linux-kernel - Re: [PATCH v4 06/10] PCI: brcmstb: Enable external MSI-X if available

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Message-ID: <f0a734d9-6bf6-4d28-b30b-99b6be9f62dc@broadcom.com>
Date: Wed, 11 Dec 2024 15:01:40 -0500
From: James Quinlan <james.quinlan@...adcom.com>
To: Stanimir Varbanov <svarbanov@...e.de>, linux-kernel@...r.kernel.org,
 devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-rpi-kernel@...ts.infradead.org, linux-pci@...r.kernel.org,
 Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Florian Fainelli <florian.fainelli@...adcom.com>,
 Jim Quinlan <jim2101024@...il.com>,
 Nicolas Saenz Julienne <nsaenz@...nel.org>,
 Bjorn Helgaas <bhelgaas@...gle.com>,
 Lorenzo Pieralisi <lpieralisi@...nel.org>, kw@...ux.com,
 Philipp Zabel <p.zabel@...gutronix.de>,
 Andrea della Porta <andrea.porta@...e.com>,
 Phil Elwell <phil@...pberrypi.com>, Jonathan Bell <jonathan@...pberrypi.com>
Subject: Re: [PATCH v4 06/10] PCI: brcmstb: Enable external MSI-X if available

On 10/25/24 08:45, Stanimir Varbanov wrote:
> On RPi5 there is an external MIP MSI-X interrupt controller
> which can handle up to 64 interrupts.
>
> Signed-off-by: Stanimir Varbanov <svarbanov@...e.de>
> ---
> v3 -> v4:
>   - no changes.
>
>   drivers/pci/controller/pcie-brcmstb.c | 63 +++++++++++++++++++++++++--
>   1 file changed, 59 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
> index c01462b07eea..af01a7915c94 100644
> --- a/drivers/pci/controller/pcie-brcmstb.c
> +++ b/drivers/pci/controller/pcie-brcmstb.c
> @@ -1318,6 +1318,52 @@ static int brcm_pcie_start_link(struct brcm_pcie *pcie)
>   	return 0;
>   }
>   
> +static int brcm_pcie_enable_external_msix(struct brcm_pcie *pcie,
> +					  struct device_node *msi_np)
> +{
> +	struct inbound_win inbound_wins[PCIE_BRCM_MAX_INBOUND_WINS];
> +	u64 msi_pci_addr, msi_phys_addr;
> +	struct resource r;
> +	int mip_bar, ret;
> +	u32 val, reg;
> +
> +	ret = of_property_read_reg(msi_np, 1, &msi_pci_addr, NULL);
> +	if (ret)
> +		return ret;
> +
> +	ret = of_address_to_resource(msi_np, 0, &r);
> +	if (ret)
> +		return ret;
> +
> +	msi_phys_addr = r.start;
> +
> +	/* Find free inbound window for MIP access */
> +	mip_bar = brcm_pcie_get_inbound_wins(pcie, inbound_wins);
> +	if (mip_bar < 0)
> +		return mip_bar;
> +
> +	mip_bar += 1;
> +	reg = brcm_bar_reg_offset(mip_bar);
> +
> +	val = lower_32_bits(msi_pci_addr);
> +	val |= brcm_pcie_encode_ibar_size(SZ_4K);
> +	writel(val, pcie->base + reg);
> +
> +	val = upper_32_bits(msi_pci_addr);
> +	writel(val, pcie->base + reg + 4);
> +
> +	reg = brcm_ubus_reg_offset(mip_bar);
> +
> +	val = lower_32_bits(msi_phys_addr);
> +	val |= PCIE_MISC_UBUS_BAR1_CONFIG_REMAP_ACCESS_EN_MASK;
> +	writel(val, pcie->base + reg);
> +
> +	val = upper_32_bits(msi_phys_addr);
> +	writel(val, pcie->base + reg + 4);

Hi Stan,

It looks like all this is doing is setting up an identity-mapped inbound 
window, is that correct?  If so, couldn't you get the same effect by 
adding an identity-mapped dma-range in the PCIe DT node?

Jim Quinlan  Broadcom STB/CM

> +
> +	return 0;
> +}
> +
>   static const char * const supplies[] = {
>   	"vpcie3v3",
>   	"vpcie3v3aux",
> @@ -1879,11 +1925,20 @@ static int brcm_pcie_probe(struct platform_device *pdev)
>   		goto fail;
>   	}
>   
> -	msi_np = of_parse_phandle(pcie->np, "msi-parent", 0);
> -	if (pci_msi_enabled() && msi_np == pcie->np) {
> -		ret = brcm_pcie_enable_msi(pcie);
> +	if (pci_msi_enabled()) {
> +		msi_np = of_parse_phandle(pcie->np, "msi-parent", 0);
> +		const char *str;
> +
> +		if (msi_np == pcie->np) {
> +			str = "internal MSI";
> +			ret = brcm_pcie_enable_msi(pcie);
> +		} else {
> +			str = "external MSI-X";
> +			ret = brcm_pcie_enable_external_msix(pcie, msi_np);
> +		}
> +
>   		if (ret) {
> -			dev_err(pcie->dev, "probe of internal MSI failed");
> +			dev_err(pcie->dev, "enable of %s failed\n", str);
>   			goto fail;
>   		}
>   	}