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Date:   Wed, 20 Oct 2021 03:22:28 +0000
From:   Richard Zhu <hongxing.zhu@....com>
To:     Lucas Stach <l.stach@...gutronix.de>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>
CC:     "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>
Subject: RE: [RESEND v2 3/5] PCI: imx6: Fix the regulator dump when link never
 came up

> -----Original Message-----
> From: Richard Zhu
> Sent: Tuesday, October 19, 2021 3:40 PM
> To: Lucas Stach <l.stach@...gutronix.de>; bhelgaas@...gle.com;
> lorenzo.pieralisi@....com
> Cc: linux-pci@...r.kernel.org; dl-linux-imx <linux-imx@....com>;
> linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org;
> kernel@...gutronix.de
> Subject: RE: [RESEND v2 3/5] PCI: imx6: Fix the regulator dump when link
> never came up
> 
> > -----Original Message-----
> > From: Lucas Stach <l.stach@...gutronix.de>
> > Sent: Saturday, October 16, 2021 2:23 AM
> > To: Richard Zhu <hongxing.zhu@....com>; bhelgaas@...gle.com;
> > lorenzo.pieralisi@....com
> > Cc: linux-pci@...r.kernel.org; dl-linux-imx <linux-imx@....com>;
> > linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org;
> > kernel@...gutronix.de
> > Subject: Re: [RESEND v2 3/5] PCI: imx6: Fix the regulator dump when
> > link never came up
> >
> > Am Freitag, dem 15.10.2021 um 14:05 +0800 schrieb Richard Zhu:
> > > When PCIe PHY link never came up and vpcie regulator is present,
> > > there would be following dump when try to put the regulator.
> > > Disable this regulator to fix this dump when link never came up.
> > >
> > >   imx6q-pcie 33800000.pcie: Phy link never came up
> > >   imx6q-pcie: probe of 33800000.pcie failed with error -110
> > >   ------------[ cut here ]------------
> > >   WARNING: CPU: 3 PID: 119 at drivers/regulator/core.c:2256
> > _regulator_put.part.0+0x14c/0x158
> > >   Modules linked in:
> > >   CPU: 3 PID: 119 Comm: kworker/u8:2 Not tainted
> > 5.13.0-rc7-next-20210625-94710-ge4e92b2588a3 #10
> > >   Hardware name: FSL i.MX8MM EVK board (DT)
> > >   Workqueue: events_unbound async_run_entry_fn
> > >   pstate: 80000005 (Nzcv daif -PAN -UAO -TCO BTYPE=--)
> > >   pc : _regulator_put.part.0+0x14c/0x158
> > >   lr : regulator_put+0x34/0x48
> > >   sp : ffff8000122ebb30
> > >   x29: ffff8000122ebb30 x28: ffff800011be7000 x27:
> 0000000000000000
> > >   x26: 0000000000000000 x25: 0000000000000000 x24:
> ffff00000025f2bc
> > >   x23: ffff00000025f2c0 x22: ffff00000025f010 x21: ffff8000122ebc18
> > >   x20: ffff800011e3fa60 x19: ffff00000375fd80 x18: 0000000000000010
> > >   x17: 000000040044ffff x16: 00400032b5503510 x15:
> > 0000000000000108
> > >   x14: ffff0000003cc938 x13: 00000000ffffffea x12: 0000000000000000
> > >   x11: 0000000000000000 x10: ffff80001076ba88 x9 : ffff80001076a540
> > >   x8 : ffff00000025f2c0 x7 : ffff0000001f4450 x6 : ffff000000176cd8
> > >   x5 : ffff000003857880 x4 : 0000000000000000 x3 : ffff800011e3fe30
> > >   x2 : ffff0000003cc4c0 x1 : 0000000000000000 x0 : 0000000000000001
> > >   Call trace:
> > >    _regulator_put.part.0+0x14c/0x158
> > >    regulator_put+0x34/0x48
> > >    devm_regulator_release+0x10/0x18
> > >    release_nodes+0x38/0x60
> > >    devres_release_all+0x88/0xd0
> > >    really_probe+0xd0/0x2e8
> > >    __driver_probe_device+0x74/0xd8
> > >    driver_probe_device+0x7c/0x108
> > >    __device_attach_driver+0x8c/0xd0
> > >    bus_for_each_drv+0x74/0xc0
> > >    __device_attach_async_helper+0xb4/0xd8
> > >    async_run_entry_fn+0x30/0x100
> > >    process_one_work+0x19c/0x320
> > >    worker_thread+0x48/0x418
> > >    kthread+0x14c/0x158
> > >    ret_from_fork+0x10/0x18
> > >   ---[ end trace 3664ca4a50ce849b ]---
> > >
> > > Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> > > ---
> > >  drivers/pci/controller/dwc/pci-imx6.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > >
> > > diff --git a/drivers/pci/controller/dwc/pci-imx6.c
> > > b/drivers/pci/controller/dwc/pci-imx6.c
> > > index 3372775834a2..cc837f8bf6d4 100644
> > > --- a/drivers/pci/controller/dwc/pci-imx6.c
> > > +++ b/drivers/pci/controller/dwc/pci-imx6.c
> > > @@ -853,6 +853,8 @@ static int imx6_pcie_start_link(struct dw_pcie
> *pci)
> > >  		dw_pcie_readl_dbi(pci, PCIE_PORT_DEBUG0),
> > >  		dw_pcie_readl_dbi(pci, PCIE_PORT_DEBUG1));
> > >  	imx6_pcie_reset_phy(imx6_pcie);
> > > +	if (imx6_pcie->vpcie && regulator_is_enabled(imx6_pcie->vpcie) >
> 0)
> > > +		regulator_disable(imx6_pcie->vpcie);
> >
> > This doesn't seem like the right place to add this. I guess it would
> > be better to have proper error handling after dw_pcie_host_init to
> > roll back things like the clock and regulator enable.
> [Richard Zhu] This is good suggestion. It's make sense that move the regulator
> disable to the dw_pcie_host_init error handling since the regulator have the
> enabled check, before to disable it.
> But it seems that there are some potential problems when do the similar
> operations to the clocks disable here.
> Because that the dw_pcie_host_init might have some error returns when the
> host_init is not invoked at all.
> How to handle this situation although this is one corner case?
> 
[Richard Zhu] I have an idea to handle this case.
Add one more callback(e.x: host_exit() ) into dw_pcie_host_ops struct, then do the host_exit() when there is a error return after host_init() is invoked.
How about this solution?
I would send the v3 patch-set later if you don't say no to this method.

BR
Richard  

> Best Regards
> Richard Zhu
> >
> > Regards,
> > Lucas
> >
> > >  	return ret;
> > >  }
> > >
> >

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