From mboxrd@z Thu Jan 1 00:00:00 1970 From: "xinhui.pan" Subject: Re: [PATCH] i2c-designware-pcidrv: fix the incorrect return of idle callback Date: Wed, 29 Jan 2014 18:00:26 +0800 Message-ID: <52E8D13A.1060100@intel.com> References: <52E744AC.2050606@intel.com> <20140128183035.GC20789@katana> <20140129083548.GG18029@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20140129083548.GG18029-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Mika Westerberg , Wolfram Sang Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org, yanmin_zhang-VuQAYsv1563Yd54FQh9/CA@public.gmane.org, bo.he-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org List-Id: linux-i2c@vger.kernel.org =E4=BA=8E 2014=E5=B9=B401=E6=9C=8829=E6=97=A5 16:35, Mika Westerberg =E5= =86=99=E9=81=93: > On Tue, Jan 28, 2014 at 07:30:35PM +0100, Wolfram Sang wrote: >> On Tue, Jan 28, 2014 at 01:48:28PM +0800, xinhui.pan wrote: >>> From: "xinhui.pan" >>> >>> i2c_dw_pci_runtime_idle should return -EBUSY rather than zero if it= do success. >> >> I don't understand... >> >>> Otherwise rpm_idle will call pm_suspend again and that may cause pm= _schedule_suspend delay invalidate. >>> =09 >>> Signed-off-by: bo.he >>> Signed-off-by: xinhui.pan >>> --- >>> drivers/i2c/busses/i2c-designware-pcidrv.c | 4 ++-- >>> 1 file changed, 2 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/i2c/busses/i2c-designware-pcidrv.c b/drivers/i= 2c/busses/i2c-designware-pcidrv.c >>> index f6ed06c..96e81f6 100644 >>> --- a/drivers/i2c/busses/i2c-designware-pcidrv.c >>> +++ b/drivers/i2c/busses/i2c-designware-pcidrv.c >>> @@ -190,8 +190,8 @@ static int i2c_dw_pci_runtime_idle(struct devic= e *dev) >>> int err =3D pm_schedule_suspend(dev, 500); >>> dev_dbg(dev, "runtime_idle called\n"); >>> =20 >>> - if (err !=3D 0) >>> - return 0; >>> + if (err) >>> + return err; >>> return -EBUSY; >> >> ... it does return EBUSY when pm_schedule_suspend() succeeds? It onl= y >> returns 0 if it does not succeed (for which I don't know if this is = an >> apropriate behaviour). Mika? >=20 > If I understand correctly, pm_schedule_suspend(dev, 500) is there bec= ause > we want to runtime suspend in 500 ms. It then returns -EBUSY to preve= nt PM > runtime from carrying on suspend on it's own. However, I have no idea= where > this magical 500 ms requirement comes from. >=20 > If we fail to schedule suspend we let the PM core to do whatever it t= hinks > suitable (in this case I suppose it suspends the device). >=20 Hi ,Mika If the callback returns 0,it means pm_schedule_suspend fails, also means rpm_check_suspend_allowed(pm_schedule_suspend calls it)=20 returns nonzero value.As a result,rpm_suspend will be called by rpm_idl= e. However in rpm_idle, rpm_check_suspend_allowed is called at first,too= =2E and the return value is treated as it is.But rpm_idle just returns=20 without doing anything(rpm_suspend is not called).=20 in both case above,why goes in different ways? I am confused. =20 > I think the whole idle dance could be replaced with a use of runtime = PM > autosuspend, just like we do in the platform version of the driver. >=20 > Xinghui, >=20 > Is this a real problem that you are trying to solve? >=20 To be honest,we got many panic when testing. But is not caused by this driver I think. while checking problems,we found these confusing codes by accident.