linux-kernel - [PATCH v2 -next 05/11] PCI: brcmstb: Restore CRS in RootCtl after prstn

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Message-ID: <20240910151845.17308-6-svarbanov@suse.de>
Date: Tue, 10 Sep 2024 18:18:39 +0300
From: Stanimir Varbanov <svarbanov@...e.de>
To: 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>,
	Stanimir Varbanov <svarbanov@...e.de>
Subject: [PATCH v2 -next 05/11] PCI: brcmstb: Restore CRS in RootCtl after prstn_n

RootCtl bits might reset by perst_n during probe, re-enable
CRS SVE here in pcie_start_link.

Signed-off-by: Stanimir Varbanov <svarbanov@...e.de>
---
 drivers/pci/controller/pcie-brcmstb.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
index 7bd85566c242..f2a7a8e93a74 100644
--- a/drivers/pci/controller/pcie-brcmstb.c
+++ b/drivers/pci/controller/pcie-brcmstb.c
@@ -1271,7 +1271,7 @@ static int brcm_pcie_start_link(struct brcm_pcie *pcie)
 {
 	struct device *dev = pcie->dev;
 	void __iomem *base = pcie->base;
-	u16 nlw, cls, lnksta;
+	u16 nlw, cls, lnksta, tmp16;
 	bool ssc_good = false;
 	int ret, i;
 
@@ -1319,6 +1319,17 @@ static int brcm_pcie_start_link(struct brcm_pcie *pcie)
 		 pci_speed_string(pcie_link_speed[cls]), nlw,
 		 ssc_good ? "(SSC)" : "(!SSC)");
 
+	/*
+	 * RootCtl bits are reset by perst_n, which undoes pci_enable_crs()
+	 * called prior to pci_add_new_bus() during probe. Re-enable here.
+	 */
+	tmp16 = readw(base + BRCM_PCIE_CAP_REGS + PCI_EXP_RTCAP);
+	if (tmp16 & PCI_EXP_RTCAP_CRSVIS) {
+		tmp16 = readw(base + BRCM_PCIE_CAP_REGS + PCI_EXP_RTCTL);
+		u16p_replace_bits(&tmp16, 1, PCI_EXP_RTCTL_CRSSVE);
+		writew(tmp16, base + BRCM_PCIE_CAP_REGS + PCI_EXP_RTCTL);
+	}
+
 	return 0;
 }
 
-- 
2.35.3