linux-kernel - [PATCH] ACPI: pci_root: Clear the acpi dependencies after PCI root bridge initialization on RISC-V

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Message-ID: <20251203140716.3065-1-huyuye812@163.com>
Date: Wed,  3 Dec 2025 22:07:15 +0800
From: huyuye <huyuye812@....com>
To: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: "Rafael J . Wysocki" <rafael@...nel.org>,
	Len Brown <lenb@...nel.org>,
	linux-pci@...r.kernel.org,
	linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	dai.hualiang@....com.cn,
	deng.weixian@....com.cn,
	guo.chang2@....com.cn,
	liu.qingtao2@....com.cn,
	wu.jiabao@....com.cn,
	lin.yongchun@....com.cn,
	hu.yuye@....com.cn,
	zhang.longxiang@....com.cn,
	zuo.jiang@....com.cn,
	li.kunpeng@....com.cn,
	huyuye <huyuye812@....com>
Subject: [PATCH] ACPI: pci_root: Clear the acpi dependencies after PCI root bridge initialization on RISC-V

On RISC-V platforms with multiple PCI root bridges, the enumeration
order varies randomly across reboots due to APLIC driver initialization
occurring after ACPI device scanning. This defers PCI probing to a
unbound workqueue, resulting in non-deterministic device discovery
sequences.

Such random enumeration leads to changes in device naming across each
boot, which disrupts storage configurations, network settings, and
severely impacts the stability of server maintenance.

By adding the acpi_dev_clear_dependencies() call in acpi_pci_root_add(),
this patch enables the firmware to actively control the enumeration order
of multiple PCI root bridges through the ACPI _DEP method, providing the
firmware with the opportunity to initialize devices in the intended order,
thereby ensuring consistent enumeration results across multiple boots.

Signed-off-by: huyuye <huyuye812@....com>
---
 drivers/acpi/pci_root.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 74ade4160314..f5b5aa7d5f93 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -760,6 +760,20 @@ static int acpi_pci_root_add(struct acpi_device *device,
 	pci_lock_rescan_remove();
 	pci_bus_add_devices(root->bus);
 	pci_unlock_rescan_remove();
+#ifdef CONFIG_RISCV
+    /*
+     * Clear dependencies to allow dependent devices to be enumerated.
+     * This is particularly important for RISC-V platforms where multiple
+     * PCIe host bridges may have initialization order dependencies defined
+     * via ACPI _DEP method in DSDT. If a host bridge B depends on host
+     * bridge A (via _DEP), this call allows bridge B to proceed with
+     * enumeration after bridge A is fully initialized.
+     */
+#ifdef CONFIG_ACPI
+	if (!acpi_disabled)
+		acpi_dev_clear_dependencies(device);
+#endif
+#endif
 	return 1;

 remove_dmar:
-- 
2.43.0