On Wed, Mar 19, 2025 at 9:33 PM Heiner Kallweit <hkallweit1@xxxxxxxxx> wrote: > 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. Cool! So, can we just put a summary into the commit message of all findings, worries (or their absence)? -- With Best Regards, Andy Shevchenko
