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

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Date:   Sat, 7 Oct 2017 11:25:12 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Jonathan Neuschäfer <j.neuschaefer@....net>
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

Thanks for the review comments

On 07/10/17 09:22, Jonathan Neuschäfer wrote:
> 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.
Yep I agree will fix all such instances.

> 
>> +	 * 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.
Yep. will fix this too.

> 
>> +	 * 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
>