linux-kernel - [PATCH 2.6.32 33/62] MIPS: Octeon: Remove udelay() causing huge IRQ latency

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Date:	Sun, 13 Sep 2015 00:56:39 +0200
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Alexander Sverdlin <alexander.sverdlin@...ia.com>,
	linux-mips@...ux-mips.org, David Daney <ddaney@...ium.com>,
	Rob Herring <robh@...nel.org>, Jiri Kosina <jkosina@...e.cz>,
	Randy Dunlap <rdunlap@...radead.org>,
	Masanari Iida <standby24x7@...il.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Mathias <mathias.rulf@...ia.com>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Ben Hutchings <ben@...adent.org.uk>, Willy Tarreau <w@....eu>
Subject: [PATCH 2.6.32 33/62] MIPS: Octeon: Remove udelay() causing huge IRQ latency

2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------

From: Alexander Sverdlin <alexander.sverdlin@...ia.com>

commit 73bf3c2a500b2db8ac966469591196bf55afb409 upstream.

udelay() in PCI/PCIe read/write callbacks cause 30ms IRQ latency on Octeon
platforms because these operations are called from PCI_OP_READ() and
PCI_OP_WRITE() under raw_spin_lock_irqsave().

Signed-off-by: Alexander Sverdlin <alexander.sverdlin@...ia.com>
Cc: linux-mips@...ux-mips.org
Cc: David Daney <ddaney@...ium.com>
Cc: Rob Herring <robh@...nel.org>
Cc: Jiri Kosina <jkosina@...e.cz>
Cc: Randy Dunlap <rdunlap@...radead.org>
Cc: Masanari Iida <standby24x7@...il.com>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Mathias <mathias.rulf@...ia.com>
Patchwork: https://patchwork.linux-mips.org/patch/9576/
Signed-off-by: Ralf Baechle <ralf@...ux-mips.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
(cherry picked from commit 53493d44a771a3155ee12b6ac668fb2543d21a7a)

Signed-off-by: Willy Tarreau <w@....eu>
---
 arch/mips/include/asm/octeon/pci-octeon.h | 3 ---
 arch/mips/pci/pci-octeon.c                | 6 ------
 arch/mips/pci/pcie-octeon.c               | 3 ---
 3 files changed, 12 deletions(-)

diff --git a/arch/mips/include/asm/octeon/pci-octeon.h b/arch/mips/include/asm/octeon/pci-octeon.h
index 6ac5d3e..5eda9f0 100644
--- a/arch/mips/include/asm/octeon/pci-octeon.h
+++ b/arch/mips/include/asm/octeon/pci-octeon.h
@@ -11,9 +11,6 @@
 
 #include <linux/pci.h>
 
-/* Some PCI cards require delays when accessing config space. */
-#define PCI_CONFIG_SPACE_DELAY 10000
-
 /*
  * pcibios_map_irq() is defined inside pci-octeon.c. All it does is
  * call the Octeon specific version pointed to by this variable. This
diff --git a/arch/mips/pci/pci-octeon.c b/arch/mips/pci/pci-octeon.c
index 9cb0c80..dae7ff7 100644
--- a/arch/mips/pci/pci-octeon.c
+++ b/arch/mips/pci/pci-octeon.c
@@ -274,9 +274,6 @@ static int octeon_read_config(struct pci_bus *bus, unsigned int devfn,
 	pci_addr.s.func = devfn & 0x7;
 	pci_addr.s.reg = reg;
 
-#if PCI_CONFIG_SPACE_DELAY
-	udelay(PCI_CONFIG_SPACE_DELAY);
-#endif
 	switch (size) {
 	case 4:
 		*val = le32_to_cpu(cvmx_read64_uint32(pci_addr.u64));
@@ -311,9 +308,6 @@ static int octeon_write_config(struct pci_bus *bus, unsigned int devfn,
 	pci_addr.s.func = devfn & 0x7;
 	pci_addr.s.reg = reg;
 
-#if PCI_CONFIG_SPACE_DELAY
-	udelay(PCI_CONFIG_SPACE_DELAY);
-#endif
 	switch (size) {
 	case 4:
 		cvmx_write64_uint32(pci_addr.u64, cpu_to_le32(val));
diff --git a/arch/mips/pci/pcie-octeon.c b/arch/mips/pci/pcie-octeon.c
index 6aa5c54..97813f3 100644
--- a/arch/mips/pci/pcie-octeon.c
+++ b/arch/mips/pci/pcie-octeon.c
@@ -1192,9 +1192,6 @@ static inline int octeon_pcie_write_config(int pcie_port, struct pci_bus *bus,
 					devfn & 0x7, reg, val);
 		return PCIBIOS_SUCCESSFUL;
 	}
-#if PCI_CONFIG_SPACE_DELAY
-	udelay(PCI_CONFIG_SPACE_DELAY);
-#endif
 	return PCIBIOS_FUNC_NOT_SUPPORTED;
 }
 
-- 
1.7.12.2.21.g234cd45.dirty



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