Re: [PATCH] omapdrm: hdmi4_cec: Fix CEC clock handling for PM

From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Tony Lindgren <tony@atomide.com>
Cc: Sebastian Reichel <sre@kernel.org>, Jyri Sarha <jsarha@ti.com>,
	Hans Verkuil <hverkuil@xs4all.nl>,
	Tomi Valkeinen <tomi.valkeinen@ti.com>,
	dri-devel@lists.freedesktop.org, linux-omap@vger.kernel.org
Subject: Re: [PATCH] omapdrm: hdmi4_cec: Fix CEC clock handling for PM
Date: Tue, 26 Mar 2019 04:21:13 +0200	[thread overview]
Message-ID: <20190326022113.GA25440@pendragon.ideasonboard.com> (raw)
In-Reply-To: <20190325234743.22529-1-tony@atomide.com>

Hi Tony,

Thank you for the patch.

On Mon, Mar 25, 2019 at 04:47:43PM -0700, Tony Lindgren wrote:
> If CONFIG_OMAP4_DSS_HDMI_CEC is enabled in .config, deeper SoC idle
> states are blocked because the CEC clock gets always enabled on init.
> 
> Let's fix the issue by moving the CEC clock handling to happen later in
> hdmi_cec_adap_enable() as suggested by Hans Verkuil <hverkuil@xs4all.nl>.
> This way the CEC clock gets only enabled when needed. This can be tested
> by doing cec-ctl --playback to enable the CEC, and doing cec-ctl --clear
> to disable it.
> 
> Let's also fix the typo for "divider" in the comments while at it.
> 
> Fixes: 8d7f934df8d8 ("omapdrm: hdmi4_cec: add OMAP4 HDMI CEC support")
> Suggested-by: Hans Verkuil <hverkuil@xs4all.nl>
> Cc: Hans Verkuil <hverkuil@xs4all.nl>
> Cc: Jyri Sarha <jsarha@ti.com>
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Signed-off-by: Tony Lindgren <tony@atomide.com>

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> ---
>  drivers/gpu/drm/omapdrm/dss/hdmi4_cec.c | 16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/omapdrm/dss/hdmi4_cec.c b/drivers/gpu/drm/omapdrm/dss/hdmi4_cec.c
> --- a/drivers/gpu/drm/omapdrm/dss/hdmi4_cec.c
> +++ b/drivers/gpu/drm/omapdrm/dss/hdmi4_cec.c
> @@ -169,12 +169,19 @@ static int hdmi_cec_adap_enable(struct cec_adapter *adap, bool enable)
>  	struct hdmi_core_data *core = cec_get_drvdata(adap);
>  	int temp, err;
>  
> -	if (!enable) {
> +	if (enable) {
> +		/*
> +		 * Initialize CEC clock divider: CEC needs 2MHz clock hence
> +		 * set the divider to 24 to get 48/24=2MHz clock
> +		 */
> +		REG_FLD_MOD(core->wp->base, HDMI_WP_CLK, 0x18, 5, 0);
> +	} else {
>  		hdmi_write_reg(core->base, HDMI_CEC_INT_ENABLE_0, 0);
>  		hdmi_write_reg(core->base, HDMI_CEC_INT_ENABLE_1, 0);
>  		REG_FLD_MOD(core->base, HDMI_CORE_SYS_INTR_UNMASK4, 0, 3, 3);
>  		hdmi_wp_clear_irqenable(core->wp, HDMI_IRQ_CORE);
>  		hdmi_wp_set_irqstatus(core->wp, HDMI_IRQ_CORE);
> +		REG_FLD_MOD(core->wp->base, HDMI_WP_CLK, 0, 5, 0);
>  		hdmi4_core_disable(core);
>  		return 0;
>  	}
> @@ -333,11 +340,8 @@ int hdmi4_cec_init(struct platform_device *pdev, struct hdmi_core_data *core,
>  		return ret;
>  	core->wp = wp;
>  
> -	/*
> -	 * Initialize CEC clock divider: CEC needs 2MHz clock hence
> -	 * set the devider to 24 to get 48/24=2MHz clock
> -	 */
> -	REG_FLD_MOD(core->wp->base, HDMI_WP_CLK, 0x18, 5, 0);
> +	/* Disable clock initially, hdmi_cec_adap_enable() manages it */
> +	REG_FLD_MOD(core->wp->base, HDMI_WP_CLK, 0, 5, 0);
>  
>  	ret = cec_register_adapter(core->adap, &pdev->dev);
>  	if (ret < 0) {

-- 
Regards,

Laurent Pinchart
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