linux-kernel - Re: [Patch v6 5/7] slimbus: qcom: Add runtime-pm support using clock-pause feature

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Message-ID: <20171007082259.kumlkus5mg5eh5cr@latitude>
Date:   Sat, 7 Oct 2017 10:22:59 +0200
From:   Jonathan Neuschäfer <j.neuschaefer@....net>
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,
        gong.chen@...ux.intel.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,
        kheitke@...ience.com, linux-arm-msm@...r.kernel.org, arnd@...db.de
Subject: Re: [Patch v6 5/7] slimbus: qcom: Add runtime-pm support using
 clock-pause feature

Hi, some more trivial comments below.

On Fri, Oct 06, 2017 at 05:51:34PM +0200, 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>
> ---
[...]
> +static int msm_clk_pause_wakeup(struct slim_controller *ctrl)
> +{
> +	struct msm_slim_ctrl *dev = slim_get_ctrldata(ctrl);
> +
> +	clk_prepare_enable(dev->hclk);
> +	clk_prepare_enable(dev->rclk);
> +	enable_irq(dev->irq);
> +
> +	writel_relaxed(1, dev->base + FRM_WAKEUP);
> +	/* Make sure framer wakeup write goes through before ISR fires */
> +	mb();
> +	/**

This isn't really a kerneldoc comment.

> +	 * HW Workaround: Currently, slave is reporting lost-sync messages
> +	 * after slimbus comes out of clock pause.
> +	 * Transaction with slave fail before slave reports that message
> +	 * Give some time for that report to come
> +	 * Slimbus wakes up in clock gear 10 at 24.576MHz. With each superframe
> +	 * being 250 usecs, we wait for 5-10 superframes here to ensure
> +	 * we get the message
> +	 */
> +	usleep_range(1250, 2500);
> +	return 0;
> +}
[...]
> +#ifdef CONFIG_PM_SLEEP
> +static int msm_slim_suspend(struct device *dev)
> +{
> +	int ret = 0;
> +
> +	if (!pm_runtime_enabled(dev) ||
> +		(!pm_runtime_suspended(dev))) {
> +		dev_dbg(dev, "system suspend");
> +		ret = msm_slim_runtime_suspend(dev);
> +	}
> +	if (ret == -EISCONN) {
> +	/**

ditto.
Also, it looks misindented.

> +	 * 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
> +	 */
> +		ret = 0;
> +	}
> +	return ret;
> +}


Thanks,
Jonathan Neuschäfer

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