From: JiSheng Teoh <jisheng.teoh@starfivetech.com>
To: Andi Shyti <andi.shyti@kernel.org>
Cc: Michal Simek <michal.simek@amd.com>,
Leyfoon Tan <leyfoon.tan@starfivetech.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-i2c@vger.kernel.org" <linux-i2c@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v2 RESEND] i2c: cadence: Add system suspend and resume PM support
Date: Mon, 22 Jan 2024 16:23:16 +0000 [thread overview]
Message-ID: <ZQ0PR01MB1160390D00404D24A31A1522EB75A@ZQ0PR01MB1160.CHNPR01.prod.partner.outlook.cn> (raw)
In-Reply-To: <ko44i4n5synf3uugp4wmjoe6eikyw3bzjtmarduwvskmk4d3dr@uewx27aa6ake>
Hi Andi,
>
> Hi Ji Sheng,
>
> I'm not fully conviced here.
>
> On Fri, Jan 19, 2024 at 09:33:26AM +0800, Ji Sheng Teoh wrote:
> > Enable device system suspend and resume PM support, and mark the
> > device state as suspended during system suspend to reject any data transfer.
> >
> > Signed-off-by: Ji Sheng Teoh <jisheng.teoh@starfivetech.com>
> > ---
> > Initial v2 was archived, previous discussion can be found in [1].
> > [1]:
> > https://lore.kernel.org/all/20231209131516.1916550-1-jisheng.teoh@star
> > fivetech.com/
> >
> > Changes since v1:
> > - Add missing err assignment in cdns_i2c_resume().
> > ---
> > drivers/i2c/busses/i2c-cadence.c | 33
> > ++++++++++++++++++++++++++++++++
> > 1 file changed, 33 insertions(+)
> >
> > diff --git a/drivers/i2c/busses/i2c-cadence.c
> > b/drivers/i2c/busses/i2c-cadence.c
> > index de3f58b60dce..4bb7d6756947 100644
> > --- a/drivers/i2c/busses/i2c-cadence.c
> > +++ b/drivers/i2c/busses/i2c-cadence.c
> > @@ -1176,6 +1176,18 @@ static int __maybe_unused cdns_i2c_runtime_suspend(struct device *dev)
> > return 0;
> > }
> >
> > +static int __maybe_unused cdns_i2c_suspend(struct device *dev) {
> > + struct cdns_i2c *xi2c = dev_get_drvdata(dev);
> > +
> > + i2c_mark_adapter_suspended(&xi2c->adap);
>
> this should go before the return '0' after checking that cdns_i2c_runtime_suspend(), even though we know it always returns '0', we
> still can use likely or unlikely.
>
Ok, that works for me. Will move it right before return '0', and append 'unlikely' to the runtime suspend check.
eg:
+if (unlikely(!pm_runtime_status_suspended(dev)))
+ cdns_i2c_runtime_suspend(dev);
+
+i2c_mark_adapter_suspended(&xi2c->adap);
+
+return 0;
> > + if (!pm_runtime_status_suspended(dev))
> > + return cdns_i2c_runtime_suspend(dev);
> > +
> > + return 0;
> > +}
> > +
> > /**
> > * cdns_i2c_init - Controller initialisation
> > * @id: Device private data structure
> > @@ -1219,7 +1231,28 @@ static int __maybe_unused cdns_i2c_runtime_resume(struct device *dev)
> > return 0;
> > }
> >
> > +static int __maybe_unused cdns_i2c_resume(struct device *dev) {
> > + struct cdns_i2c *xi2c = dev_get_drvdata(dev);
> > + int err;
> > +
> > + err = cdns_i2c_runtime_resume(dev);
> > + if (err)
> > + return err;
> > +
> > + if (pm_runtime_status_suspended(dev)) {
> > + err = cdns_i2c_runtime_suspend(dev);
> > + if (err)
> > + return err;
>
> We call the cdns_i2c_resume() functions to come up from a suspended state. But, if we fail to resume, we call the suspend and return
> '0' (because this always returns '0').
>
> In other words, if we take this path, we call resume, but we still end up suspended and return success.
>
> Andi
>
My understanding is that during system level resume 'cdns_i2c_resume()', the i2c device itself can still be held in runtime suspend regardless of the change in system level PM.
Looking back at this, we invoke cdns_i2c_runtime_resume() to enable clock and init the i2c device, the runtime PM state is still unchanged and kept suspended.
pm_runtime_status_suspended() will be evaluated as true, and runtime suspend 'cdns_i2c_runtime_suspend()' is invoked to disable the clock. This balances the clock count enabled earlier.
The runtime PM state is only resumed during cdns_i2c_master_xfer() through pm_runtime_resume_and_get(), and subsequently kept suspended through pm_runtime_put_autosuspend().
Since the cdns_i2c_runtime_suspend() always return '0', I will simplify them as follow:
+if (pm_runtime_status_suspended(dev))
+ cdns_i2c_runtime_suspend(dev);
> > + }
> > +
> > + i2c_mark_adapter_resumed(&xi2c->adap);
> > +
> > + return 0;
> > +}
> > +
> > static const struct dev_pm_ops cdns_i2c_dev_pm_ops = {
> > + SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(cdns_i2c_suspend, cdns_i2c_resume)
> > SET_RUNTIME_PM_OPS(cdns_i2c_runtime_suspend,
> > cdns_i2c_runtime_resume, NULL)
> > };
> > --
> > 2.43.0
> >
next prev parent reply other threads:[~2024-01-22 16:57 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-19 1:33 [PATCH v2 RESEND] i2c: cadence: Add system suspend and resume PM support Ji Sheng Teoh
2024-01-21 20:35 ` Andi Shyti
2024-01-22 16:23 ` JiSheng Teoh [this message]
2024-01-23 20:32 ` Andi Shyti
2024-01-24 4:46 ` JiSheng Teoh
2024-01-24 12:53 ` Andi Shyti
2024-01-25 15:30 ` JiSheng Teoh
2024-03-06 15:43 ` Andi Shyti
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