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. There is definitely precedents for this sort of behaviour, such as the ARM GICv2 probe code. M. -- Without deviation from the norm, progress is not possible.
