| Message ID | 0ac351b9-46bd-3a35-fab3-73177cabb747@free.fr (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 07/04/17 12:53, Mason wrote: > Hello, > > Some drivers hang or panic before the normal console is available. > In these situations, "earlyprintk" is a life-saver. > > My problem with earlyprintk is that the UART address needs to be > hard-coded in the kernel binary, which means I can't use the same > binary for two chips with different UART addresses, right? > > As far as I understand, "earlycon" helps in that situation, because > it looks up the UART address at run-time in the device tree. > > > QUESTION #1 > > Is that the only difference between earlyprintk and earlycon? > (Probably not, see below) > > > I hacked kernel v4.9.20 to add early console support on my platform. > The patch is provided below, I'd like to hear comments on what needs > fixing... because something is not right. If I call panic() in one of > my driver's probe function, I don't see the output of the panic() > call, which makes the whole exercise rather pointless. > > This is what I see: > > [ 0.000000] Booting Linux on physical CPU 0x0 > [ 0.000000] Linux version 4.9.20-1-rc3 (gcc version 5.3.1 20160113 (Linaro GCC 5.3-2016.02) ) #4 SMP PREEMPT Fri Apr 7 12:57 > [ 0.000000] CPU: ARMv7 Processor [413fc090] revision 0 (ARMv7), cr=10c5387d > [ 0.000000] CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache > [ 0.000000] OF: fdt:Machine model: Sigma Designs SMP8758 Vantage-1172 Rev E1 > [ 0.000000] ENTER param_setup_earlycon > [ 0.000000] ENTER early_init_dt_scan_chosen_stdout > [ 0.000000] early_init_dt_scan_chosen_stdout: scan __earlycon_table > [ 0.000000] name=palmchip compatible=ralink,rt2880-uart setup=early_palmchip_setup > [ 0.000000] ENTER of_setup_earlycon > [ 0.000000] earlycon: palmchip0 at MMIO 0x00010700 (options '115200n8') > [ 0.000000] bootconsole [palmchip0] enabled > [ 0.000000] Memory policy: Data cache writealloc > [ 0.000000] percpu: Embedded 14 pages/cpu @cfdd6000 s24704 r8192 d24448 u57344 > [ 0.000000] Built 1 zonelists in Zone order, mobility grouping on. Total pages: 65024 > [ 0.000000] Kernel command line: mem=256M earlycon > [ 0.000000] PID hash table entries: 1024 (order: 0, 4096 bytes) > [ 0.000000] Dentry cache hash table entries: 32768 (order: 5, 131072 bytes) > [ 0.000000] Inode-cache hash table entries: 16384 (order: 4, 65536 bytes) > [ 0.000000] Memory: 248064K/262144K available (4096K kernel code, 147K rwdata, 892K rodata, 6144K init, 233K bss, 14080K reserved, 0K cma-reserved, 0K highmem) > [ 0.000000] Virtual kernel memory layout: > [ 0.000000] vector : 0xffff0000 - 0xffff1000 ( 4 kB) > [ 0.000000] fixmap : 0xffc00000 - 0xfff00000 (3072 kB) > [ 0.000000] vmalloc : 0xd0800000 - 0xff800000 ( 752 MB) > [ 0.000000] lowmem : 0xc0000000 - 0xd0000000 ( 256 MB) > [ 0.000000] pkmap : 0xbfe00000 - 0xc0000000 ( 2 MB) > [ 0.000000] modules : 0xbf000000 - 0xbfe00000 ( 14 MB) > [ 0.000000] .text : 0xc0008000 - 0xc0500000 (5088 kB) > [ 0.000000] .init : 0xc0600000 - 0xc0c00000 (6144 kB) > [ 0.000000] .data : 0xc0c00000 - 0xc0c24c60 ( 148 kB) > [ 0.000000] .bss : 0xc0c24c60 - 0xc0c5f140 ( 234 kB) > [ 0.000000] Preemptible hierarchical RCU implementation. > [ 0.000000] Build-time adjustment of leaf fanout to 32. > [ 0.000000] RCU restricting CPUs from NR_CPUS=4 to nr_cpu_ids=2. > [ 0.000000] RCU: Adjusting geometry for rcu_fanout_leaf=32, nr_cpu_ids=2 > [ 0.000000] NR_IRQS:16 nr_irqs:16 