vc4_hdmi);
> +
>         ret = devm_request_threaded_irq(&pdev->dev, platform_get_irq(pdev, 0),
>                                         vc4_cec_irq_handler,
>                                         vc4_cec_irq_handler_thread, 0,
> --
> 2.28.0
>