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Message-ID: <07e66b114b764211b8f04b4c53462181@BY2FFO11FD046.protection.gbl>
Date: Tue, 13 Jan 2015 10:43:54 -0800
From: Sören Brinkmann <soren.brinkmann@...inx.com>
To: Marc Kleine-Budde <mkl@...gutronix.de>
CC: Kedareswara rao Appana <appana.durga.rao@...inx.com>,
<wg@...ndegger.com>, <michal.simek@...inx.com>,
<grant.likely@...aro.org>, <robh+dt@...nel.org>,
<linux-can@...r.kernel.org>, <netdev@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
Kedareswara rao Appana <appanad@...inx.com>
Subject: Re: [PATCH v5] can: Convert to runtime_pm
On Tue, 2015-01-13 at 07:03PM +0100, Marc Kleine-Budde wrote:
> On 01/13/2015 06:49 PM, Sören Brinkmann wrote:
> > On Tue, 2015-01-13 at 06:44PM +0100, Marc Kleine-Budde wrote:
> >> On 01/13/2015 06:24 PM, Sören Brinkmann wrote:
> >>> On Tue, 2015-01-13 at 06:17PM +0100, Marc Kleine-Budde wrote:
> >>>> On 01/13/2015 06:08 PM, Sören Brinkmann wrote:
> >>>>> On Tue, 2015-01-13 at 12:08PM +0100, Marc Kleine-Budde wrote:
> >>>>>> On 01/12/2015 07:45 PM, Sören Brinkmann wrote:
> >>>>>>> On Mon, 2015-01-12 at 08:34PM +0530, Kedareswara rao Appana wrote:
> >>>>>>>> Instead of enabling/disabling clocks at several locations in the driver,
> >>>>>>>> Use the runtime_pm framework. This consolidates the actions for runtime PM
> >>>>>>>> In the appropriate callbacks and makes the driver more readable and mantainable.
> >>>>>>>>
> >>>>>>>> Signed-off-by: Soren Brinkmann <soren.brinkmann@...inx.com>
> >>>>>>>> Signed-off-by: Kedareswara rao Appana <appanad@...inx.com>
> >>>>>>>> ---
> >>>>>>>> Changes for v5:
> >>>>>>>> - Updated with the review comments.
> >>>>>>>> Updated the remove fuction to use runtime_pm.
> >>>>>>>> Chnages for v4:
> >>>>>>>> - Updated with the review comments.
> >>>>>>>> Changes for v3:
> >>>>>>>> - Converted the driver to use runtime_pm.
> >>>>>>>> Changes for v2:
> >>>>>>>> - Removed the struct platform_device* from suspend/resume
> >>>>>>>> as suggest by Lothar.
> >>>>>>>>
> >>>>>>>> drivers/net/can/xilinx_can.c | 157 ++++++++++++++++++++++++++++-------------
> >>>>>>>> 1 files changed, 107 insertions(+), 50 deletions(-)
> >>>>>>> [..]
> >>>>>>>> +static int __maybe_unused xcan_runtime_resume(struct device *dev)
> >>>>>>>> {
> >>>>>>>> - struct platform_device *pdev = dev_get_drvdata(dev);
> >>>>>>>> - struct net_device *ndev = platform_get_drvdata(pdev);
> >>>>>>>> + struct net_device *ndev = dev_get_drvdata(dev);
> >>>>>>>> struct xcan_priv *priv = netdev_priv(ndev);
> >>>>>>>> int ret;
> >>>>>>>> + u32 isr, status;
> >>>>>>>>
> >>>>>>>> ret = clk_enable(priv->bus_clk);
> >>>>>>>> if (ret) {
> >>>>>>>> @@ -1014,15 +1030,28 @@ static int __maybe_unused xcan_resume(struct device *dev)
> >>>>>>>> ret = clk_enable(priv->can_clk);
> >>>>>>>> if (ret) {
> >>>>>>>> dev_err(dev, "Cannot enable clock.\n");
> >>>>>>>> - clk_disable_unprepare(priv->bus_clk);
> >>>>>>>> + clk_disable(priv->bus_clk);
> >>>>>>> [...]
