Re: Have my PA8800 back online... (serial port missing on v4.14)
On Fri, 2017-12-08 at 20:06 +0100, Helge Deller wrote:
> Adding the linux-serial mailing list:
Thanks for pointing to this out.
Details are below.
> > > Anyway, the *only* problem we have right now is, that the Linux
> > > kernel 4.14 doesn't detect all serial ports which were detected in
> > > earlier kernels.
> > > Thus the kernel will talk to the non-existant serial port at
> > > 0xfffffffff4050010 instead of 0xfffffffff4050000.
Wait, from this sentence you actually confirm that patch removes *non-
existant* ports.
Can you elaborate what you imply here?
> > > 4.13:
> > > [ 28.882849] Serial: 8250/16550 driver, 4 ports, IRQ sharing
> > > enabled
> > > [ 28.898720] 0000:e0:01.0: ttyS0 at MMIO 0xfffffffff4051000 (irq
> > > = 73, base_baud = 115200) is a 16450
> > > [ 28.934669] 0000:e0:01.1: ttyS1 at MMIO 0xfffffffff4050000 (irq
> > > = 73, base_baud = 115200) is a 16550A
> > > [ 28.963031] 0000:e0:01.1: ttyS2 at MMIO 0xfffffffff4050010 (irq
> > > = 73, base_baud = 115200) is a 16550A
> > > [ 28.984946] 0000:e0:01.1: ttyS3 at MMIO 0xfffffffff4050038 (irq
> > > = 73, base_baud = 115200) is a 16550A
>From here it looks like multi-function PCI device with two functions
with 1 + 3 serial ports each.
> > > ...but for v4.14.x only the following serial ports are detected:
> > > [ 28.671984] Serial: 8250/16550 driver, 4 ports, IRQ sharing
> > > enabled
> > > [ 28.708902] 0000:e0:01.1: ttyS0 at MMIO 0xfffffffff4050000 (irq
> > > = 73, base_baud = 115200) is a 16550A
> > > [ 28.731145] 0000:e0:01.1: ttyS1 at MMIO 0xfffffffff4050010 (irq
> > > = 73, base_baud = 115200) is a 16550A
I'm quite curious how ttyS0 and ttyS3 in previous run (old kernel)
appear.
> > >
> > >
> > > Maybe reverting this commit brings back the old behavior:
> > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> > > /commit/?id=7d8905d064058f4b65057e0101588f362f288bc0
> >
> > I'm unsure about this commit, it speaks more of avoiding duplicate
> > messages
> > for device enabling.
No, it's about trying IRQs twice, though it might be not fully clear
from commit message: the example there shows that IRQs are probed twice
and on some platforms it may be a problem.
>
> Reverting this commit:
>
> commit 7d8905d064058f4b65057e0101588f362f288bc0
> Author: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Date: Mon Jul 24 20:28:32 2017 +0300
>
> serial: 8250_pci: Enable device after we check black list
>
> indeed fixes the problem.
>
> After reverting, the serial port from the Diva card shows up as ttyS0
> (as before).
> With that patch applied, the serial port from the Diva card gets
> ignored and the previous ttyS1 port becomes ttyS0 which then breaks
> booting the parisc machine because the kernel expects the serial port
> on
> ttyS1.
> I'm not sure what the best way forward is.
> Fact is, that the patch above changes the behaviour and serial ports
> which were existant before suddenly vanish with kernel 4.14.
As stated in the commit message there "We can do this since PCI
specification requires class, device and vendor ID registers to be
always present in the configuration space."
So, my understanding that the patch reveals the issue with these ports.
(Of course, I agree this is regression and needs to be fixed ASAP)
> This following patch does work, and adds back the Diva serial port on
> parisc.
> Not sure if it's acceptable though.
For me it looks like the best quick solution right now.
The proper one sounds like a specific initialization routine for these
ports.
Send it as a formal patch and you may add
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
P.S. Sorry, we have no parisc hardware around to test.
>
> Helge
>
> diff --git a/drivers/tty/serial/8250/8250_pci.c
> b/drivers/tty/serial/8250/8250_pci.c
> index 0c101a7470b0..61319e968e8c 100644
> --- a/drivers/tty/serial/8250/8250_pci.c
> +++ b/drivers/tty/serial/8250/8250_pci.c
> @@ -3393,6 +3393,10 @@ static int
> serial_pci_is_class_communication(struct pci_dev *dev)
> * (Should we try to make guesses for multiport serial
> devices
> * later?)
> */
> + if (IS_ENABLED(CONFIG_PARISC) &&
> + (dev->class >> 8) == PCI_CLASS_COMMUNICATION_OTHER)
> + return 0;
> +
> if ((((dev->class >> 8) != PCI_CLASS_COMMUNICATION_SERIAL) &&
> ((dev->class >> 8) != PCI_CLASS_COMMUNICATION_MODEM)) ||
> (dev->class & 0xff) > 6)
--
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy
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