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From: Bjorn Helgaas <helgaas@kernel.org>
To: Toan Le <toan@os.amperecomputing.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Rob Herring <robh@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org, linux-pci@vger.kernel.org,
	Bjorn Helgaas <bhelgaas@google.com>
Subject: [PATCH] PCI: xgene: Fix CRS SV comment
Date: Tue, 26 Jan 2021 15:35:03 -0600	[thread overview]
Message-ID: <20210126213503.2922848-1-helgaas@kernel.org> (raw)

From: Bjorn Helgaas <bhelgaas@google.com>

Configuration Request Retry Status ("CRS") must be supported by all PCIe
devices.  CRS Software Visibility is an optional feature that enables a
Root Port to make CRS visible to software by returning a special data value
to complete a config read.

Clarify a comment to say that it is "CRS SV", not "CRS", that can be
enabled.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
---
 drivers/pci/controller/pci-xgene.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/controller/pci-xgene.c b/drivers/pci/controller/pci-xgene.c
index 85e7c98265e8..2afdc865253e 100644
--- a/drivers/pci/controller/pci-xgene.c
+++ b/drivers/pci/controller/pci-xgene.c
@@ -173,12 +173,13 @@ static int xgene_pcie_config_read32(struct pci_bus *bus, unsigned int devfn,
 
 	/*
 	 * The v1 controller has a bug in its Configuration Request
-	 * Retry Status (CRS) logic: when CRS is enabled and we read the
-	 * Vendor and Device ID of a non-existent device, the controller
-	 * fabricates return data of 0xFFFF0001 ("device exists but is not
-	 * ready") instead of 0xFFFFFFFF ("device does not exist").  This
-	 * causes the PCI core to retry the read until it times out.
-	 * Avoid this by not claiming to support CRS.
+	 * Retry Status (CRS) logic: when CRS Software Visibility is
+	 * enabled and we read the Vendor and Device ID of a non-existent
+	 * device, the controller fabricates return data of 0xFFFF0001
+	 * ("device exists but is not ready") instead of 0xFFFFFFFF
+	 * ("device does not exist").  This causes the PCI core to retry
+	 * the read until it times out.  Avoid this by not claiming to
+	 * support CRS SV.
 	 */
 	if (pci_is_root_bus(bus) && (port->version == XGENE_PCIE_IP_VER_1) &&
 	    ((where & ~0x3) == XGENE_V1_PCI_EXP_CAP + PCI_EXP_RTCTL))
-- 
2.25.1


WARNING: multiple messages have this Message-ID (diff)
From: Bjorn Helgaas <helgaas@kernel.org>
To: Toan Le <toan@os.amperecomputing.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Rob Herring <robh@kernel.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
	linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Subject: [PATCH] PCI: xgene: Fix CRS SV comment
Date: Tue, 26 Jan 2021 15:35:03 -0600	[thread overview]
Message-ID: <20210126213503.2922848-1-helgaas@kernel.org> (raw)

From: Bjorn Helgaas <bhelgaas@google.com>

Configuration Request Retry Status ("CRS") must be supported by all PCIe
devices.  CRS Software Visibility is an optional feature that enables a
Root Port to make CRS visible to software by returning a special data value
to complete a config read.

Clarify a comment to say that it is "CRS SV", not "CRS", that can be
enabled.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
---
 drivers/pci/controller/pci-xgene.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/controller/pci-xgene.c b/drivers/pci/controller/pci-xgene.c
index 85e7c98265e8..2afdc865253e 100644
--- a/drivers/pci/controller/pci-xgene.c
+++ b/drivers/pci/controller/pci-xgene.c
@@ -173,12 +173,13 @@ static int xgene_pcie_config_read32(struct pci_bus *bus, unsigned int devfn,
 
 	/*
 	 * The v1 controller has a bug in its Configuration Request
-	 * Retry Status (CRS) logic: when CRS is enabled and we read the
-	 * Vendor and Device ID of a non-existent device, the controller
-	 * fabricates return data of 0xFFFF0001 ("device exists but is not
-	 * ready") instead of 0xFFFFFFFF ("device does not exist").  This
-	 * causes the PCI core to retry the read until it times out.
-	 * Avoid this by not claiming to support CRS.
+	 * Retry Status (CRS) logic: when CRS Software Visibility is
+	 * enabled and we read the Vendor and Device ID of a non-existent
+	 * device, the controller fabricates return data of 0xFFFF0001
+	 * ("device exists but is not ready") instead of 0xFFFFFFFF
+	 * ("device does not exist").  This causes the PCI core to retry
+	 * the read until it times out.  Avoid this by not claiming to
+	 * support CRS SV.
 	 */
 	if (pci_is_root_bus(bus) && (port->version == XGENE_PCIE_IP_VER_1) &&
 	    ((where & ~0x3) == XGENE_V1_PCI_EXP_CAP + PCI_EXP_RTCTL))
-- 
2.25.1


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             reply	other threads:[~2021-01-26 23:49 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-26 21:35 Bjorn Helgaas [this message]
2021-01-26 21:35 ` [PATCH] PCI: xgene: Fix CRS SV comment Bjorn Helgaas
2021-01-28 10:47 ` Lorenzo Pieralisi
2021-01-28 10:47   ` Lorenzo Pieralisi

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