On Tue, Apr 04, 2023 at 04:04:53PM +0200, Javier Martinez Canillas wrote: > Ondřej Jirman <megi@xxxxxx> writes: > > > On Tue, Apr 04, 2023 at 09:51:11AM +0200, Heiko Stübner wrote: > >> Hi, > >> > >> Am Montag, 3. April 2023, 19:59:37 CEST schrieb Javier Martinez Canillas: > >> > This baud rate is set for the device by mainline u-boot and is also what > >> > is set in the Pinebook Pro Device Tree, which is a device similar to the > >> > PinePhone Pro but with a different form factor. > >> > > >> > Otherwise, the baud rate of the firmware and Linux don't match by default > >> > and a 'console=ttyS2,1500000n8' kernel command line parameter is required > >> > to have proper output for both. > >> > >> The interesting question is always if this will break someone else's setup. > >> I've never really understood the strange setting of 1.5MBps, but on the > >> other hand it _is_ a reality on most boards. > > > > Normal users of the phone probably run with UART console disabled, because > > UART is muxed with audio jack output and to enable it they have to add > > console=ttyS2 to the kernel command line and flip a physical switch inside > > the phone. > > > > Fortunately, not sepcifying stdout-path baud rate in the options part > > of the string, will make the serial driver probe for the baud rate from > > the previous boot stage and make the user happy by keeping whatever was > > already set in the bootloader. > > > > As mentioned in the first email of this thread, I tried that but it didn't > work for me. Either using stdout-path = "serial2"; or stdout-path = &uart2; > gives me no serial output with console=ttyS2, I needed to specify the baud > rate explicitly (i.e: console=ttyS2,1500000n8). > > > https://elixir.bootlin.com/linux/latest/source/drivers/tty/serial/8250/8250_port.c#L3496 > > > > Is that helper really used by the serial driver in the PinePhone Pro? > (drivers/tty/serial/8250/8250_dw.c), I was meaning to dig why just ttyS2 > was not working but decided that could be a follow-up patch. It's called by univ8250_console_setup in 8250_core.c But looking at it again, this may only be used to match console=uart. https://elixir.bootlin.com/linux/latest/source/drivers/tty/serial/8250/8250_core.c#L638 Bummer. > Since chaging to 1.5 MBps seemed to have merits on its own, decided to > post this patch anyways in the meantime. > > > So we can make the kernel just keep the baudrate setup from the previous > > boot stage by: > > > > stdout-path = "serial2"; > > > > Did it work for you? Maybe I'm doing something silly but as mentioned it > didn't work for me with upstream u-boot. I was just eyeballing the code. I didn't test it. kind regards, o. > > regards, > > o. > > > > -- > Best regards, > > Javier Martinez Canillas > Core Platforms > Red Hat >
