linux-kernel - Re: [PATCH 1/2] drm: bridge: dw-hdmi: Add hooks for suspend/resume

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Message-ID: <20190516101800.GE4995@pendragon.ideasonboard.com>
Date:   Thu, 16 May 2019 13:18:00 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     Heiko Stuebner <heiko@...ech.de>, Sandy Huang <hjc@...k-chips.com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        linux-rockchip@...ts.infradead.org,
        Neil Armstrong <narmstrong@...libre.com>, mka@...omium.org,
        Sean Paul <seanpaul@...omium.org>,
        Zheng Yang <zhengyang@...k-chips.com>,
        Sam Ravnborg <sam@...nborg.org>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Ville Syrjälä <ville.syrjala@...ux.intel.com>,
        David Airlie <airlied@...ux.ie>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH 1/2] drm: bridge: dw-hdmi: Add hooks for suspend/resume

Hi Douglas,

Thank you for the patch.

On Thu, May 02, 2019 at 03:38:07PM -0700, Douglas Anderson wrote:
> On Rockchip rk3288-based Chromebooks when you do a suspend/resume
> cycle:
> 
> 1. You lose the ability to detect an HDMI device being plugged in.
> 
> 2. If you're using the i2c bus built in to dw_hdmi then it stops
> working.
> 
> Let's add a hook to the core dw-hdmi driver so that we can call it in
> dw_hdmi-rockchip in the next commit.
> 
> NOTE: the exact set of steps I've done here in resume come from
> looking at the normal dw_hdmi init sequence in upstream Linux plus the
> sequence that we did in downstream Chrome OS 3.14.  Testing show that
> it seems to work, but if an extra step is needed or something here is
> not needed we could improve it.
> 
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
> 
>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 21 +++++++++++++++++++++
>  include/drm/bridge/dw_hdmi.h              |  3 +++
>  2 files changed, 24 insertions(+)
> 
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> index db761329a1e3..4b38bfd43e59 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -2780,6 +2780,27 @@ void dw_hdmi_unbind(struct dw_hdmi *hdmi)
>  }
>  EXPORT_SYMBOL_GPL(dw_hdmi_unbind);
>  
> +int dw_hdmi_suspend(struct dw_hdmi *hdmi)
> +{
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(dw_hdmi_suspend);
> +

As this is empty, should we leave it out ? It adds a bit of bloat to the
kernel for no real reason, and we can add it later if required.

> +int dw_hdmi_resume(struct dw_hdmi *hdmi)
> +{
> +	initialize_hdmi_ih_mutes(hdmi);
> +
> +	dw_hdmi_setup_i2c(hdmi);
> +	if (hdmi->i2c)
> +		dw_hdmi_i2c_init(hdmi);
> +
> +	if (hdmi->phy.ops->setup_hpd)
> +		hdmi->phy.ops->setup_hpd(hdmi, hdmi->phy.data);
> +
> +	return 0;

How about refactoring the probe function to extract hardware
initialisation to a separate function, and calling it from here ?

> +}
> +EXPORT_SYMBOL_GPL(dw_hdmi_resume);
> +
>  MODULE_AUTHOR("Sascha Hauer <s.hauer@...gutronix.de>");
>  MODULE_AUTHOR("Andy Yan <andy.yan@...k-chips.com>");
>  MODULE_AUTHOR("Yakir Yang <ykk@...k-chips.com>");
> diff --git a/include/drm/bridge/dw_hdmi.h b/include/drm/bridge/dw_hdmi.h
> index 66e70770cce5..c4132e9a5ae3 100644
> --- a/include/drm/bridge/dw_hdmi.h
> +++ b/include/drm/bridge/dw_hdmi.h
> @@ -154,6 +154,9 @@ struct dw_hdmi *dw_hdmi_bind(struct platform_device *pdev,
>  			     struct drm_encoder *encoder,
>  			     const struct dw_hdmi_plat_data *plat_data);
>  
> +int dw_hdmi_suspend(struct dw_hdmi *hdmi);
> +int dw_hdmi_resume(struct dw_hdmi *hdmi);
> +
>  void dw_hdmi_setup_rx_sense(struct dw_hdmi *hdmi, bool hpd, bool rx_sense);
>  
>  void dw_hdmi_set_sample_rate(struct dw_hdmi *hdmi, unsigned int rate);

-- 
Regards,

Laurent Pinchart