On 28.08.2023 12:04, Marc Zyngier 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. I wasn't sure if this would cross the "too hacky" boundary, but if you're fine with it, I'll happily ack this approach. Konrad
