sh-sci: Add CONFIG_SERIAL_EARLYCON support
Subsystems (2)
Yoshinori Sato
maintainerRFC 1/1 sh-sci: Add CONFIG_SERIAL_EARLYCON support
Hello.
"earlyprintk" is architecture specific option. I think general "earlycon" option support more better.
--- drivers/tty/serial/Kconfig | 6 ++++ drivers/tty/serial/sh-sci.c | 70 +++++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 73 insertions(+), 3 deletions(-)
drivers/tty/serial/Kconfig +6 -0
@@ -741,6 +741,12 @@ config SERIAL_SH_SCI_CONSOLE depends on SERIAL_SH_SCI=y select SERIAL_CORE_CONSOLE +config SERIAL_SH_SCI_EARLYCON + bool "Support for early console on SuperH SCI(F)" + depends on SERIAL_SH_SCI=y + select SERIAL_CORE_CONSOLE + select SERIAL_EARLYCON + config SERIAL_SH_SCI_DMA bool "DMA support" depends on SERIAL_SH_SCI && SH_DMAE
drivers/tty/serial/sh-sci.c +67 -3
96 lines not on this page · raw message
Signature · 1 line
2.1.4
Hi Sato-san, Arnd,
Quoted 2 lines · Yoshinori Sato
"earlyprintk" is architecture specific option. I think general "earlycon" option support more better.
Thanks for your patch!
I finally gave it a try on shmobile. Sorry for taking that long...
Despite claims from a few months ago:
Quoted 2 lines · Arnd Bergmann
I think a number of people have expressed that they'd rather get rid of the
DEBUG_LLlist in the long run, now that we have earlycon working. If we
earlycon doesn't seem to be ready on arm.
Without "[PATCH v5] ARM: early fixmap support for earlycon"
(https://lkml.org/lkml/2015/8/11/532), it hangs in ioremap(), as called from earlycon_map().
Quoted 40 lines
drivers/tty/serial/sh-sci.c +17
-2-#ifdef CONFIG_SERIAL_SH_SCI_CONSOLE +#if defined(CONFIG_SERIAL_SH_SCI_CONSOLE ) || defined(CONFIG_SERIAL_EARLYCON )static void serial_console_putchar (struct uart_port *port,int ch) {sci_poll_put_char (port, ch);@@ -2359,9 +2360,12 @@ static void serial_console_write(struct console *co, const char *s,int locked =1 ;local_irq_save (flags); +#if defined(SUPPORT_SYSRQ )if (port->sysrq) locked =0 ; -else if (oops_in_progress) + else +#endif +if (oops_in_progress) locked =spin_trylock (&port->lock);else spin_lock (&port->lock);@@ -2719,6 +2723,66 @@ static void __exit sci_exit(void)early_platform_init_buffer ("earlyprintk" , &sci_driver, early_serial_buf,ARRAY_SIZE (early_serial_buf));#endif +#ifdef CONFIG_SERIAL_EARLYCON +static struct __init plat_sci_port port_cfg; + +static int __init early_console_setup (struct earlycon_device *device, +int type) +{ +if (!device->port.membase) +return -ENODEV ; + + device->port.serial_in = sci_serial_in; + device->port.serial_out = sci_serial_out; + device->port.type = type;
drivers/tty/serial/sh-sci.c static void __exit sci_exit(void) · line 2747
Quoted 10 lines
drivers/tty/serial/sh-sci.c +10
-0+memcpy (&sci_ports[0 ].port, &device->port,sizeof (struct uart_port )); + sci_ports[0 ].cfg = &port_cfg; + sci_ports[0 ].cfg->type = type; +sci_probe_regmap (sci_ports[0 ].cfg); + port_cfg.scscr =SCSCR_RE |SCSCR_TE ; +sci_serial_out (&sci_ports[0 ].port,SCSCR , port_cfg.scscr); + + device->con->write = serial_console_write; +return 0 ; +}
Earlycon cannot use serial_console_write(), as it takes an uninitialized spinlock():
BUG: spinlock bad magic on CPU#0, swapper/0 lock: sci_ports+0x0/0x35c0, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0 CPU: 0 PID: 0 Comm: swapper Not tainted 4.2.0-rc6-koelsch-04464-g15cd6b1126aee571 #1525 Hardware name: Generic R8A7791 (Flattened Device Tree) Backtrace: [<c00138b4>] (dump_backtrace) from [<c0013aac>] (show_stack+0x18/0x1c) r6:600001d3 r5:c0e6d268 r4:00000000 r3:00200000 [<c0013a94>] (show_stack) from [<c045fe3c>] (dump_stack+0x78/0x94) [<c045fdc4>] (dump_stack) from [<c006f61c>] (spin_dump+0x80/0x94) r4:00000000 r3:00000000 [<c006f59c>] (spin_dump) from [<c006f65c>] (spin_bug+0x2c/0x30) r5:c0e6d268 r4:c057cfe7 [<c006f630>] (spin_bug) from [<c006f6e8>] (do_raw_spin_lock+0x28/0x198) r5:c0e6d268 r4:c0e6d268 [<c006f6c0>] (do_raw_spin_lock) from [<c0465654>] (_raw_spin_lock+0x3c/0x44) r9:00000000 r8:00000022 r7:00000000 r6:600001d3 r5:c0e6d268 r4:c0e6d268
[<c0465618>] (_raw_spin_lock) from [<c02636cc>] (serial_console_write+0x58/0x134)
r4:c0e6d268
[<c0263674>] (serial_console_write) from [<c0072aec>] (call_console_drivers.constprop.25+0xd0/0xf4)
r10:c0e4e2c8 r9:c0646010 r8:00000022 r7:00000000 r6:c0e4e2dc r5:c0e2d988 r4:c066a2f0
[<c0072a1c>] (call_console_drivers.constprop.25) from [<c00747a4>] (console_unlock+0x370/0x44c)
r9:00000000 r8:00000022 r7:00000006 r6:200001d3 r5:c0e4d908 r4:c0e2e2a4
[<c0074434>] (console_unlock) from [<c00754a4>] (register_console+0x2ac/0x39c)
r10:00000001 r9:00000000 r8:c06502d4 r7:c0e2d988 r6:00000000 r5:c0e2d9b8 r4:c066a2f0
[<c00751f8>] (register_console) from [<c061f150>] (of_setup_earlycon+0x9c/0xb0)
r9:00000080 r8:c0634039 r7:c061f240 r6:00000000 r5:c066a2f0 r4:ffeff000
[<c061f0b4>] (of_setup_earlycon) from [<c0623668>] (setup_of_earlycon+0x100/0x124)
r7:00004288 r6:c063f42c r5:00000000 r4:c0fec000
Fortunately it continues, so I saw the BUG()...
Most drivers seem to fix this by having an early_serial_console_write() that only performs the core functionality of serial_console_write().
Alternatively, (sci-specific) early_console_setup() or (generic) register_earlycon() could call
spin_lock_init(&device->port.lock);
I tried both approaches, and then the kernel doesn't crash anymore. Still, I don't think anything is printed by earlycon: I just see a long delay of a few seconds, presumable until ttySC0 takes over.
Calling serial_console_write() explicitly with a test message makes the kernel lock up. Oops...
Does FIX_EARLYCON_MEM work?
Thanks!
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds