linux-kernel - Re: [PATCH v2 1/5] drm: bridge: dw_hdmi: cec: Add cec suspend/resume function

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Date:   Fri, 8 Apr 2022 15:41:36 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Sandor Yu <Sandor.yu@....com>, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, andrzej.hajda@...el.com,
        robert.foss@...aro.org, Laurent.pinchart@...asonboard.com,
        jonas@...boo.se, jernej.skrabec@...il.com, hverkuil-cisco@...all.nl
Cc:     shengjiu.wang@....com, cai.huoqing@...ux.dev, maxime@...no.tech,
        harry.wentland@....com
Subject: Re: [PATCH v2 1/5] drm: bridge: dw_hdmi: cec: Add cec suspend/resume
 function

On 08/04/2022 12:32, Sandor Yu wrote:
> CEC interrupt status/mask and logical address registers
> will be reset when device enter suspend.
> It will cause cec fail to work after device resume.
> Add CEC suspend/resume functions, reinitialize logical address registers
> and restore interrupt status/mask registers after resume.
> 
> Signed-off-by: Sandor Yu <Sandor.yu@....com>
> ---
>   drivers/gpu/drm/bridge/synopsys/dw-hdmi-cec.c | 37 +++++++++++++++++++
>   1 file changed, 37 insertions(+)
> 
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-cec.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-cec.c
> index c8f44bcb298a..ab176401b727 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-cec.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-cec.c
> @@ -62,6 +62,10 @@ struct dw_hdmi_cec {
>   	bool rx_done;
>   	struct cec_notifier *notify;
>   	int irq;
> +
> +	u8 regs_polarity;
> +	u8 regs_mask;
> +	u8 regs_mute_stat0;
>   };
>   
>   static void dw_hdmi_write(struct dw_hdmi_cec *cec, u8 val, int offset)
> @@ -306,11 +310,44 @@ static int dw_hdmi_cec_remove(struct platform_device *pdev)
>   	return 0;
>   }
>   
> +static int __maybe_unused dw_hdmi_cec_resume(struct device *dev)
> +{
> +	struct dw_hdmi_cec *cec = dev_get_drvdata(dev);
> +
> +	/* Restore logical address */
> +	dw_hdmi_write(cec, cec->addresses & 255, HDMI_CEC_ADDR_L);
> +	dw_hdmi_write(cec, cec->addresses >> 8, HDMI_CEC_ADDR_H);
> +
> +	/* Restore interrupt status/mask register */
> +	dw_hdmi_write(cec, cec->regs_polarity, HDMI_CEC_POLARITY);
> +	dw_hdmi_write(cec, cec->regs_mask, HDMI_CEC_MASK);
> +	dw_hdmi_write(cec, cec->regs_mute_stat0, HDMI_IH_MUTE_CEC_STAT0);
> +
> +	return 0;
> +}
> +
> +static int __maybe_unused dw_hdmi_cec_suspend(struct device *dev)
> +{
> +	struct dw_hdmi_cec *cec = dev_get_drvdata(dev);
> +
> +	/* store interrupt status/mask register */
> +	 cec->regs_polarity = dw_hdmi_read(cec, HDMI_CEC_POLARITY);
> +	 cec->regs_mask = dw_hdmi_read(cec, HDMI_CEC_MASK);
> +	 cec->regs_mute_stat0 = dw_hdmi_read(cec, HDMI_IH_MUTE_CEC_STAT0);
> +
> +	return 0;
> +}
> +
> +static const struct dev_pm_ops dw_hdmi_cec_pm = {
> +	SET_SYSTEM_SLEEP_PM_OPS(dw_hdmi_cec_suspend, dw_hdmi_cec_resume)
> +};
> +
>   static struct platform_driver dw_hdmi_cec_driver = {
>   	.probe	= dw_hdmi_cec_probe,
>   	.remove	= dw_hdmi_cec_remove,
>   	.driver = {
>   		.name = "dw-hdmi-cec",
> +		.pm = &dw_hdmi_cec_pm,
>   	},
>   };
>   module_platform_driver(dw_hdmi_cec_driver);

As Hans said on v1, why don't you call dw_hdmi_cec_enable(cec->adap, false) in suspend and dw_hdmi_cec_enable(cec->adap, true) in resume ?

With this, CEC engine is not disabled on suspend.

Do you plan to use the engine from the suspend code ?

Neil