linux-kernel - Re: [RFC PATCH] always probe UART HW when options are not specified

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Message-ID: <5693C52B.90003@laposte.net>
Date:	Mon, 11 Jan 2016 16:07:23 +0100
From:	Sebastian Frias <sf84@...oste.net>
To:	Peter Hurley <peter@...leysoftware.com>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-serial@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	mason <slash.tmp@...e.fr>,
	Måns Rullgård <mans@...sr.com>
Subject: Re: [RFC PATCH] always probe UART HW when options are not specified

On 12/22/2015 06:56 PM, Sebastian Frias wrote:
> On 12/21/2015 05:50 PM, Sebastian Frias wrote:
>>> You need to use the format documented in
>>> Documentation/kernel-parameters.text:
>>>
>>>     console=    [KNL] Output console device and options.
>>>
>>>         uart[8250],io,<addr>[,options]
>>>         uart[8250],mmio,<addr>[,options]
>>>         uart[8250],mmio16,<addr>[,options]
>>>         uart[8250],mmio32,<addr>[,options]
>>>         uart[8250],0x<addr>[,options]
>>>             Start an early, polled-mode console on the 8250/16550
>>>             UART at the specified I/O port or MMIO address,
>>>             switching to the matching ttyS device later.
>>>             MMIO inter-register address stride is either 8-bit
>>>             (mmio), 16-bit (mmio16), or 32-bit (mmio32).
>>>             If none of [io|mmio|mmio16|mmio32], <addr> is assumed
>>>             to be equivalent to 'mmio'. 'options' are specified in
>>>             the same format described for ttyS above; if unspecified,
>>>             the h/w is not re-initialized.
>>>
>>> The iotype and the uart address are not options.
>>
>> Do you mean they are mandatory?
>> How do they relate to the keys present on the DT? Because the device is
>> already described in the DT:
>>
>>          uart: serial@...00 {
>>              compatible = "ralink,rt2880-uart";
>>              reg = <0x10700 0x30>;
>>              interrupts = <1 IRQ_TYPE_LEVEL_HIGH>;
>>              clock-frequency = <7372800>;
>>              reg-shift = <2>;
>>          };
>>
>> Are we supposed to duplicate such information (ie: addr) in the
>> commandline as well?
>>
>
> By the way, I tried using the following command line
> 'console=uart,mmio32,0x10700,115200n8r mem=256M earlyprintk debug
> ignore_loglevel' but I think I'm still missing something regarding this,
> because it does not work, here's a log of Linux 4.1.13+:
>
>
> 1: [arch/arm/kernel/setup.c:932] setup_arch(): r1 = 0xf34, r2 =
> 0x803b3b50, cmdline ''
> 1: [arch/arm/kernel/devtree.c:195] arch_get_next_mach(): infoBegin
> 0xc024faac, mdesc 0xc024faac
> 1: [arch/arm/kernel/devtree.c:195] arch_get_next_mach(): infoBegin
> 0xc024faac, mdesc 0xc024fb14
> 1: [drivers/of/fdt.c:106] of_fdt_is_compatible(): sigma,tango4 vs
> sigma,vantage-1172
> 1: [arch/arm/kernel/devtree.c:195] arch_get_next_mach(): infoBegin
> 0xc024faac, mdesc 0xc024fb7c
> 1: [drivers/of/fdt.c:749] of_flat_dt_match_machine(): Machine model:
> Sigma Designs SMP8758 Vantage-1172 Rev E1
> 1: [arch/arm/kernel/devtree.c:256] setup_machine_fdt(): about to call
> early_init_dt_scan_nodes
> 1: [drivers/of/fdt.c:1057] early_init_dt_scan_nodes(): bootcmdline ''
> 1: [drivers/of/fdt.c:1062] early_init_dt_scan_nodes(): bootcmdline after
