linux-kernel - [PATCH 1/2] PCI: brcmstb: Add a way to indicate if PCIe bridge is active

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Message-Id: <20250613220843.698227-2-james.quinlan@broadcom.com>
Date: Fri, 13 Jun 2025 18:08:42 -0400
From: Jim Quinlan <james.quinlan@...adcom.com>
To: linux-pci@...r.kernel.org,
	Nicolas Saenz Julienne <nsaenz@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Cyril Brulebois <kibi@...ian.org>,
	bcm-kernel-feedback-list@...adcom.com,
	jim2101024@...il.com,
	james.quinlan@...adcom.com
Cc: Florian Fainelli <florian.fainelli@...adcom.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kwilczynski@...nel.org>,
	Manivannan Sadhasivam <mani@...nel.org>,
	Rob Herring <robh@...nel.org>,
	linux-rpi-kernel@...ts.infradead.org (moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE),
	linux-arm-kernel@...ts.infradead.org (moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE),
	linux-kernel@...r.kernel.org (open list)
Subject: [PATCH 1/2] PCI: brcmstb: Add a way to indicate if PCIe bridge is active

In a future commit, a new handler will be introduced that in part does
reads and writes to some of the PCIe registers.  When this handler is
invoked, it is paramount that it does not do these register accesses when
the PCIe bridge is inactive, as this will cause CPU abort errors.

To solve this we keep a spinlock that guards a variable which indicates
whether the bridge is on or off.  When the bridge is on, access of the PCIe
HW registers may proceed.

Since there are multiple ways to reset the bridge, we introduce a general
function to obtain the spinlock, call the specific function that is used
for the specific SoC, sets the bridge active indicator variable, and
releases the spinlock.

Signed-off-by: Jim Quinlan <james.quinlan@...adcom.com>
---
 drivers/pci/controller/pcie-brcmstb.c | 40 +++++++++++++++++++++++----
 1 file changed, 35 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
index 92887b394eb4..400854c893d8 100644
--- a/drivers/pci/controller/pcie-brcmstb.c
+++ b/drivers/pci/controller/pcie-brcmstb.c
@@ -29,6 +29,7 @@
 #include <linux/reset.h>
 #include <linux/sizes.h>
 #include <linux/slab.h>
+#include <linux/spinlock.h>
 #include <linux/string.h>
 #include <linux/types.h>
 
@@ -254,6 +255,7 @@ struct pcie_cfg_data {
 	int (*perst_set)(struct brcm_pcie *pcie, u32 val);
 	int (*bridge_sw_init_set)(struct brcm_pcie *pcie, u32 val);
 	int (*post_setup)(struct brcm_pcie *pcie);
+	bool has_err_report;
 };
 
 struct subdev_regulators {
@@ -299,6 +301,8 @@ struct brcm_pcie {
 	struct subdev_regulators *sr;
 	bool			ep_wakeup_capable;
 	const struct pcie_cfg_data	*cfg;
+	bool			bridge_on;
+	spinlock_t		bridge_lock;
 };
 
 static inline bool is_bmips(const struct brcm_pcie *pcie)
@@ -306,6 +310,24 @@ static inline bool is_bmips(const struct brcm_pcie *pcie)
 	return pcie->cfg->soc_base == BCM7435 || pcie->cfg->soc_base == BCM7425;
 }
 
+static inline int brcm_pcie_bridge_sw_init_set(struct brcm_pcie *pcie, u32 val)
+{
+	unsigned long flags;
+	int ret;
+
+	if (pcie->cfg->has_err_report)
+		spin_lock_irqsave(&pcie->bridge_lock, flags);
+
+	ret = pcie->cfg->bridge_sw_init_set(pcie, val);
+	if (ret)
+		pcie->bridge_on = !val;
+
+	if (pcie->cfg->has_err_report)
+		spin_unlock_irqrestore(&pcie->bridge_lock, flags);
+
+	return ret;
+}
+
 /*
  * This is to convert the size of the inbound "BAR" region to the
  * non-linear values of PCIE_X_MISC_RC_BAR[123]_CONFIG_LO.SIZE
@@ -1078,7 +1100,7 @@ static int brcm_pcie_setup(struct brcm_pcie *pcie)
 	int memc, ret;
 
 	/* Reset the bridge */
-	ret = pcie->cfg->bridge_sw_init_set(pcie, 1);
+	ret = brcm_pcie_bridge_sw_init_set(pcie, 1);
 	if (ret)
 		return ret;
 
@@ -1094,7 +1116,7 @@ static int brcm_pcie_setup(struct brcm_pcie *pcie)
 	usleep_range(100, 200);
 
 	/* Take the bridge out of reset */
-	ret = pcie->cfg->bridge_sw_init_set(pcie, 0);
+	ret = brcm_pcie_bridge_sw_init_set(pcie, 0);
 	if (ret)
 		return ret;
 
@@ -1545,7 +1567,7 @@ static int brcm_pcie_turn_off(struct brcm_pcie *pcie)
 
 	if (!(pcie->cfg->quirks & CFG_QUIRK_AVOID_BRIDGE_SHUTDOWN))
 		/* Shutdown PCIe bridge */
-		ret = pcie->cfg->bridge_sw_init_set(pcie, 1);
+		ret = brcm_pcie_bridge_sw_init_set(pcie, 1);
 
 	return ret;
 }
@@ -1633,7 +1655,9 @@ static int brcm_pcie_resume_noirq(struct device *dev)
 		goto err_reset;
 
 	/* Take bridge out of reset so we can access the SERDES reg */
-	pcie->cfg->bridge_sw_init_set(pcie, 0);
+	ret = brcm_pcie_bridge_sw_init_set(pcie, 0);
+	if (ret)
+		goto err_reset;
 
 	/* SERDES_IDDQ = 0 */
 	tmp = readl(base + HARD_DEBUG(pcie));
@@ -1901,7 +1925,10 @@ static int brcm_pcie_probe(struct platform_device *pdev)
 	if (ret)
 		return dev_err_probe(&pdev->dev, ret, "could not enable clock\n");
 
-	pcie->cfg->bridge_sw_init_set(pcie, 0);
+	ret = brcm_pcie_bridge_sw_init_set(pcie, 0);
+	if (ret)
+		return dev_err_probe(&pdev->dev, ret,
+				     "could not un-reset the bridge\n");
 
 	if (pcie->swinit_reset) {
 		ret = reset_control_assert(pcie->swinit_reset);
@@ -1976,6 +2003,9 @@ static int brcm_pcie_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	if (pcie->cfg->has_err_report)
+		spin_lock_init(&pcie->bridge_lock);
+
 	return 0;
 
 fail:
-- 
2.34.1