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[6/7] xen/arm: rcar4: add simple optimization to avoid ATU reprogramming

Message ID 499ef211f469949e5fefd47b17e135b26325e0e5.1740382735.git.mykyta_poturai@epam.com (mailing list archive)
State New
Headers show
Series Add support for R-Car Gen4 PCI host controller | expand

Commit Message

Mykyta Poturai Feb. 24, 2025, 9:18 a.m. UTC 
From: Volodymyr Babchuk <volodymyr_babchuk@epam.com>

There are high chances that there will be a number of a consecutive
accesses to configuration space of one device. To speed things up,
we can program ATU only during first access.

This is mostly beneficial taking into account the previous patch that
adds 1ms delay after ATU reprogramming.

Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@epam.com>
Signed-off-by: Mykyta Poturai <mykyta_poturai@epam.com>
---
 xen/arch/arm/pci/pci-host-rcar4.c | 8 ++++++++
 1 file changed, 8 insertions(+)
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Patch

diff --git a/xen/arch/arm/pci/pci-host-rcar4.c b/xen/arch/arm/pci/pci-host-rcar4.c
index 3b97bf138a..3e3e073b09 100644
--- a/xen/arch/arm/pci/pci-host-rcar4.c
+++ b/xen/arch/arm/pci/pci-host-rcar4.c
@@ -367,6 +367,14 @@  static void dw_pcie_prog_outbound_atu(struct pci_host_bridge *pci, int index,
                                       int type, uint64_t cpu_addr,
                                       uint64_t pci_addr, uint64_t size)
 {
+    static uint64_t prev_addr = ~0;
+
+    /* Simple optimization to not-program ATU for every transaction */
+    if (prev_addr == pci_addr)
+        return;
+
+    prev_addr = pci_addr;
+
     __dw_pcie_prog_outbound_atu(pci, 0, index, type,
                                 cpu_addr, pci_addr, size);
 }