16 > [ 0.000000] L2C-310 enabling early BRESP for Cortex-A9 > [ 0.000000] L2C-310 ID prefetch enabled, offset 4 lines > [ 0.000000] L2C-310 dynamic clock gating enabled, standby mode enabled > [ 0.000000] L2C-310 cache controller enabled, 8 ways, 512 kB > [ 0.000000] L2C-310: CACHE_ID 0x410000c8, AUX_CTRL 0x72860401 > [ 0.000000] clocksource: tango-xtal: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 70787423951 ns > [ 0.000003] sched_clock: 32 bits at 27MHz, resolution 37ns, wraps every 79536431085ns > [ 0.007873] Switching to timer-based delay loop, resolution 37ns > [ 0.014146] Console: colour dummy device 80x30 > [ 0.018616] console [tty0] enabled > [ 0.022039] bootconsole [palmchip0] disabled > > And it just hangs there... > > If I remove the panic() call, it boots normally, like this: > > ... > [ 0.014147] Console: colour dummy device 80x30 > [ 0.018616] console [tty0] enabled > [ 0.022039] bootconsole [palmchip0] disabled > [ 0.026345] Calibrating delay loop (skipped), value calculated using timer frequency.. 54.25 BogoMIPS (lpj=90000) > [ 0.026364] pid_max: default: 32768 minimum: 301 > ... > > Did I implement something wrong? > Why am I not seeing the output of the panic() call, like I do > with earlyprintk? > Since tty0 is enabled, why isn't it picking up where palmchip0 > left off? As far as I'm aware, tty0 is a purely virtual console: look further down still and you'll probably see a second switch over from tty0 to ttyS0, which will be when the buffered output *actually* starts coming out again. That's certainly what happens for me, albeit with "pl11"->"tty0"->"ttyAMA0", (and complete with not realising ttyAMA0 is still the same port and reprinting the entire log buffer from the top). I believe this is something to do with how the DT stdout-path property is implemented, because with an explicit "console=ttyAMA0" (or ttyS0 in your case) on the command line instead of relying on stdout-path, the boot console does switch directly to the real UART without the intermediate tty0 blind spot. Robin. > > > Earlier discussion: > https://www.spinics.net/lists/linux-serial/msg16227.html > > > This is the patch I'm using: > > diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c > index 85a12f032402..2adabe788c17 100644 > --- a/drivers/tty/serial/8250/8250_early.c > +++ b/drivers/tty/serial/8250/8250_early.c > @@ -172,3 +172,52 @@ static int __init early_omap8250_setup(struct earlycon_device *device, > OF_EARLYCON_DECLARE(omap8250, "ti,omap4-uart", early_omap8250_setup); > > #endif > + > +#ifdef CONFIG_SERIAL_8250_RT288X > + > +extern unsigned int au_serial_in(struct uart_port *p, int offset); > +extern void au_serial_out(struct uart_port *p, int offset, int value); > + > +/*** Copy serial_putc with s/serial8250_early/au_serial/g ***/ > + > +static void __init palmchip_putc(struct uart_port *port, int c) > +{ > + unsigned int status; > + > + au_serial_out(port, UART_TX, c); > + > + for (;;) { > + status = au_serial_in(port, UART_LSR); > + if ((status & BOTH_EMPTY) == BOTH_EMPTY) > + break; > + cpu_relax(); > + } > +} > + > +/*** Copy early_serial8250_write with s/serial_putc/palmchip_putc/g ***/ > + > +static void __init early_palmchip_write(struct console *console, > + const char *s, unsigned int count) > +{ > + struct earlycon_device *device = console->data; > + struct uart_port *port = &device->port; > + > + //extern void printascii(const char *); printascii("EARLY: "); > + uart_console_write(port, s, count, palmchip_putc); > +} > + > +static int __init early_palmchip_setup(struct earlycon_device *device, > + const char *options) > +{ > + struct uart_port *port = &device->port; > + > + if (!