On Mon, Nov 14, 2016 at 08:26:42AM +0000, Gabriele Paoloni wrote: > Hi Liviu > [snip] > > > > > > > > Your idea is a good one, however you are abusing PCIBIOS_MIN_IO and > > you > > > > actually need another variable for "reserving" an area in the I/O > > space > > > > that can be used for physical addresses rather than I/O tokens. > > > > > > > > The one good example for using PCIBIOS_MIN_IO is when your > > > > platform/architecture > > > > does not support legacy ISA operations *at all*. In that case > > someone > > > > sets the PCIBIOS_MIN_IO to a non-zero value to reserve that I/O > > range > > > > so that it doesn't get used. With Zhichang's patch you now start > > > > forcing > > > > those platforms to have a valid address below PCIBIOS_MIN_IO. > > > > > > But if PCIBIOS_MIN_IO is 0 then it means that all I/O space is to be > > used > > > by PCI controllers only... > > > > Nope, that is not what it means. It means that PCI devices can see I/O > > addresses > > on the bus that start from 0. There never was any usage for non-PCI > > controllers > > So I am a bit confused... > From http://www.firmware.org/1275/bindings/isa/isa0_4d.ps > It seems that ISA buses operate on cpu I/O address range [0, 0xFFF]. > I thought that was the reason why for most architectures we have > PCIBIOS_MIN_IO equal to 0x1000 (so I thought that ISA controllers > usually use [0, PCIBIOS_MIN_IO - 1] ) First of all, cpu I/O addresses is an x86-ism. ARM architectures and others have no separate address space for I/O, it is all merged into one unified address space. So, on arm/arm64 for example, PCIBIOS_MIN_IO = 0 could mean that we don't care about ISA I/O because the platform does not support having an ISA bus (e.g.). > > For those architectures whose PCIBIOS_MIN_IO != 0x1000 probably > they are not fully compliant or they cannot fully support an ISA > controller...? Exactly. Not fully compliant is a bit strong, as ISA is a legacy feature and when it comes to PCI-e you are allowed to ignore it. Having PCIBIOS_MIN_IO != 0x1000 is a way to signal that you don't fully support ISA. > > As said before this series forbid IO tokens to be in [0, PCIBIOS_MIN_IO) > to allow special ISA controllers to use that range with special > accessors. > Having a variable threshold would make life much more difficult > as there would be a probe dependency between the PCI controller and > the special ISA one (PCI to wait for the special ISA device to be > probed and set the right threshold value from DT or ACPI table). > > Instead using PCIBIOS_MIN_IO is easier and should not impose much > constraint as [PCIBIOS_MIN_IO, IO_SPACE_LIMIT] is available to > the PCI controller for I/O tokens... What I am suggesting is to leave PCIBIOS_MIN_IO alone which still reserves space for ISA controller and add a PCIBIOS_MIN_DIRECT_IO that will reserve space for your direct address I/O on top of PCIBIOS_MIN_IO. Best regards, Liviu > > Thanks > > Gab > > > when PCIBIOS_MIN_IO != 0. That is what Zhichang is trying to do now and > > what > > I think is not the right thing (and not enough anyway). > > > > > so if you have a special bus device using > > > an I/O range in this case should be a PCI controller... > > > > That has always been the case. It is this series that wants to > > introduce the > > new meaning. > > > > > i.e. I would > > > expect it to fall back into the case of I/O tokens redirection rather > > than > > > physical addresses redirection (as mentioned below from my previous > > reply). > > > What do you think? > > > > I think you have looked too much at the code *with* Zhichang's patches > > applied. > > Take a step back and look at how PCIBIOS_MIN_IO is used now, before you > > apply > > the patches. It is all about PCI addresses and there is no notion of > > non-PCI > > busses using PCI framework. Only platforms and architectures that try > > to work > > around some legacy standards (ISA) or HW restrictions. > > > > Best regards, > > Liviu > > > > > > > > Thanks > > > > > > Gab > > > > > > > > > > > > > > For