On 2017-03-09 09:30, Ralf Ramsauer wrote: > On 03/08/2017 11:28 PM, Jan Kiszka wrote: >> On 2017-03-09 02:07, Ralf Ramsauer wrote: >>> Hi Claudio, >>> >>> On 03/08/2017 01:37 PM, Claudio Scordino wrote: >>>> Hi Ralf, >>>> >>>> sorry, I didn't recall the discussion on list. >>>> >>>> Using the config currently generated by "jailhouse config create", our >>>> i7 prints junk on the console, unless we manually add such divider. >>>> If this is the intended behavior and we are supposed to add it, then I'm >>>> fine. >>>> However, I'm afraid that several newbies could flood the list >>>> complaining that their serial "doesn't work" if we don't properly >>>> document such information. >>> Usually we make the assumption that Linux initialises UARTs beforehand. >> >> We do this on ARM, we didn't do this on x86 prior to that commit as >> Claudio pointed out. >> >> ARM is trickier to configure because we tend to have different dividers >> on the different boards. For the x86 standard UARTs, we know the >> divider, though. As long as the right value is applied, >> re-initialization should cause no harm and will cover the case Linux is >> configured to not use the UART at all. > That's the point. As long as the 'right value' is applied. And if the > right value is applied, nothing will happen and we can leave it out :) > > As Claudio received garbage on his serial line, I assume that the serial > port was simply not configured with 115200 baud on Linux side before and > as the UART is typically root-shared with Linux, enforcing 115200 baud > in Jailhouse leads to corrupt settings in Root-Linux. If the divider > would have been 0 (i.e., the device would not have been initialised at > all), then he would not have received anything. > > By default, many distributions spawn a console on the serial line(s) > that are configured with a baudrate different than 115200 (commonly > 38400 or 9600). Better change those settings than overriding them.
Hmm, my experience is that x86 distros leave the PC UARTs alone by default, unless you tell them to use one. Which one does that differently? > > I understand the divider in the system config as an explicit setting > that should only be used if the serial line is not handled by Linux, > which could be detected by 'jailhouse config create'. And we have > 'jailhouse console' that will work independent of the baudrate. > > I would rather suggest a FAQ and recommend to check the baudrate of the > serial device before starting jailhouse than overriding Linux settings > (by default). > > Ralf >> >> Jan >> >>> Setting the divider (or enabling clock gates) is as far as I understand >>> (Jan, please correct me if I'm wrong) an optional feature that can be >>> used, if the root cell doesn't properly setup UARTs (e.g., because it's >>> missing the driver). >>> >>> What happens if you 'stty -F /dev/ttyS0 115200' before enabling >>> jailhouse? Still garbage? Or just 'stty -F /dev/ttyS0' to see what >>> baudrate your device is currently set to before enabling Jailhouse. >>> >>> You told me off-list that you receive garbage on your serial line -- so >>> I suppose the problem is that Linux set your baudrate just to something >>> else than 115k2. Junk on the serial line is in almost all cases baudrate >>> related. >>> >>> Ralf >>>> >>>> Many thanks and best regards, >>>> >>>> Claudio >>>> >>>> 2017-03-08 20:03 GMT+01:00 Ralf Ramsauer <[email protected]>: >>>>> On 03/08/2017 07:55 AM, Jan Kiszka wrote: >>>>>> On 2017-03-08 15:57, Claudio Scordino wrote: >>>>>>> This patch fixes a regression introduced by commit >>>>>>> 2a7c8733b6a3d47fb507eca4de5a33433199424c >>>>>>> which by default does not initialize the UART divider to 0x1 >>>>>>> on the x86 platform. >>>>> Isn't this intended behaviour? I remember that we had discussions on >>>>> that on the list, and according to the commit message, >>>>> >>>>> ... >>>>> If the divider is zero, the hypervisor will skip UART initialisation and >>>>> assume that the UART was already initialised by Linux. >>>>> ... >>>>> >>>>> All we do on x86 is to skip those four instructions if the divider is >>>>> zero: >>>>> uart_reg_out(UART_LCR, UART_LCR_DLAB); >>>>> uart_reg_out(UART_DLL, divider & 0xff); >>>>> uart_reg_out(UART_DLM, (divider >> 8) & 0xff); >>>>> uart_reg_out(UART_LCR, UART_LCR_8N1); >>>>> >>>>> which should in deed be done by Linux before, if this is what we define >>>>> default behaviour. >>>>>>> >>>>>>> Signed-off-by: Claudio Scordino <[email protected]> >>>>>>> Signed-off-by: Michele Pes <[email protected]> >>>>>>> --- >>>>>>> tools/root-cell-config.c.tmpl | 1 + >>>>>>> 1 file changed, 1 insertion(+) >>>>>>> >>>>>>> diff --git a/tools/root-cell-config.c.tmpl >>>>>>> b/tools/root-cell-config.c.tmpl >>>>>>> index 11956b7..a971f56 100644 >>>>>>> --- a/tools/root-cell-config.c.tmpl >>>>>>> +++ b/tools/root-cell-config.c.tmpl >>>>>>> @@ -62,6 +62,7 @@ struct { >>>>>>> }, >>>>>>> .debug_console = { >>>>>>> .address = 0x3f8, >>>>>>> + .divider = 0x1, >>>>> I'd rather insert this as a comment. >>>>>>> .flags = JAILHOUSE_CON1_TYPE_UART_X86 | >>>>>>> JAILHOUSE_CON1_FLAG_PIO | >>>>>>> JAILHOUSE_CON2_TYPE_ROOTPAGE, >>>>>>> >>>>>> >>>>>> We probably want this fixed for the in-tree x86 configs as well, namely >>>>>> >>>>>> configs/f2a88xm-hd3.c >>>>>> configs/imb-a180.c >>>>>> configs/qemu-vm.c >>>>> Just tested qemu, on my VM everything works fine. >>>>> >>>>> Ralf >>>>>> >>>>>> Ralf, am I right? >>>>>> >>>>>> Jan >>>>>> >>>> >>>> >>>> >> >> -- Siemens AG, Corporate Technology, CT RDA ITP SES-DE Corporate Competence Center Embedded Linux -- You received this message because you are subscribed to the Google Groups "Jailhouse" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