> of_scan_flat_dt 'console=uart,mmio32,0x10700,115200n8r mem=256M
> earlyprintk debug ignore_loglevel'
> 1: [arch/arm/kernel/setup.c:946] setup_arch(): using DT at r2
> 1: [arch/arm/kernel/setup.c:949] setup_arch(): machine name Sigma Tango DT
> 1: [arch/arm/kernel/setup.c:967] setup_arch(): before parse_early_param
> 1: [init/main.c:468] parse_early_param(): bootcmdline
> 'console=uart,mmio32,0x10700,115200n8r mem=256M earlyprintk debug
> ignore_loglevel'
> 1: [init/main.c:473] parse_early_param(): mark
> 1: [init/main.c:428] do_early_param(): enter with: 'console'
> 'uart,mmio32,0x10700,115200n8r'
> 1: [init/main.c:446] do_early_param(): 'earlycon', setup_func 0xc024b868
> 1: [drivers/tty/serial/earlycon.c:214] param_setup_earlycon():
> 'uart,mmio32,0x10700,115200n8r'
> 1: [drivers/tty/serial/earlycon.c:181] setup_earlycon():
> 'uart,mmio32,0x10700,115200n8r'
> 1: [drivers/tty/serial/earlycon.c:132] register_earlycon():
> 'mmio32,0x10700,115200n8r' 'uart'
> 1: [drivers/tty/serial/earlycon.c:86] parse_options():
> 'mmio32,0x10700,115200n8r'
> 1: [drivers/tty/serial/earlycon.c:91] parse_options(): addr 0x00010700,
> options '115200n8r'
> 1: [drivers/tty/serial/earlycon.c:117] parse_options(): Early serial
> console at MMIO32 0x10700 (options '115200n8r')
> 1: [drivers/tty/serial/earlycon.c:138] register_earlycon(): '(null)'
> 1: [drivers/tty/serial/earlycon.c:62] earlycon_map(): paddr 0x00010700
> size 64
>
> As you can see, now that the options are more complete, the match for
> "earlycon" succeeds, but it does not work, the last log is in
> earlycon_map() function.
> When using just "console=uart", the "earlycon" match will fail but a
> match for "earlyprink" will succeed. That one will hook printch() from
> the arch-dependent code to a somewhat simpler 'earlycon'
> (arch/arm/kernel/early_printk.c).
>
> I think the code is the same on mainline.
>
> Also, regarding my previous question about using a HW described in DT
> for earlycon, I noticed there's a of_setup_earlycon() in
> drivers/tty/serial/earlycon.c but that is hooked to
> drivers/of/fdt.c:setup_of_earlycon() which is not called. I do have
> CONFIG_SERIAL_EARLYCON=y.
>
> I also have a similar issue (ie: get blocked right after the call to
> earlycon_map function, log is obviously different from above) if attempt
> to use of_setup_earlycon.
> My DT has roughly:
>
>      aliases {
>          serial0 = &uart;
>      };
>
>      chosen {
>             bootargs = "earlycon console mem=256M earlyprintk debug
> ignore_loglevel";
>             stdout-path = "serial0:115200n8";
>      };
>
>      uart: serial@...00 {
>          compatible = "ralink,rt2880-uart";
>          reg = <0x10700 0x30>;
>          interrupts = <1 IRQ_TYPE_LEVEL_HIGH>;
>          clock-frequency = <7372800>;
>          reg-shift = <2>;
>      };
>
>
> and then I hack drivers/tty/serial/8250/8250_early.c by adding:
>
>      OF_EARLYCON_DECLARE(rt2880, "ralink,rt2880-uart",
> early_serial8250_setup);
>
> at the end of the file, trying to mimic commit
> d05f15707bb7659d2b863fafa1a918f286d74a63
>
> I'm still trying to figure out the right bootargs, so that's why both
> "earlycon" and "console" are there. Suggestions welcome.
>

Does anybody has comments or suggestions regarding this thread and the 
issue above?