linux-kernel - Re: [PATCH v7 12/13] slimbus: qcom: Add runtime-pm support using clock-pause

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Message-ID: <20171123101749.ojiv6l52jjq6b55b@localhost.localdomain>
Date:   Thu, 23 Nov 2017 10:17:49 +0000
From:   Charles Keepax <ckeepax@...nsource.cirrus.com>
To:     <srinivas.kandagatla@...aro.org>
CC:     <gregkh@...uxfoundation.org>, <broonie@...nel.org>,
        <alsa-devel@...a-project.org>, <sdharia@...eaurora.org>,
        <bp@...e.de>, <poeschel@...onage.de>, <treding@...dia.com>,
        <andreas.noever@...il.com>, <alan@...ux.intel.com>,
        <mathieu.poirier@...aro.org>, <daniel@...ll.ch>, <jkosina@...e.cz>,
        <sharon.dvir1@...l.huji.ac.il>, <joe@...ches.com>,
        <davem@...emloft.net>, <james.hogan@...tec.com>,
        <michael.opdenacker@...e-electrons.com>, <robh+dt@...nel.org>,
        <pawel.moll@....com>, <mark.rutland@....com>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>, <vinod.koul@...el.com>,
        <arnd@...db.de>
Subject: Re: [PATCH v7 12/13] slimbus: qcom: Add runtime-pm support using
 clock-pause

On Wed, Nov 15, 2017 at 02:10:42PM +0000, srinivas.kandagatla@...aro.org wrote:
> From: Sagar Dharia <sdharia@...eaurora.org>
> 
> Slimbus HW mandates that clock-pause sequence has to be executed
> before disabling relevant interface and core clocks.
> Runtime-PM's autosuspend feature is used here to enter/exit low
> power mode for Qualcomm's Slimbus controller. Autosuspend feature
> enables driver to avoid changing power-modes too frequently since
> entering clock-pause is an expensive sequence
> 
> Signed-off-by: Sagar Dharia <sdharia@...eaurora.org>
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
> ---
> +
> +#ifdef CONFIG_PM_SLEEP
> +static int qcom_slim_suspend(struct device *dev)
> +{
> +	int ret = 0;
> +
> +	if (!pm_runtime_enabled(dev) ||
> +		(!pm_runtime_suspended(dev))) {
> +		dev_dbg(dev, "system suspend");
> +		ret = qcom_slim_runtime_suspend(dev);
> +	}
> +
> +	/*
> +	 * If the clock pause failed due to active channels, there is
> +	 * a possibility that some audio stream is active during suspend.
> +	 * (e.g. modem usecase during suspend)
> +	 * We dont want to return suspend failure in that case so that
> +	 * display and relevant components can still go to suspend.
> +	 * If there is some other error, then it should prevent
> +	 * system level suspend
> +	 */
> +	if (ret == -EISCONN)
> +		ret = 0;

Who actually returns the EISCONN for this to catch? Or will that
be added to slim_ctrl_clk_pause once support for the audio
channels is added?

Thanks,
Charles

> +
> +	return ret;
> +}