On Mon, Nov 30, 2020 at 09:05:48AM -0700, Rob Herring wrote: > On Sun, Nov 22, 2020 at 11:45 PM Jianjun Wang <jianjun.wang@xxxxxxxxxxxx> wrote: > > On Thu, 2020-11-19 at 14:28 -0600, Bjorn Helgaas wrote: > > > "Add new generation" really contains no information. And "mediatek" > > > is already used for the pcie-mediatek.c driver, so we should have a > > > new tag for this new driver. Include useful information in the > > > subject, e.g., > > > > > > PCI: mediatek-gen3: Add MediaTek Gen3 driver for MT8192 > > > > + writel(PCIE_CFG_HEADER_FORCE_BE(devfn, bus->number, bytes), > > > > + port->base + PCIE_CFGNUM_REG); > > > > + > > > > + *val = readl(port->base + PCIE_CFG_OFFSET_ADDR + (where & ~0x3)); > > > > > > These look like they need to be atomic, since you need a writel() > > > followed by a readl(). > > > > > > pci_lock_config() (used in pci_bus_read_config_*(), etc) uses the > > > global pci_lock for this unless CONFIG_PCI_LOCKLESS_CONFIG is set. > > > > > > But I would like to eventually move away from this implicit dependency > > > on pci_lock. If you need to make this atomic, can you add the > > > explicit locking here, so there's a clear connection between the lock > > > and the things it protects? > > > > Sure, I will split it to a map_bus() function and use the standard > > pci_generic_config_read32/write32 functions as Rob's suggestion. I think > > the potential risks of atomic read/write can be avoided. > > The generic functions have no effect on atomicity, but using them does > make it easier to find the non-atomic cases. > > I'm not sure that having host drivers do their own locking is the best > approach. That's a recipe for more cleanups. It's a common enough > issue that I think it's better if we have locking done in 1 place. > Then host drivers can simply say if they need locking or not via some > bus flag. Yeah, you may be right. I guess we don't have to make it an issue for this patch; we do have pci_lock that protects this, whether the write/read occurs in the driver or in pci_generic_config_read32/write32. Bjorn
