Date:   Fri, 13 Jul 2018 15:24:01 -0700
From:   Evan Green <evgreen@...omium.org>
To:     Karthikeyan Ramasubramanian <kramasub@...eaurora.org>
Cc:     Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        swboyd@...omium.org, Doug Anderson <dianders@...omium.org>,
        Girish Mahadevan <girishm@...eaurora.org>,
        linux-i2c@...r.kernel.org
Subject: Re: [PATCH] i2c: i2c-qcom-geni: Fix suspend clock handling

On Fri, Jul 13, 2018 at 3:21 PM Karthik Ramasubramanian
<kramasub@...eaurora.org> wrote:
>
>
>
> On 7/9/2018 5:49 PM, Evan Green wrote:
> > pm_runtime_suspended can return 0 even if the last runtime power
> > management function called in the device was a suspend call. This
> > trips up the i2c-qcom-geni's suspend_noirq accounting, which was
> > trying to use the function to determine if it should disable clocks
> > or if that had already been done.
> >
> > The fix is to track whether or not clocks have been enabled explicitly
> > in the driver with a new member. While in there, also honor the return
> > value of geni_se_resources_off, which can technically fail.
> >
> > An example of the warning generated during suspend:
> > [   68.314733] WARNING: CPU: 0 PID: 1990 at drivers/clk/clk.c:595 clk_core_disable+0x28/0x200
> > [   68.464576] Call trace:
> > [   68.554410] [<ffffff80083f0ed0>] clk_core_disable+0x28/0x200
> > [   68.560244] [<ffffff80083f349c>] clk_disable+0x38/0x4c
> > [   68.565541] [<ffffff8008408910>] geni_se_resources_off+0x40/0x74
> > [   68.571731] [<ffffff800862aadc>] geni_i2c_runtime_suspend+0x2c/0x3c
> > [   68.578185] [<ffffff800862ae6c>] geni_i2c_suspend_noirq+0x38/0x68
> > [   68.584475] [<ffffff800852bd40>] dpm_run_callback+0x104/0x210
> > [   68.590404] [<ffffff800852c3d4>] __device_suspend_noirq+0x158/0x1a8
> > [   68.596859] [<ffffff800852dff0>] dpm_noirq_suspend_devices+0x180/0x38c
> > [   68.603594] [<ffffff80080fdebc>] suspend_devices_and_enter+0x49c/0x964
> > [   68.610321] [<ffffff80080fea14>] pm_suspend+0x690/0x6e0
> > [   68.615712] [<ffffff80080fc930>] state_store+0xd4/0xf8
> > [   68.621014] [<ffffff80088a57f0>] kobj_attr_store+0x18/0x28
> > [   68.626672] [<ffffff8008297a54>] sysfs_kf_write+0x5c/0x68
> > [   68.632240] [<ffffff8008296a00>] kernfs_fop_write+0x174/0x1b8
> > [   68.638177] [<ffffff800821a2c4>] __vfs_write+0x58/0x160
> > [   68.643567] [<ffffff800821a5d8>] vfs_write+0xcc/0x184
> > [   68.648780] [<ffffff800821a850>] SyS_write+0x64/0xb4
> >
> > Signed-off-by: Evan Green <evgreen@...omium.org>
> > ---
> > This change applies atop Karthik's patch [1], which as far as I can tell
> > technically hasn't landed yet, but also hasn't had feedback in awhile
> > either. I opted to submit this as a separate patch, but if the maintainers
> > prefer it's fine with me if this get folded in to another spin of the
> > base series.
> >
> > [1] https://patchwork.kernel.org/patch/10460819/
> >
> >  drivers/i2c/busses/i2c-qcom-geni.c | 25 ++++++++++++++++++++++---
> >  1 file changed, 22 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
> > index 54bcd1a79cc5..90c4cbfa22d8 100644
> > --- a/drivers/i2c/busses/i2c-qcom-geni.c
> > +++ b/drivers/i2c/busses/i2c-qcom-geni.c
> > @@ -85,6 +85,7 @@ struct geni_i2c_dev {
> >       spinlock_t lock;
> >       u32 clk_freq_out;
> >       const struct geni_i2c_clk_fld *clk_fld;
> > +     int suspended;
> >  };
> >
> >  struct geni_i2c_err_log {
> > @@ -567,9 +568,15 @@ static int geni_i2c_probe(struct platform_device *pdev)
> >       geni_se_init(&gi2c->se, gi2c->tx_wm, tx_depth);
> >       geni_se_config_packing(&gi2c->se, BITS_PER_BYTE, PACKING_BYTES_PW,
> >                                                       true, true, true);
> > -     geni_se_resources_off(&gi2c->se);
> > +     ret = geni_se_resources_off(&gi2c->se);
> > +     if (ret) {
> > +             dev_err(&pdev->dev, "Error turning off resources %d\n", ret);
> > +             return ret;
> > +     }
> > +
> >       dev_dbg(&pdev->dev, "i2c fifo/se-dma mode. fifo depth:%d\n", tx_depth);
> >
> > +     gi2c->suspended = 1;
> >       pm_runtime_set_suspended(gi2c->se.dev);
> >       pm_runtime_set_autosuspend_delay(gi2c->se.dev, I2C_AUTO_SUSPEND_DELAY);
> >       pm_runtime_use_autosuspend(gi2c->se.dev);
> > @@ -590,10 +597,19 @@ static int geni_i2c_remove(struct platform_device *pdev)
> >
> >  static int __maybe_unused geni_i2c_runtime_suspend(struct device *dev)
> >  {
> > +     int ret;
> >       struct geni_i2c_dev *gi2c = dev_get_drvdata(dev);
> >
> >       disable_irq(gi2c->irq);
> > -     geni_se_resources_off(&gi2c->se);
> > +     ret = geni_se_resources_off(&gi2c->se);
> > +     if (ret) {
> > +             enable_irq(gi2c->irq);
> > +             return ret;
> > +
> > +     } else {
> > +             gi2c->suspended = 1;
> > +     }
> > +
> >       return 0;
> >  }
> >
> > @@ -607,12 +623,15 @@ static int __maybe_unused geni_i2c_runtime_resume(struct device *dev)
> >               return ret;
> >
> >       enable_irq(gi2c->irq);
> > +     gi2c->suspended = 0;
> >       return 0;
> >  }
> >
> >  static int __maybe_unused geni_i2c_suspend_noirq(struct device *dev)
> >  {
> > -     if (!pm_runtime_suspended(dev)) {
> > +     struct geni_i2c_dev *gi2c = dev_get_drvdata(dev);
> > +
> > +     if (!gi2c->suspended) {
> >               geni_i2c_runtime_suspend(dev);
> >               pm_runtime_disable(dev);
> >               pm_runtime_set_suspended(dev);
> >
> Reviewed-by: Karthikeyan Ramasubramanian <kramasub@...eaurora.org>

Sounds good to me, Wolfram. Thanks for the review, Karthik.
-Evan

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