[PATCH v6 3/5] PCI: brcmstb: Set higher value for internal bus timeout

From: Jim Quinlan <james.quinlan@broadcom.com>
To: linux-pci@vger.kernel.org,
	Nicolas Saenz Julienne <nsaenz@kernel.org>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Cyril Brulebois <kibi@debian.org>,
	Phil Elwell <phil@raspberrypi.com>,
	bcm-kernel-feedback-list@broadcom.com,
	james.quinlan@broadcom.com
Cc: "Florian Fainelli" <f.fainelli@gmail.com>,
	"Jim Quinlan" <jim2101024@gmail.com>,
	"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
	"Krzysztof Wilczyński" <kw@linux.com>,
	"Rob Herring" <robh@kernel.org>,
	linux-rpi-kernel@lists.infradead.org (moderated list:BROADCOM
	BCM2711/BCM2835 ARM ARCHITECTURE),
	linux-arm-kernel@lists.infradead.org (moderated list:BROADCOM
	BCM2711/BCM2835 ARM ARCHITECTURE),
	linux-kernel@vger.kernel.org (open list)
Subject: [PATCH v6 3/5] PCI: brcmstb: Set higher value for internal bus timeout
Date: Fri, 23 Jun 2023 10:40:56 -0400	[thread overview]
Message-ID: <20230623144100.34196-4-james.quinlan@broadcom.com> (raw)
In-Reply-To: <20230623144100.34196-1-james.quinlan@broadcom.com>


[-- Attachment #1.1: Type: text/plain, Size: 1928 bytes --]

During long periods of the PCIe RC HW being in an L1SS sleep state, there
may be a timeout on an internal bus access, even though there may not be
any PCIe access involved.  Such a timeout will cause a subsequent CPU
abort.

So, when "brcm,enable-l1ss" is observed, we increase the timeout value to
four seconds instead of using its HW default.

Signed-off-by: Jim Quinlan <james.quinlan@broadcom.com>
Tested-by: Florian Fainelli <f.fainelli@gmail.com>
---
 drivers/pci/controller/pcie-brcmstb.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
index d30636a725d7..fe0415a98c63 100644
--- a/drivers/pci/controller/pcie-brcmstb.c
+++ b/drivers/pci/controller/pcie-brcmstb.c
@@ -1034,6 +1034,21 @@ static int brcm_pcie_setup(struct brcm_pcie *pcie)
 	return 0;
 }
 
+/*
+ * This extends the timeout period for an access to an internal bus.  This
+ * access timeout may occur during L1SS sleep periods even without the
+ * presence of a PCIe access.
+ */
+static void brcm_extend_rbus_timeout(struct brcm_pcie *pcie)
+{
+	/* TIMEOUT register is two registers before RGR1_SW_INIT_1 */
+	const unsigned int REG_OFFSET = PCIE_RGR1_SW_INIT_1(pcie) - 8;
+	u32 timeout_us = 4000000; /* 4 seconds, our setting for L1SS */
+
+	/* Each unit in timeout register is 1/216,000,000 seconds */
+	writel(216 * timeout_us, pcie->base + REG_OFFSET);
+}
+
 static void brcm_config_clkreq(struct brcm_pcie *pcie)
 {
 	bool l1ss = of_property_read_bool(pcie->np, "brcm,enable-l1ss");
@@ -1059,6 +1074,7 @@ static void brcm_config_clkreq(struct brcm_pcie *pcie)
 		 * of 400ns, as specified in 3.2.5.2.2 of the PCI Express
 		 * Mini CEM 2.0 specification.
 		 */
+		brcm_extend_rbus_timeout(pcie);
 		clkreq_set |= PCIE_MISC_HARD_PCIE_HARD_DEBUG_L1SS_ENABLE_MASK;
 		dev_info(pcie->dev, "bi-dir CLKREQ# for L1SS power savings");
 	} else {
-- 
2.17.1


[-- Attachment #1.2: S/MIME Cryptographic Signature --]
[-- Type: application/pkcs7-signature, Size: 4210 bytes --]

[-- Attachment #2: Type: text/plain, Size: 176 bytes --]

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
