The erratum and workaround are described by BCM5300X-ES300-RDS.pdf as below.
R10: PCIe Transactions Periodically Fail
Description: The BCM5300X PCIe does not maintain transaction ordering.
This may cause PCIe transaction failure.
Fix Comment: Add a dummy PCIe configuration read after a PCIe
configuration write to ensure PCIe configuration access
ordering. Set ES bit of CP0 configu7 register to enable
sync function so that the sync instruction is functional.
Resolution: hndpci.c: extpci_write_config()
hndmips.c: si_mips_init()
mipsinc.h CONF7_ES
This is fixed by the CFE MIPS bcmsi chipset driver also for BCM47XX.
Also the dummy PCIe configuration read is already implemented in the Linux
BCMA driver.
Enable ExternalSync in Config7 when CONFIG_BCMA_DRIVER_PCI_HOSTMODE=y
too so that the sync instruction is externalised.
Signed-off-by: Tokunori Ikegami <ikegami@xxxxxxxxxxxxxxxxxxxx>
Cc: Chris Packham <chris.packham@xxxxxxxxxxxxxxxxxxx>
Cc: Hauke Mehrtens <hauke@xxxxxxxxxx>
Cc: Rafał Miłecki <zajec5@xxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
---
Changes since v2:
- Move the change into platform-specific code bcm47xx_cpu_fixes() function from in generic code.
Changes since v1 resent:
- None.
Changes since v1 original:
- Change to use set_c0_config7 instead of write_c0_config7.
arch/mips/bcm47xx/setup.c | 7 +++++++
arch/mips/include/asm/mipsregs.h | 3 +++
2 files changed, 10 insertions(+)
diff --git a/arch/mips/bcm47xx/setup.c b/arch/mips/bcm47xx/setup.c
index 6054d49e608e..8fec219e1160 100644
--- a/arch/mips/bcm47xx/setup.c
+++ b/arch/mips/bcm47xx/setup.c
@@ -212,6 +212,13 @@ static int __init bcm47xx_cpu_fixes(void)
*/
if (bcm47xx_bus.bcma.bus.chipinfo.id == BCMA_CHIP_ID_BCM4706)
cpu_wait = NULL;
+
+ /*
+ * BCM47XX Erratum "R10: PCIe Transactions Periodically Fail"
+ * Enable ExternalSync for sync instruction to take effect
+ */
+ pr_info("ExternalSync has been enabled\n");
+ set_c0_config7(MIPS_CONF7_ES);
break;
#endif
}
diff --git a/arch/mips/include/asm/mipsregs.h b/arch/mips/include/asm/mipsregs.h
index 858752dac337..0f94acf60144 100644
--- a/arch/mips/include/asm/mipsregs.h
+++ b/arch/mips/include/asm/mipsregs.h
@@ -680,6 +680,8 @@
#define MIPS_CONF7_WII (_ULCAST_(1) << 31)
#define MIPS_CONF7_RPS (_ULCAST_(1) << 2)
+/* ExternalSync */
+#define MIPS_CONF7_ES (_ULCAST_(1) << 8)
#define MIPS_CONF7_IAR (_ULCAST_(1) << 10)
#define MIPS_CONF7_AR (_ULCAST_(1) << 16)
@@ -2759,6 +2761,7 @@ __BUILD_SET_C0(status)
__BUILD_SET_C0(cause)
__BUILD_SET_C0(config)
__BUILD_SET_C0(config5)
+__BUILD_SET_C0(config7)
__BUILD_SET_C0(intcontrol)
__BUILD_SET_C0(intctl)
__BUILD_SET_C0(srsmap)
--
2.16.1
