| Message ID | e01e6aeba461001093b0da9af4c14b922049080a.1741596512.git.mykyta_poturai@epam.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Add support for R-Car Gen4 PCI host controller | expand |
On 11.03.25 12:24, Mykyta Poturai wrote: > 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> > --- > v1->v2: > * rebased > --- > xen/arch/arm/pci/pci-designware.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/xen/arch/arm/pci/pci-designware.c b/xen/arch/arm/pci/pci-designware.c > index def2c12d63..cec52cf81a 100644 > --- a/xen/arch/arm/pci/pci-designware.c > +++ b/xen/arch/arm/pci/pci-designware.c > @@ -272,6 +272,14 @@ 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) > { First, using (hiding) static var inside the function deserve big, fat comment on why and what. > + static uint64_t prev_addr = ~0; Second, from an experience, static vars in functions is source of potential problems, it's kinda land mines in code. For example, lets assume there are two pci_host_bridge instances in Xen and they are accessed concurrently. Best to get rid of static var here - may be move in pci_host_bridge, like cached_pci_addr? not sure > + > + /* 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); > } BR, -grygorii
diff --git a/xen/arch/arm/pci/pci-designware.c b/xen/arch/arm/pci/pci-designware.c index def2c12d63..cec52cf81a 100644 --- a/xen/arch/arm/pci/pci-designware.c +++ b/xen/arch/arm/pci/pci-designware.c @@ -272,6 +272,14 @@ 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); }