linux-kernel - [PATCH 3.2 154/164] MIPS: Octeon: Remove udelay() causing huge IRQ latency

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Message-ID: <lsq.1438473758.722316683@decadent.org.uk>
Date:	Sun, 02 Aug 2015 01:02:38 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "David Daney" <ddaney@...ium.com>,
	"Jiri Kosina" <jkosina@...e.cz>,
	"Alexander Sverdlin" <alexander.sverdlin@...ia.com>,
	"Bjorn Helgaas" <bhelgaas@...gle.com>,
	"Mathias" <mathias.rulf@...ia.com>,
	"Randy Dunlap" <rdunlap@...radead.org>,
	"Masanari Iida" <standby24x7@...il.com>,
	"Rob Herring" <robh@...nel.org>, linux-mips@...ux-mips.org,
	"Ralf Baechle" <ralf@...ux-mips.org>
Subject: [PATCH 3.2 154/164] MIPS: Octeon: Remove udelay() causing huge
 IRQ latency

3.2.70-rc1 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>
---
 arch/mips/include/asm/octeon/pci-octeon.h | 3 ---
 arch/mips/pci/pci-octeon.c                | 6 ------
 arch/mips/pci/pcie-octeon.c               | 8 --------
 3 files changed, 17 deletions(-)

--- 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
-
 /*
  * The physical memory base mapped by BAR1.  256MB at the end of the
  * first 4GB.
--- a/arch/mips/pci/pci-octeon.c
+++ b/arch/mips/pci/pci-octeon.c
@@ -279,9 +279,6 @@ static int octeon_read_config(struct pci
 	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));
@@ -316,9 +313,6 @@ static int octeon_write_config(struct pc
 	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));
--- a/arch/mips/pci/pcie-octeon.c
+++ b/arch/mips/pci/pcie-octeon.c
@@ -1219,9 +1219,6 @@ static inline int octeon_pcie_write_conf
 					devfn & 0x7, reg, val);
 		return PCIBIOS_SUCCESSFUL;
 	}
-#if PCI_CONFIG_SPACE_DELAY
-	udelay(PCI_CONFIG_SPACE_DELAY);
-#endif
 	return PCIBIOS_FUNC_NOT_SUPPORTED;
 }
 

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