> >>>>>>>> @@ -1173,12 +1219,23 @@ static int xcan_remove(struct platform_device *pdev)
> >>>>>>>> {
> >>>>>>>> struct net_device *ndev = platform_get_drvdata(pdev);
> >>>>>>>> struct xcan_priv *priv = netdev_priv(ndev);
> >>>>>>>> + int ret;
> >>>>>>>> +
> >>>>>>>> + ret = pm_runtime_get_sync(&pdev->dev);
> >>>>>>>> + if (ret < 0) {
> >>>>>>>> + netdev_err(ndev, "%s: pm_runtime_get failed(%d)\n",
> >>>>>>>> + __func__, ret);
> >>>>>>>> + return ret;
> >>>>>>>> + }
> >>>>>>>>
> >>>>>>>> if (set_reset_mode(ndev) < 0)
> >>>>>>>> netdev_err(ndev, "mode resetting failed!\n");
> >>>>>>>>
> >>>>>>>> unregister_candev(ndev);
> >>>>>>>> + pm_runtime_disable(&pdev->dev);
> >>>>>>>> netif_napi_del(&priv->napi);
> >>>>>>>> + clk_disable_unprepare(priv->bus_clk);
> >>>>>>>> + clk_disable_unprepare(priv->can_clk);
> >>>>>>>
> >>>>>>> Shouldn't pretty much all these occurrences of clk_disable/enable
> >>>>>>> disappear? This should all be handled by the runtime_pm framework now.
> >>>>>>
> >>>>>> We have:
> >>>>>> - clk_prepare_enable() in probe
> >>>>>
> >>>>> This should become something like pm_runtime_get_sync(), shouldn't it?
> >>>>>
> >>>>>> - clk_disable_unprepare() in remove
> >>>>>
> >>>>> pm_runtime_put()
> >>>>>
> >>>>>> - clk_enable() in runtime_resume
> >>>>>> - clk_disable() in runtime_suspend
> >>>>>
> >>>>> These are the ones needed.
> >>>>>
> >>>>> The above makes me suspect that the clocks are always on, regardless of
> >>>>
> >>>> Define "on" :)
> >>>> The clocks are prepared after probe() exists, but not enabled. The first
> >>>> pm_runtime_get_sync() will enable the clocks.
> >>>>
> >>>>> the runtime suspend state since they are enabled in probe and disabled
> >>>>> in remove, is that right? Ideally, the usage in probe and remove should
> >>>>> be migrated to runtime_pm and clocks should really only be running when
> >>>>> needed and not throughout the whole lifetime of the driver.
> >>>>
> >>>> The clocks are not en/disabled via pm_runtime, because
> >>>> pm_runtime_get_sync() is called from atomic contect. We can have another
> >>>> look into the driver and try to change this.
> >>
> >>> Wasn't that why the call to pm_runtime_irq_safe() was added?
> >>
> >> Good question. That should be investigated.
> >>
> >>> Also, clk_enable/disable should be okay to be run from atomic context.
> >>> And if the clock are already prepared after the exit of probe that
> >>> should be enough. Then remove() should just have to do the unprepare.
> >>> But I don't see why runtime_pm shouldn't be able to do the
> >>> enable/disable.
> >>
> >> runtime_pm does call the clk_{enable,disable} function. But you mean
> >> clk_prepare() + pm_runtime_get_sync() should be used in probe() instead
> >> of calling clk_prepare_enable(). Good idea! I think the
> >> "pm_runtime_set_active(&pdev->dev);" has to be removed from the patch.
> >
> > Right, that's what I was thinking. The proposed changes make sense, IMHO.
> >
> >>
> >> Coming back whether blocking calls are allowed or not.
> >> If you make a call to pm_runtime_irq_safe(), you state that it's okay to
> >> call pm_runtime_get_sync() from atomic context. But it's only called in
> >> open, probe, remove and in xcan_get_berr_counter, which is not called
> >> from atomic either. So let's try to remove the pm_runtime_irq_safe() and
> >> use clk_prepare_enable() clk_disable_unprepare() in the runtime_resume()
> >> runtime_suspend() functions.
> >
> > IIRC, xcan_get_berr_counter() is called from atomic context. I think
> > that was how this got started.
>
> In some drivers the get_berr_counter() function is used in the irq
> handler, but here it's only called from outside, an thus from non atomic
> context.
>
> From an older mail of yours:
>
> > I have the feeling I'm missing something. If I remove the 'must not
> > sleep' requirement from the runtime suspend/resume functions, I get
> > this:
> >
> > BUG: sleeping function called from invalid context at drivers/base/power/runtime.c:954
>
> http://lxr.free-electrons.com/source/drivers/base/power/runtime.c#L954
>
> I think it's failing because of the pm_runtime_irq_safe() call.
Adding that call fixed this issue.
Sören
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