On Fri, Jan 10, 2025 at 05:29:29PM +0530, Md Sadre Alam wrote: > On 1/10/2025 3:59 PM, Stephan Gerhold wrote: > > On Fri, Dec 20, 2024 at 03:12:03PM +0530, Md Sadre Alam wrote: > > > Avoid writing unavailable register in BAM-Lite mode. > > > BAM_DESC_CNT_TRSHLD register is unavailable in BAM-Lite > > > mode. Its only available in BAM-NDP mode. So only write > > > this register for clients who is using BAM-NDP. > > > > > > Signed-off-by: Md Sadre Alam <quic_mdalam@xxxxxxxxxxx> > > > > What are we actually fixing here? Which platform is affected? Is there a > > crash, reset, or incorrect behavior? > On SDX75, QPIC use BAM-Lite and as per HW description this > BAM_DESC_CNT_TRSHLD register is not available, and writing to this > SDX75 was hanging. > > > > We have had this code for years without reported issues, with both > > BAM-NDP and BAM-Lite instances. The register documentation on APQ8016E > > documents the BAM_DESC_CNT_TRSHLD register even for the BAM-Lite > > instance. There is a comment that it doesn't apply to BAM-Lite, but I > > would expect the written value just ends up being ignored in that case. > With older xPU it was being ignored but with new xPU its hanging. HW > team suggested don't write this register for BAM-Lite mode since its not > available. > > OK, thanks for the explanation. > > Also, there is not just BAM-NDP and BAM-Lite, but also plain "BAM". What > > about that one? Should we write to BAM_DESC_CNT_TRSHLD? > Apart from BAM-Lite this register available in all the BAM Please check again if we need to check for additional revision numbers for the non-NDP BAM types then. Or alternatively, change the check to write the register on if (!BAM-Lite) instead of if (BAM-NDP). That might be easier. Thanks, Stephan