(device->port.membase || device->port.iobase)) > + return -ENODEV; > + > + port->regshift = 2; /* Hard coding the value doesn't feel right */ > + device->con->write = early_palmchip_write; > + return 0; > +} > +OF_EARLYCON_DECLARE(palmchip, "ralink,rt2880-uart", early_palmchip_setup); > + > +#endif > diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c > index 080d5a59d0a7..7eb60146cb3f 100644 > --- a/drivers/tty/serial/8250/8250_port.c > +++ b/drivers/tty/serial/8250/8250_port.c > @@ -313,7 +313,7 @@ static void default_serial_dl_write(struct uart_8250_port *up, int value) > -1, /* UART_SCR (unmapped) */ > }; > > -static unsigned int au_serial_in(struct uart_port *p, int offset) > +/*static*/ unsigned int au_serial_in(struct uart_port *p, int offset) > { > if (offset >= ARRAY_SIZE(au_io_in_map)) > return UINT_MAX; > @@ -323,7 +323,7 @@ static unsigned int au_serial_in(struct uart_port *p, int offset) > return __raw_readl(p->membase + (offset << p->regshift)); > } > > -static void au_serial_out(struct uart_port *p, int offset, int value) > +/*static*/ void au_serial_out(struct uart_port *p, int offset, int value) > { > if (offset >= ARRAY_SIZE(au_io_out_map)) > return; > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >
Thanks for answering so quickly! :-) On 07/04/2017 14:18, Robin Murphy wrote: > On 07/04/17 12:53, Mason wrote: > >> Did I implement something wrong? >> Why am I not seeing the output of the panic() call, like I do >> with earlyprintk? >> Since tty0 is enabled, why isn't it picking up where palmchip0 >> left off? > > As far as I'm aware, tty0 is a purely virtual console: look further down > still and you'll probably see a second switch over from tty0 to ttyS0, > which will be when the buffered output *actually* starts coming out > again. That's certainly what happens for me, albeit with > "pl11"->"tty0"->"ttyAMA0", (and complete with not realising ttyAMA0 is > still the same port and reprinting the entire log buffer from the top). Right you are! Also, I had not noticed the "print the entire log buffer from the top" issue you mention. [ 0.000000] Booting Linux on physical CPU 0x0 ... [ 0.000000] earlycon: palmchip0 at MMIO 0x00010700 (options '115200n8') [ 0.000000] bootconsole [palmchip0] enabled ... [ 0.014147] Console: colour dummy device 80x30 [ 0.018616] console [tty0] enabled [ 0.022039] bootconsole [palmchip0] disabled [ 0.000000] Booting Linux on physical CPU 0x0 ... [ 0.000000] earlycon: palmchip0 at MMIO 0x00010700 (options '115200n8') [ 0.000000] bootconsole [palmchip0] enabled [ 0.014147] Console: colour dummy device 80x30 [ 0.018616] console [tty0] enabled [ 0.022039] bootconsole [palmchip0] disabled ... [ 0.460630] Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled [ 0.462278] 10700.serial: ttyS0 at MMIO 0x10700 (irq = 20, base_baud = 460800) is a Palmchip BK-3103 [ 1.084227] console [ttyS0] enabled > I believe this is something to do with how the DT stdout-path property > is implemented, because with an explicit "console=ttyAMA0" (or ttyS0 in > your case) on the command line instead of relying on stdout-path, the > boot console does switch directly to the real UART without the > intermediate tty0 blind spot. Indeed, an explicit console=ttyS0,115200 