From 96ebf0a9fc30646420af7ef5c273b81d35a78a75 Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.com>
Date: Wed, 1 Nov 2023 10:13:29 +0000
Subject: [PATCH 0695/1085] PCI: brcmstb: Change RCB_{MPS,64B}_MODE bits

Upstream commit [1] unconditionally sets the RCB_MPS and RCB_64B bits
that govern where packets are split. We think this is potentially
harmful, particularly on CM4 and Pi 5 where potentially any PCIe devices
could be attached.

Make RCB_MPS conditional on a DT property and never set RCB_64B.

[1] commit 602fb860945f ("PCI: brcmstb: Set RCB_{MPS,64B}_MODE bits")

Signed-off-by: Phil Elwell <phil@raspberrypi.com>
---
 drivers/pci/controller/pcie-brcmstb.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/drivers/pci/controller/pcie-brcmstb.c
+++ b/drivers/pci/controller/pcie-brcmstb.c
@@ -336,6 +336,7 @@ struct brcm_pcie {
 	struct device_node	*np;
 	bool			ssc;
 	bool			l1ss;
+	bool			rcb_mps_mode;
 	int			gen;
 	u64			msi_target_addr;
 	struct brcm_msi		*msi;
@@ -1196,14 +1197,14 @@ static int brcm_pcie_setup(struct brcm_p
 
 	/*
 	 * Set SCB_MAX_BURST_SIZE, CFG_READ_UR_MODE, SCB_ACCESS_EN,
-	 * RCB_MPS_MODE, RCB_64B_MODE
+	 * RCB_MPS_MODE
 	 */
 	tmp = readl(base + PCIE_MISC_MISC_CTRL);
 	u32p_replace_bits(&tmp, 1, PCIE_MISC_MISC_CTRL_SCB_ACCESS_EN_MASK);
 	u32p_replace_bits(&tmp, 1, PCIE_MISC_MISC_CTRL_CFG_READ_UR_MODE_MASK);
 	u32p_replace_bits(&tmp, burst, PCIE_MISC_MISC_CTRL_MAX_BURST_SIZE_MASK);
-	u32p_replace_bits(&tmp, 1, PCIE_MISC_MISC_CTRL_PCIE_RCB_MPS_MODE_MASK);
-	u32p_replace_bits(&tmp, 1, PCIE_MISC_MISC_CTRL_PCIE_RCB_64B_MODE_MASK);
+	if (pcie->rcb_mps_mode)
+		u32p_replace_bits(&tmp, 1, PCIE_MISC_MISC_CTRL_PCIE_RCB_MPS_MODE_MASK);
 	writel(tmp, base + PCIE_MISC_MISC_CTRL);
 
 	brcm_pcie_set_tc_qos(pcie);
@@ -1917,6 +1918,7 @@ static int brcm_pcie_probe(struct platfo
 
 	pcie->ssc = of_property_read_bool(np, "brcm,enable-ssc");
 	pcie->l1ss = of_property_read_bool(np, "brcm,enable-l1ss");
+	pcie->rcb_mps_mode = of_property_read_bool(np, "brcm,enable-mps-rcb");
 
 	ret = clk_prepare_enable(pcie->clk);
 	if (ret) {