Re: [v6] PCI: imx: make msi work without CONFIG_PCIEPORTBUS=y

[Bjorn Helgaas <helgaas@kernel.org>]

On Fri, Dec 21, 2018 at 04:33:38AM +0000, Richard Zhu wrote:
> The MSI Enable bit in the MSI Capability (PCIe r4.0, sec 7.7.1.2)
> controls whether a Function can request service using MSI.
> 
> i.MX6 Root Ports implement the MSI Capability and may use MSI to
> request service for events like PME, hotplug, AER, etc.  In
> addition, on i.MX6, the MSI Enable bit controls delivery of MSI
> interrupts from components below the Root Port.
> 
> Prior to commit f3fdfc4ac3a2 ("PCI: Remove host driver Kconfig selection
> of CONFIG_PCIEPORTBUS"), enabling CONFIG_PCI_IMX6 automatically also
> enabled CONFIG_PCIEPORTBUS, and when portdrv claimed the Root Ports,
> it set the MSI Enable bit so it could use PME, hotplug, AER, etc.
> As a side effect, that also enabled delivery of MSI interrupts from
> downstream components.
> 
> After f3fdfc4ac3a2, the imx6q-pcie driver can operate without
> portdrv, but that means imx6q-pcie must set the MSI Enable bit
> itself if downstream components use MSI.
> 
> Fixes: f3fdfc4ac3a2 ("PCI: Remove host driver Kconfig selection of CONFIG_PCIEPORTBUS")
> 
> Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
> Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
> Tested-by: Sven Van Asbroeck <TheSven73@googlemail.com>
> Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

Applied with Trent's tested-by to pci/imx6 for v4.21.

> ---
> Changes v1 -> v2:
> * Assert the MSI_EN unconditionally when MSI is supported.
> Changes v2 -> v3:
> * Remove the IS_ENABLED(CONFIG_PCI_MSI) since the driver depends on
> PCI_MSI_IRQ_DOMAIN
> * Extended with a check for pci_msi_enabled() to see if the user
> explicitly want legacy IRQs
> Changes v3 -> v4:
> * Refer to Bjorn's comments, refine the subject and commit log and change
> the PCI_MSI_CAP to PCIE_RC_IMX6_MSI_CAP.
> Changes v4 -> v5:
> * Correct one spell mistake from PCIE_RC_MSI_IMX6_CAP to
> PCIE_RC_IMX6_MSI_CAP.
> Changes v5 -> v6:
> * Update with Bjorn's commit.
> * One "commit" added in "Prior to f3fdfc4ac3a2" refer to the complain of
> checkpatch.pl.
> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index e563ca9..73542dd 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -82,6 +82,7 @@ struct imx6_pcie {
>  #define PHY_PLL_LOCK_WAIT_USLEEP_MAX	200
>  
>  /* PCIe Root Complex registers (memory-mapped) */
> +#define PCIE_RC_IMX6_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
> @@ -999,6 +1000,7 @@ 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)
> @@ -1149,6 +1151,14 @@ static int imx6_pcie_probe(struct platform_device *pdev)
>  	if (ret < 0)
>  		return ret;
>  
> +	if (pci_msi_enabled()) {
> +		val = dw_pcie_readw_dbi(pci, PCIE_RC_IMX6_MSI_CAP +
> +				PCI_MSI_FLAGS);
> +		val |= PCI_MSI_FLAGS_ENABLE;
> +		dw_pcie_writew_dbi(pci, PCIE_RC_IMX6_MSI_CAP +
> +				PCI_MSI_FLAGS, val);
> +	}
> +
>  	return 0;
>  }
>  
> -- 
> 2.7.4
> 
> 
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