does avoid the "dupe the entire log" issue. There is still some "stuttering" involved: [ 0.000000] earlycon: palmchip0 at MMIO 0x00010700 (options '115200n8') [ 0.000000] bootconsole [palmchip0] enabled ... [ 0.745811] Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled [ 0.753681] console [ttyS0] disabled [ 0.757426] 10700.serial: ttyS0 at MMIO 0x10700 (irq = 20, base_baud = 460800) is a Palmchip BK-3103 [ 0.766672] console [ttyS0] enabled [ 0.766672] console [ttyS0] enabled [ 0.773726] bootconsole [palmchip0] disabled [ 0.773726] bootconsole [palmchip0] disabled More importantly, it also solves the "hang before panic message" issue: ... [ 0.575937] io scheduler noop registered [ 0.579888] io scheduler deadline registered [ 0.584245] io scheduler cfq registered (default) [ 0.589650] Kernel panic - not syncing: THIS IS A TEST Hopefully, supporting earlycon on this platform can be included in time for v4.12 :-) Greg, Peter, what do you think? ;-) Regards.
diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c index 85a12f032402..2adabe788c17 100644 --- a/drivers/tty/serial/8250/8250_early.c +++ b/drivers/tty/serial/8250/8250_early.c @@ -172,3 +172,52 @@ static int __init early_omap8250_setup(struct earlycon_device *device, OF_EARLYCON_DECLARE(omap8250, "ti,omap4-uart", early_omap8250_setup); #endif + +#ifdef CONFIG_SERIAL_8250_RT288X + +extern unsigned int au_serial_in(struct uart_port *p, int offset); +extern void au_serial_out(struct uart_port *p, int offset, int value); + +/*** Copy serial_putc with s/serial8250_early/au_serial/g ***/ + +static void __init palmchip_putc(struct uart_port *port, int c) +{ + unsigned int status; + + au_serial_out(port, UART_TX, c); + + for (;;) { + status = au_serial_in(port, UART_LSR); + if ((status & BOTH_EMPTY) == BOTH_EMPTY) + break; + cpu_relax(); + } +} + +/*** Copy early_serial8250_write with s/serial_putc/palmchip_putc/g ***/ + +static void __init early_palmchip_write(struct console *console, + const char *s, unsigned int count) +{ + struct earlycon_device *device = console->data; + struct uart_port *port = &device->port; + + //extern void printascii(const char *); printascii("EARLY: "); + uart_console_write(port, s, count, palmchip_putc); +} + +static int __init early_palmchip_setup(struct earlycon_device *device, + const char *options) +{ + struct uart_port *port = &device->port; + + if (!(device->port.membase || device->port.iobase)) + return -ENODEV; + + port->regshift = 2; /* Hard coding the value doesn't feel right */ + device->con->write = early_palmchip_write; + return 0; +} +OF_EARLYCON_DECLARE(palmchip, "ralink,rt2880-uart", early_palmchip_setup); + +#endif diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 080d5a59d0a7..7eb60146cb3f 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -313,7 +313,7 @@ static void default_serial_dl_write(struct uart_8250_port *up, int value) -1, /* UART_SCR (unmapped) */ }; -static unsigned int au_serial_in(struct uart_port *p, int offset) +/*static*/ unsigned int au_serial_in(struct uart_port *p, int offset) { if (offset >= ARRAY_SIZE(au_io_in_map)) return UINT_MAX; @@ -323,7 +323,7 @@ static unsigned int au_serial_in(struct uart_port *p, int offset) return __raw_readl(p->membase + (offset << p->regshift)); } -static void au_serial_out(struct uart_port *p, int offset, int value) +/*static*/ void au_serial_out(struct uart_port *p, int offset, int value) { if (offset >= ARRAY_SIZE(au_io_out_map)) return;