RE: [RESEND v2 3/5] PCI: imx6: Fix the regulator dump when link never came up

[Richard Zhu <hongxing.zhu@nxp.com>]

> -----Original Message-----
> From: Lucas Stach <l.stach@pengutronix.de>
> Sent: Saturday, October 16, 2021 2:23 AM
> To: Richard Zhu <hongxing.zhu@nxp.com>; bhelgaas@google.com;
> lorenzo.pieralisi@arm.com
> Cc: linux-pci@vger.kernel.org; dl-linux-imx <linux-imx@nxp.com>;
> linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org;
> kernel@pengutronix.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@nxp.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?

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

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