Hi Arnd > -----Original Message----- > From: Arnd Bergmann [mailto:arnd@xxxxxxxx] > Sent: 23 September 2016 14:43 > To: Gabriele Paoloni > Cc: zhichang.yuan; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; > devicetree@xxxxxxxxxxxxxxx; lorenzo.pieralisi@xxxxxxx; minyard@xxxxxxx; > linux-pci@xxxxxxxxxxxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx; John Garry; > will.deacon@xxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Yuanzhichang; > Linuxarm; xuwei (O); linux-serial@xxxxxxxxxxxxxxx; > benh@xxxxxxxxxxxxxxxxxxx; zourongrong@xxxxxxxxx; liviu.dudau@xxxxxxx; > kantyzc@xxxxxxx > Subject: Re: [PATCH V3 2/4] ARM64 LPC: LPC driver implementation on > Hip06 > > On Friday, September 23, 2016 10:23:30 AM CEST Gabriele Paoloni wrote: > > Hi Arnd > > > > > -----Original Message----- > > > From: Arnd Bergmann [mailto:arnd@xxxxxxxx] > > > Sent: 23 September 2016 10:52 > > > To: zhichang.yuan > > > Cc: Gabriele Paoloni; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; > > > devicetree@xxxxxxxxxxxxxxx; lorenzo.pieralisi@xxxxxxx; > minyard@xxxxxxx; > > > linux-pci@xxxxxxxxxxxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx; John Garry; > > > will.deacon@xxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Yuanzhichang; > > > Linuxarm; xuwei (O); linux-serial@xxxxxxxxxxxxxxx; > > > benh@xxxxxxxxxxxxxxxxxxx; zourongrong@xxxxxxxxx; > liviu.dudau@xxxxxxx; > > > kantyzc@xxxxxxx > > > Subject: Re: [PATCH V3 2/4] ARM64 LPC: LPC driver implementation on > > > Hip06 > > > > > > On Friday, September 23, 2016 12:27:17 AM CEST zhichang.yuan wrote: > > > > For this patch sketch, I have a question. > > > > Do we call pci_address_to_pio in arch_of_address_to_pio to get > the > > > > corresponding logical IO port > > > > for LPC?? > > > > > > > > > No, of course not, that would be silly: > > > > > > The argument to pci_address_to_pio() is a phys_addr_t, and we we > don't > > > have one because there is no address associated with your PIO, that > > > is the entire point of your driver! > > > > > > Also, we already know the mapping because this is what the inb/outb > > > workaround is looking at, so there is absolutely no reason to call > it > > > either. > > > > Ok assume that we do not call pci_address_to_pio() for the ISA bus... > > The LPC driver will register its phys address range in io_range_list, > > then the IPMI driver probe will retrieve its physical address calling > > of_address_to_resource and will use the indirect io to access this > > address. > > > > From the perspective of the indirect IO function the input parameter > > is an unsigned long addr that (now) can be either: > > 1) an IO token coming from a legacy pci device > > 2) a phys address that lives on the LPC bus > > > > These are conceptually two separate address spaces (and actually they > > both start from 0). > > Why? Any IORESOURCE_IO address always refers to the logical I/O port > range in Linux, not the physical address that is used on a bus. > > > If the input parameter can live on different address spaces that are > > overlapped, even if I save the used LPC range in arm64_extio_ops- > >start/end > > there is no way for the indirect IO to tell if the input parameter is > > an I/O token or a phys address that belongs to LPC... > Assume that in the probe function the LPC drivers calls pci_register_io_range for the LPC cpu address range (0 to PCIBIOS_MIN_I0) and does not scan the children DT nodes. Consider for example the ipmi driver: When the reg property is read to retrieve the ipmi <<i/o port>> in http://lxr.free-electrons.com/source/drivers/char/ipmi/ipmi_si_intf.c#L2622 if we do not call pci_address_to_pio in __of_address_to_resource the input parameter of inb/outb will be the cpu address of the ipmi (not translated to a unique token id). So inb/outb at this stage can be called passing either a cpu address or a token io port. If we set arm64_extio_ops->start/end to 0 and PCIBIOS_MIN_I0 respectively we still cannot tell inside inb/outb if the passed address is a token or an LPC cpu address as the ipmi cpu address can overlap with another device I/O token... My suggestion is to call pci_address_to_pio even for devices living on the LPC bus; then in the LPC probe we set arm64_extio_ops->start/end to the I/O tokens that correspond to the LPC cpu address range (in the LPC probe function we call pci_address_to_pio after we have called pci_register_io_range); finally in inb/outb we know that we can get only an I/O token as input parameter and we check it against arm64_extio_ops->start/end to decide whether to call the LPC accessors or readb/writeb... > The start address is the offset: if you get an address between 'start' > and 'end', you subtract the 'start' from it, and use that to call > the registered driver function. That works because we can safely > assume that the bus address range that the LPC driver registers starts > zero. Sorry I cannot follow what you said here above: <<if you get an address between 'start' and 'end'>>...in which function? Thanks Gab > > Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
