Hi Lukas, > On Thu, Dec 16, 2021 at 09:36:20PM +0100, Ulrich Teichert wrote: > > > struct uart_8250_port contains mcr_mask and mcr_force members whose > > > sole purpose is to work around an alpha-specific quirk. This code > > > doesn't belong in the core where it is executed by everyone else, > > > so move it to a proper ->set_mctrl callback which is used on alpha only. > [...] > > > The quirk applies to non-PCI alphas and arch/alpha/Kconfig specifies > > > "select FORCE_PCI if !ALPHA_JENSEN". So apparently the only affected > > > machine is the EISA-based Jensen that Linus was working on back then: > [...] > > > Up until now the quirk is not applied unless CONFIG_PCI is disabled. > > > If users forget to do that, the serial ports aren't usable on Jensen > > > and the machine may not boot in the first place. Avoid by confining > > > the quirk to CONFIG_ALPHA_JENSEN instead. > > > > Wouldn't that mean that you can't use a generic Alpha kernel on the Jensen > > anymore? CONFIG_ALPHA_JENSEN is only set if you specifically select the > > Jensen as target, not when you build a generic kernel. That would be a step > > back in my opinion, as the Debian generic kernel from debian-ports did > > as least boot up on real hardware and the serial console worked just fine > > The generic Alpha kernel has CONFIG_PCI=y, so the quirk is not applied, > both with and without the present patch. Right. > You should be able to trigger the lockup that the quirk seeks to avoid > by closing the tty of either of the serial ports. E.g., if you're using > the serial console, "cat" something to the other serial port's tty. > That will clear TIOCM_OUT2 in serial8250_do_shutdown() and should thus > provoke the lockup. Alternatively, compile and run the little program > below on the Jensen. (Pass a serial port tty as argument.) > > Should you not be able to reproduce the lockup, then the quirk wouldn't > be necessary anymore and could be removed. [del] Thanks for the explanation and the reproducer program. I tried yesterday to install a recent Linux-Alpha distribution on any of my Alphas to be able to build natively and check my self-build kernels before burning a CD-ROM, but I failed. Neither gentoo nor Debian nor T2 was installable on my Miatas (the Personal Workstations) or my Avanti (AlphaStation 400), either failing to boot or recognizing the disks or the CD-ROM, or switching to a framebuffer which did not work or just dying on the hardware detection. That was a bit frustrating, but I have to follow plan B now and do cross-builds from amd_x64 to Alpha - that's easy for the kernel (infact, that's what I've been doing from the start), but generating something bootable that way is a challenge and needs more time than I usually have during the week, but I will tackle it over my xmas vacation, CU, Uli -- Dipl. Inf. Ulrich Teichert|e-mail: Ulrich.Teichert@xxxxxx | Listening to: Stormweg 24 |Eat Lipstick: Dirty Little Secret, The Baboon Show: 24539 Neumuenster, Germany|Work Work Work, The Bellrays: Bad Reaction