the general case you also have to bear in mind that > > PCIBIOS_MIN_IO > > > > could > > > > be zero. In that case, what is your "forbidden" range? [0, 0) ? So > > it > > > > makes > > > > sense to add a new #define that should only be defined by those > > > > architectures/ > > > > platforms that want to reserve on top of PCIBIOS_MIN_IO another > > region > > > > where I/O tokens can't be generated for. > > > > > > > > Best regards, > > > > Liviu > > > > > > > > > > > > > > > > > > > > > > > Your current version has > > > > > > > > > > > > > > > > if (arm64_extio_ops->pfout) > > > > \ > > > > > > > > arm64_extio_ops->pfout(arm64_extio_ops- > > > > >devpara,\ > > > > > > > > addr, value, sizeof(type)); > > > > \ > > > > > > > > > > > > > > > > Instead, just subtract the start of the range from the > > logical > > > > > > > > port number to transform it back into a bus-local port > > number: > > > > > > > > > > > > > > These accessors do not operate on IO tokens: > > > > > > > > > > > > > > If (arm64_extio_ops->start > addr || arm64_extio_ops->end < > > addr) > > > > > > > addr is not going to be an I/O token; in fact patch 2/3 > > imposes > > > > that > > > > > > > the I/O tokens will start at PCIBIOS_MIN_IO. So from 0 to > > > > > > PCIBIOS_MIN_IO > > > > > > > we have free physical addresses that the accessors can > > operate > > > > on. > > > > > > > > > > > > Ah, I missed that part. I'd rather not use PCIBIOS_MIN_IO to > > refer > > > > to > > > > > > the logical I/O tokens, the purpose of that macro is really > > meant > > > > > > for allocating PCI I/O port numbers within the address space of > > > > > > one bus. > > > > > > > > > > As I mentioned above, special devices operate on CPU addresses > > > > directly, > > > > > not I/O tokens. For them there is no way to distinguish.... > > > > > > > > > > > > > > > > > Note that it's equally likely that whichever next platform > > needs > > > > > > non-mapped I/O access like this actually needs them for PCI I/O > > > > space, > > > > > > and that will use it on addresses registered to a PCI host > > bridge. > > > > > > > > > > Ok so here you are talking about a platform that has got an I/O > > range > > > > > under the PCI host controller, right? > > > > > And this I/O range cannot be directly memory mapped but needs > > special > > > > > redirections for the I/O tokens, right? > > > > > > > > > > In this scenario registering the I/O ranges with the forbidden > > range > > > > > implemented by the current patch would still allow to redirect > > I/O > > > > > tokens as long as arm64_extio_ops->start >= PCIBIOS_MIN_IO > > > > > > > > > > So effectively the special PCI host controller > > > > > 1) knows the physical range that needs special redirection > > > > > 2) register such range > > > > > 3) uses pci_pio_to_address() to retrieve the IO tokens for the > > > > > special accessors > > > > > 4) sets arm64_extio_ops->start/end to the IO tokens retrieved in > > 3) > > > > > > > > > > So to be honest I think this patch can fit well both with > > > > > special PCI controllers that need I/O tokens redirection and with > > > > > special non-PCI controllers that need non-PCI I/O physical > > > > > address redirection... > > > > > > > > > > Thanks (and sorry for the long reply but I didn't know how > > > > > to make the explanation shorter :) ) > > > > > > > > > > Gab > > > > > > > > > > > > > > > > > If we separate the two steps: > > > > > > > > > > > > a) assign a range of logical I/O port numbers to a bus > > > > > > b) register a set of helpers for redirecting logical I/O > > > > > > port to a helper function > > > > > > > > > > > > then I think the code will get cleaner and more flexible. > > > > > > It should actually then be able to replace the powerpc > > > > > > specific implementation. > > > > > > > > > > > > Arnd -- ==================== | I would like to | | fix the world, | | but they're not | | giving me the | \ source code! / --------------- ¯\_(ツ)_/¯ -- 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
