PCI: Disable Relaxed Ordering for some Intel processors
According to the Intel spec section 3.9.1 said:
3.9.1 Optimizing PCIe Performance for Accesses Toward Coherent Memory
and Toward MMIO Regions (P2P)
In order to maximize performance for PCIe devices in the processors
listed in Table 3-6 below, the soft- ware should determine whether the
accesses are toward coherent memory (system memory) or toward MMIO
regions (P2P access to other devices). If the access is toward MMIO
region, then software can command HW to set the RO bit in the TLP
header, as this would allow hardware to achieve maximum throughput for
these types of accesses. For accesses toward coherent memory, software
can command HW to clear the RO bit in the TLP header (no RO), as this
would allow hardware to achieve maximum throughput for these types of
accesses.
Table 3-6. Intel Processor CPU RP Device IDs for Processors Optimizing
PCIe Performance
Processor CPU RP Device IDs
Intel Xeon processors based on 6F01H-6F0EH
Broadwell microarchitecture
Intel Xeon processors based on 2F01H-2F0EH
Haswell microarchitecture
It means some Intel processors has performance issue when use the Relaxed
Ordering Attribute, so disable Relaxed Ordering for these root port.
Signed-off-by: Casey Leedom <leedom at chelsio.com>
Signed-off-by: Ding Tianhong <dingtianhong at huawei.com>
Acked-by: Alexander Duyck <alexander.h.duyck at intel.com>
Acked-by: Ashok Raj <ashok.raj at intel.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
UnifiedSplitRaw
