On September 17, 2022 11:07:18 AM GMT+01:00, "Maciej W. Rozycki" <macro@xxxxxxxxxxx> wrote: >Hi, > > A recent change has added a SERIAL_8250_16550A_VARIANTS option, which >lets one request the 8250 driver not to probe for 16550A device features >so as to reduce the driver's device startup time in virtual machines. >This has turned out problematic to a more recent update for the OxSemi >Tornado series PCIe devices, whose new baud rate generator handling code >actually requires switching hardware into the enhanced mode for correct >operation, which actually requires 16550A device features to have been >probed for. > > This small patch series fixes the issue by letting individual device >subdrivers to request full 16550A device feature probing by means of a >flag regardless of the SERIAL_8250_16550A_VARIANTS setting chosen. > > The changes have been verified with an OXPCIe952 device, in the native >UART mode and a 64-bit RISC-V system as well as in the legacy UART mode >and a 32-bit x86 system. Seems reasonable to me, as long as the flag is only set by drivers that know they've found their hardware.
