On Thu, Apr 17, 2025 at 04:07:51PM +0800, Hans Zhang wrote: > On 2025/4/17 15:48, Niklas Cassel wrote: > > Hi Niklas and Shawn, > > Thank you very much for your discussion and reply. > > I tested it on RK3588 and our platform. By setting pci=pcie_bus_safe, the > maximum MPS will be automatically matched in the end. > > So is my patch no longer needed? For RK3588, does the customer have to > configure CONFIG_PCIE_BUS_SAFE or pci=pcie_bus_safe? > > Also, for pci-meson.c, can the meson_set_max_payload be deleted? I think the only reason why this works is because pcie_bus_configure_settings(), in the case of pcie_bus_config == PCIE_BUS_SAFE, will walk the bus and set MPS in the bridge to the lowest of the downstream devices: https://github.com/torvalds/linux/blob/v6.15-rc2/drivers/pci/probe.c#L2994-L2999 So Hans, if you look at lspci for the other RCs/bridges that don't have any downstream devices connected, do they also show DevCtl.MPS 256B or do they still show 128B ? One could argue that for all policies (execept for maybe PCIE_BUS_TUNE_OFF), pcie_bus_configure_settings() should start off by initializing DevCtl.MPS to DevCap.MPS (for the bridge itself), and after that pcie_bus_configure_settings() can override it depending on policy, e.g. set MPS to 128B in case of pcie_bus_config == PCIE_BUS_PEER2PEER, or walk the bus in case of pcie_bus_config == PCIE_BUS_SAFE. That way, we should be able to remove the setting for pci-meson.c as well. Bjorn, thoughts? Kind regards, Niklas
