linux-kernel - Re: [PATCH 4/4] drm/meson: dw-hdmi: Ensure that clocks are enabled before touching the TOP registers

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Date:   Tue, 17 Nov 2020 09:56:43 +0100
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Marc Zyngier <maz@...nel.org>, Kevin Hilman <khilman@...libre.com>
Cc:     Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        kernel-team@...roid.com, dri-devel@...ts.freedesktop.org,
        linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] drm/meson: dw-hdmi: Ensure that clocks are enabled
 before touching the TOP registers

On 16/11/2020 21:07, Marc Zyngier wrote:
> Removing the meson-dw-hdmi module and re-inserting it results in a hang
> as the driver writes to HDMITX_TOP_SW_RESET. Similar effects can be seen
> when booting with mainline u-boot and using the u-boot provided DT (which
> is highly desirable).
> 
> The reason for the hang seem to be that the clocks are not always
> enabled by the time we enter meson_dw_hdmi_init(). Moving this call
> *after* dw_hdmi_probe() ensures that the clocks are enabled.
> 
> Signed-off-by: Marc Zyngier <maz@...nel.org>

Fixes: 1374b8375c2e ("drm/meson: dw_hdmi: add resume/suspend hooks")

> ---
>  drivers/gpu/drm/meson/meson_dw_hdmi.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/meson/meson_dw_hdmi.c b/drivers/gpu/drm/meson/meson_dw_hdmi.c
> index 68826cf9993f..7f8eea494147 100644
> --- a/drivers/gpu/drm/meson/meson_dw_hdmi.c
> +++ b/drivers/gpu/drm/meson/meson_dw_hdmi.c
> @@ -1073,8 +1073,6 @@ static int meson_dw_hdmi_bind(struct device *dev, struct device *master,
>  
>  	DRM_DEBUG_DRIVER("encoder initialized\n");
>  
> -	meson_dw_hdmi_init(meson_dw_hdmi);
> -
>  	/* Bridge / Connector */
>  
>  	dw_plat_data->priv_data = meson_dw_hdmi;
> @@ -1097,6 +1095,8 @@ static int meson_dw_hdmi_bind(struct device *dev, struct device *master,
>  	if (IS_ERR(meson_dw_hdmi->hdmi))
>  		return PTR_ERR(meson_dw_hdmi->hdmi);
>  
> +	meson_dw_hdmi_init(meson_dw_hdmi);
> +
>  	next_bridge = of_drm_find_bridge(pdev->dev.of_node);
>  	if (next_bridge)
>  		drm_bridge_attach(encoder, next_bridge,
> 

Acked-by: Neil Armstrong <narmstrong@...libre.com>