linux-kernel - RE: [PATCH v1] PCI: imx6: Set MSI enable bit of RC in resume

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Date:   Mon, 28 Nov 2022 03:45:30 +0000
From:   Hongxing 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>,
        "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>,
        dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH v1] PCI: imx6: Set MSI enable bit of RC in resume

> -----Original Message-----
> From: Lucas Stach <l.stach@...gutronix.de>
> Sent: 2022年11月25日 18:19
> To: Hongxing Zhu <hongxing.zhu@....com>; bhelgaas@...gle.com;
> lorenzo.pieralisi@....com
> Cc: linux-pci@...r.kernel.org; linux-arm-kernel@...ts.infradead.org;
> linux-kernel@...r.kernel.org; kernel@...gutronix.de; dl-linux-imx
> <linux-imx@....com>
> Subject: Re: [PATCH v1] PCI: imx6: Set MSI enable bit of RC in resume
> 
> Am Freitag, dem 25.11.2022 um 02:07 +0000 schrieb Hongxing Zhu:
> > Friendly ping.
> > Anymore comments are very appreciated.
> >
> > BTW, I had verified on i.MX7D/i.MX6QP platforms that MSI wouldn’t be
> > functional  after resume without this patch.
> 
> Instead of playing whack-a-mole and restoring individual config setting after
> resume, shouldn't we just do a pci_save_state() on suspend and then restore
> the complete config by calling pci_restore_state() on resume?
> 
Hi Lucas:
Thanks for your comments.
Refer to my understanding, only the i.MX PCIe specific configs that might
 be lost during suspend/resume should be saved/restored here.

Because that most of the configs had been re-configured in the
 suspend/resume paths already.
So, only the PCI_MSI_FLAGS should be saved/restored here, right?

Best Regards
Richard Zhu

> Regards,
> Lucas
> 
> >
> > Best Regards
> > Richard Zhu
> >
> > > -----Original Message-----
> > > From: Richard Zhu <hongxing.zhu@....com>
> > > Sent: 2022年11月1日 16:00
> > > To: l.stach@...gutronix.de; bhelgaas@...gle.com;
> > > lorenzo.pieralisi@....com
> > > Cc: Hongxing Zhu <hongxing.zhu@....com>; linux-pci@...r.kernel.org;
> > > linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org;
> > > kernel@...gutronix.de; dl-linux-imx <linux-imx@....com>
> > > Subject: [PATCH v1] PCI: imx6: Set MSI enable bit of RC in resume
> > >
> > > The MSI Enable bit controls delivery of MSI interrupts from
> > > components below the Root Port. This bit might lost during the
> > > suspend, should be re-configured during resume.
> > >
> > > Encapsulate the MSI enable set into a standalone function, and
> > > invoke it in both probe and resume.
> > >
> > > Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> > > ---
> > >  drivers/pci/controller/dwc/pci-imx6.c | 24 +++++++++++++++++-------
> > >  1 file changed, 17 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/drivers/pci/controller/dwc/pci-imx6.c
> > > b/drivers/pci/controller/dwc/pci-imx6.c
> > > index 2616585ca5f8..dba15546075f 100644
> > > --- a/drivers/pci/controller/dwc/pci-imx6.c
> > > +++ b/drivers/pci/controller/dwc/pci-imx6.c
> > > @@ -1041,6 +1041,21 @@ static void imx6_pcie_pm_turnoff(struct
> > > imx6_pcie *imx6_pcie)
> > >  	usleep_range(1000, 10000);
> > >  }
> > >
> > > +static void pci_imx_set_msi_en(struct dw_pcie *pci) {
> > > +	u8 offset;
> > > +	u16 val;
> > > +
> > > +	if (pci_msi_enabled()) {
> > > +		offset = dw_pcie_find_capability(pci, PCI_CAP_ID_MSI);
> > > +		dw_pcie_dbi_ro_wr_en(pci);
> > > +		val = dw_pcie_readw_dbi(pci, offset + PCI_MSI_FLAGS);
> > > +		val |= PCI_MSI_FLAGS_ENABLE;
> > > +		dw_pcie_writew_dbi(pci, offset + PCI_MSI_FLAGS, val);
> > > +		dw_pcie_dbi_ro_wr_dis(pci);
> > > +	}
> > > +}
> > > +
> > >  static int imx6_pcie_suspend_noirq(struct device *dev)  {
> > >  	struct imx6_pcie *imx6_pcie = dev_get_drvdata(dev); @@ -1073,6
> > > +1088,7 @@ static int imx6_pcie_resume_noirq(struct device *dev)
> > >  	if (imx6_pcie->link_is_up)
> > >  		imx6_pcie_start_link(imx6_pcie->pci);
> > >
> > > +	pci_imx_set_msi_en(imx6_pcie->pci);
> > >  	return 0;
> > >  }
> > >
> > > @@ -1090,7 +1106,6 @@ static int imx6_pcie_probe(struct
> > > platform_device
> > > *pdev)
> > >  	struct resource *dbi_base;
> > >  	struct device_node *node = dev->of_node;
> > >  	int ret;
> > > -	u16 val;
> > >
> > >  	imx6_pcie = devm_kzalloc(dev, sizeof(*imx6_pcie), GFP_KERNEL);
> > >  	if (!imx6_pcie)
> > > @@ -1282,12 +1297,7 @@ static int imx6_pcie_probe(struct
> > > platform_device
> > > *pdev)
> > >  	if (ret < 0)
> > >  		return ret;
> > >
> > > -	if (pci_msi_enabled()) {
> > > -		u8 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_MSI);
> > > -		val = dw_pcie_readw_dbi(pci, offset + PCI_MSI_FLAGS);
> > > -		val |= PCI_MSI_FLAGS_ENABLE;
> > > -		dw_pcie_writew_dbi(pci, offset + PCI_MSI_FLAGS, val);
> > > -	}
> > > +	pci_imx_set_msi_en(pci);
> > >
> > >  	return 0;
> > >  }
> > > --
> > > 2.25.1
> >
>