[PATCH 4.0 12/72] MIPS: Octeon: Remove udelay() causing huge IRQ latency

Greg Kroah-Hartman
2015-05-11T19:09:52Z

From: Alexander Sverdlin <alexander.sverdlin@nokia.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@nokia.com>
Cc: linux-mips@linux-mips.org
Cc: David Daney <ddaney@cavium.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Masanari Iida <standby24x7@gmail.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Mathias <mathias.rulf@nokia.com>
Patchwork: https://patchwork.linux-mips.org/patch/9576/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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
@@ -271,9 +271,6 @@ 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));
@@ -308,9 +305,6 @@ 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
@@ -1762,14 +1762,6 @@ static int octeon_pcie_write_config(unsi
default:
return PCIBIOS_FUNC_NOT_SUPPORTED;
}
-#if PCI_CONFIG_SPACE_DELAY
- /*
- * Delay on writes so that devices have time to come up. Some
- * bridges need this to allow time for the secondary busses to
- * work
- */
- udelay(PCI_CONFIG_SPACE_DELAY);
-#endif
return PCIBIOS_SUCCESSFUL;
}