On 19.03.2025 09:23, Andy Shevchenko wrote: > On Wed, Mar 19, 2025 at 9:17 AM Heiner Kallweit <hkallweit1@xxxxxxxxx> wrote: >> On 19.03.2025 00:22, Andi Shyti wrote: >>> On Wed, Mar 19, 2025 at 12:18:47AM +0200, Andy Shevchenko wrote: >>>> Wed, Mar 12, 2025 at 08:07:23PM +0100, Heiner Kallweit kirjoitti: > > >>>>> Switch to iomapped register access as a prerequisite for adding >>>>> support for MMIO register access. >>>> >>>> I believe that I at least discussed the similar change a few years ago or even >>>> proposed a one. The problem here is that *_p() variants of IO port accessors >>>> are not the same as non-_p ones. And commit message is kept silent about >>>> possible consequences of this change. >>>> >>>> So, at bare minumum it would be good to test for some period of time before >>>> going for it. >>> >>> How would you do it? >> >> Documentation/driver-api/device-io.rst states that the artificially delayed >> _p versions were needed on ISA devices. And in general I didn't find any hint >> that the non-delayed versions ever caused issues on PCI devices. > > At least put this in the commit message. It will show that you were aware of _p. > >> On my system using the non-delayed version works fine, but I can't say 100% >> that it's the same for the very first (> 25 yrs ago) chipsets supported by i801. >> >> Likely users with old systems don't run -next kernels, therefore leaving >> this change a full cycle in -next may not really help. We can argue that >> we have the -rc period for testing (and reverting if needed). > > My main concern is to make no regressions for most currently used > cases, that's why one cycle in Linux Next is better than none. > Even ICH7 datasheet from 2012 mentions that SMBus register space is also memory-mapped. So all systems from at least the last 10 yrs should use MMIO instead of PMIO now, and therefore not be affected by switching to non-delayed PMIO access. This should significantly reduce the risk you're referring to.
