linux-kernel - Re: [v2] PCI: imx: make msi work without pcieportbus

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Message-ID: <1544692768.3137.25.camel@pengutronix.de>
Date:   Thu, 13 Dec 2018 10:19:28 +0100
From:   Lucas Stach <l.stach@...gutronix.de>
To:     Richard Zhu <hongxing.zhu@....com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "andrew.smirnov@...il.com" <andrew.smirnov@...il.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>
Subject: Re: [v2] PCI: imx: make msi work without pcieportbus

Hi Richard,

Am Donnerstag, den 13.12.2018, 08:02 +0000 schrieb Richard Zhu:
> MSI_EN of iMX PCIe RC would be asserted when
> PCIEPORTBUS driver is selected.
> Thus, the MSI works fine on iMX PCIe before.
> Assert it unconditionally when MSI is supported.
> Otherwise, the MSI wouldn't be triggered although
> the EP is present and the MSIs are assigned.

Thanks for digging into this issue. This seems like the right way
forward. However, did you test this with devices using legacy IRQs? 
I.e. booting with "nomsi" on the kernel command line to see if legacy
IRQs still work if this bit is set, or if we need to avoid setting this
when the user explicitly requests to disable MSIs?

Regards,
Lucas

> Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index 26087b3..d3e4296 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -74,6 +74,7 @@ struct imx6_pcie {
> >  #define PHY_PLL_LOCK_WAIT_USLEEP_MAX	200
>  
>  /* PCIe Root Complex registers (memory-mapped) */
> > +#define PCI_MSI_CAP				0x50
> >  #define PCIE_RC_LCR				0x7c
> >  #define PCIE_RC_LCR_MAX_LINK_SPEEDS_GEN1	0x1
> >  #define PCIE_RC_LCR_MAX_LINK_SPEEDS_GEN2	0x2
> @@ -926,6 +927,7 @@ 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)
> @@ -1070,6 +1072,11 @@ static int imx6_pcie_probe(struct platform_device *pdev)
> >  	ret = imx6_add_pcie_port(imx6_pcie, pdev);
> >  	if (ret < 0)
> >  		return ret;
> > +	if (IS_ENABLED(CONFIG_PCI_MSI)) {
> > +		val = dw_pcie_readw_dbi(pci, PCI_MSI_CAP + PCI_MSI_FLAGS);
> > +		val |= PCI_MSI_FLAGS_ENABLE;
> > +		dw_pcie_writew_dbi(pci, PCI_MSI_CAP + PCI_MSI_FLAGS, val);
> > +	}
>  
> >  	return 0;
>  }