On Mon, 28 Aug 2023 at 13:04, Marc Zyngier <maz@xxxxxxxxxx> wrote: > > On Mon, 28 Aug 2023 10:46:10 +0100, > Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx> wrote: > > > > On Mon, 28 Aug 2023 at 12:36, Maulik Shah (mkshah) > > <quic_mkshah@xxxxxxxxxxx> wrote: > > > > > > Hi Dmitry, > > > > > > This patch may be useful if there was a case where some PDCs don't have > > > version register populated/available, > > > In all PDC versions, version register is always available but due to reg > > > size not good enough in device tree for SM8150 it failed to read. > > > > > > reg size in device node must be expanded if its too small to access all > > > registers and i think > > > additional check in driver to check if size is good enough would not be > > > of much use. > > > > Unfortunately, it doesn't work this way. DT files are ABI. Even if we > > change the DT, the kernel should continue working with the older > > version. > > Thus, we have to add such bandaid code, which will keep the kernel > > from crashing if old DT was used. > > You're missing the point: all existing PDC HW have version register. > The fact that the DT is crap doesn't invalidate this simple fact. It > is thus perfectly possible for the driver to *ignore* the crap and do > the right thing by expanding the size of the mapping, rather than > falling back to the non-versioned code. Ah. Interesting idea. If that's the overall consensus I can send v2 doing this. Not sure what is better though. > > There is definitely precedents for this sort of behaviour, such as the > ARM GICv2 probe code. -- With best wishes Dmitry
