linux-kernel - [PATCH] PCI: dw-rockchip: Configure max payload size on host init

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Message-Id: <20250416151926.140202-1-18255117159@163.com>
Date: Wed, 16 Apr 2025 23:19:26 +0800
From: Hans Zhang <18255117159@....com>
To: lpieralisi@...nel.org,
	kw@...ux.com,
	bhelgaas@...gle.com,
	heiko@...ech.de
Cc: manivannan.sadhasivam@...aro.org,
	robh@...nel.org,
	jingoohan1@...il.com,
	thomas.richard@...tlin.com,
	linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-rockchip@...ts.infradead.org,
	Hans Zhang <18255117159@....com>
Subject: [PATCH] PCI: dw-rockchip: Configure max payload size on host init

The RK3588's PCIe controller defaults to a 128-byte max payload size,
but its hardware capability actually supports 256 bytes. This results
in suboptimal performance with devices that support larger payloads.

Signed-off-by: Hans Zhang <18255117159@....com>
---
 drivers/pci/controller/dwc/pcie-dw-rockchip.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-dw-rockchip.c b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
index c624b7ebd118..5bbb536a2576 100644
--- a/drivers/pci/controller/dwc/pcie-dw-rockchip.c
+++ b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
@@ -477,6 +477,22 @@ static irqreturn_t rockchip_pcie_ep_sys_irq_thread(int irq, void *arg)
 	return IRQ_HANDLED;
 }
 
+static void rockchip_pcie_set_max_payload(struct rockchip_pcie *rockchip)
+{
+	struct dw_pcie *pci = &rockchip->pci;
+	u32 dev_cap, dev_ctrl;
+	u16 offset;
+
+	offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
+	dev_cap = dw_pcie_readl_dbi(pci, offset + PCI_EXP_DEVCAP);
+	dev_cap &= PCI_EXP_DEVCAP_PAYLOAD;
+
+	dev_ctrl = dw_pcie_readl_dbi(pci, offset + PCI_EXP_DEVCTL);
+	dev_ctrl &= ~PCI_EXP_DEVCTL_PAYLOAD;
+	dev_ctrl |= dev_cap << 5;
+	dw_pcie_writel_dbi(pci, offset + PCI_EXP_DEVCTL, dev_ctrl);
+}
+
 static int rockchip_pcie_configure_rc(struct platform_device *pdev,
 				      struct rockchip_pcie *rockchip)
 {
@@ -511,6 +527,8 @@ static int rockchip_pcie_configure_rc(struct platform_device *pdev,
 	pp->ops = &rockchip_pcie_host_ops;
 	pp->use_linkup_irq = true;
 
+	rockchip_pcie_set_max_payload(rockchip);
+
 	ret = dw_pcie_host_init(pp);
 	if (ret) {
 		dev_err(dev, "failed to initialize host\n");

base-commit: a24588245776dafc227243a01bfbeb8a59bafba9
-- 
2.25.1