Hi Paul,
2010/10/5 Paul Walmsley <paul@xxxxxxxxx>:
> Hello Lei,
>
> On Tue, 5 Oct 2010, Ming Lei wrote:
>
>> 2010/10/5 Kevin Hilman <khilman@xxxxxxxxxxxxxxxxxxx>:
>> > Ming Lei <tom.leiming@xxxxxxxxx> writes:
>> >
>> >> 2010/10/4 Kevin Hilman <khilman@xxxxxxxxxxxxxxxxxxx>:
>> >>>
>> >>> Why? What do you need from the PM branch that is not in l-o master?
>> >>
>> >> Seems master branch works fine for me, my beagle board doesn't hang
>> >> uart3 disabling clocks.
>> >
>> > Master branch and PM branch have exactly the same functionality for
>> > UART hwmods. The problem was that you manually enabled DEBUG in
>> > omap_hwmod.c.
>>
>> Yes, you are correct. If DEBUG in omap_hwmod.c is enabled manually,
>> and pass the parameter of 'earlyprintk loglevel=8' to kernel from bootloader,
>> this issue can be triggered even with master branch.
>
> Does this experimental patch solve the problem, even if DEBUG is enabled
> in the hwmod code?
>
>
> - Paul
>
> From d928bd31c9c4ad16a044b244ef3d2ad3ed648f6f Mon Sep 17 00:00:00 2001
> From: Paul Walmsley <paul@xxxxxxxxx>
> Date: Tue, 5 Oct 2010 00:11:27 -0600
> Subject: [PATCH] RFC: omap serial: block console output while resetting earlyconsole UART
>
> Currently, no attempt is made to block console output while the
> earlyconsole UART is unavailable. This can result in silent crashes
> that are very difficult to debug due to the lack of console output.
> This patch holds the console semaphore while resetting the active console
> UART, which causes all console output during that time to be buffered and
> then transmitted after the console semaphore is released.
Good works, this patch does fix the issue!
With the patch, even DEBUG in omap_hwmod.c is enabled manually
and 'earlyprintk loglevel=8' is passed to kernel, my beagle board can't
hang after 'uart3: disabling clocks' is printed.
>
> Not-yet-signed-off-by: Paul Walmsley <paul@xxxxxxxxx>
> ---
> arch/arm/mach-omap2/serial.c | 100 ++++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 100 insertions(+), 0 deletions(-)
>
> diff --git a/arch/arm/mach-omap2/serial.c b/arch/arm/mach-omap2/serial.c
> index 338e46a..577f8f9 100644
> --- a/arch/arm/mach-omap2/serial.c
> +++ b/arch/arm/mach-omap2/serial.c
> @@ -28,10 +28,13 @@
> #include <linux/serial_8250.h>
> #include <linux/pm_runtime.h>
>
> +#include <linux/console.h>
> +
> #ifdef CONFIG_SERIAL_OMAP
> #include <plat/omap-serial.h>
> #endif
>
> +#include <plat/serial.h>
> #include <plat/common.h>
> #include <plat/board.h>
> #include <plat/clock.h>
> @@ -39,6 +42,8 @@
> #include <plat/omap_hwmod.h>
> #include <plat/omap_device.h>
>
> +#include <asm/memory.h>
> +
> #include "prm.h"
> #include "pm.h"
> #include "cm.h"
> @@ -51,6 +56,8 @@
> #define UART_ERRATA_FIFO_FULL_ABORT (0x1 << 0)
> #define UART_ERRATA_i202_MDR1_ACCESS (0x1 << 1)
>
> +#define uart_id_to_ttys_id(u) (u - 1)
> +
> /*
> * NOTE: By default the serial timeout is disabled as it causes lost characters
> * over the serial ports. This means that the UART clocks will stay on until
> @@ -106,6 +113,83 @@ static LIST_HEAD(uart_list);
> static u8 num_uarts;
>
> /*
> + * early_console_uart: if earlyconsole is enabled and active, the UART
> + * ID (e.g., 1, 2, 3, 4) will be stored here. '0' means earlyconsole
> + * is disabled or some problem occurred during earlyconsole handling.
> + */
> +static int early_console_uart;
> +
> +#define for_each_console(con) \
> + for (con = console_drivers; con != NULL; con = con->next)
> +
> +/* XXX belongs in kernel/printk.c or some earlyconsole file */
> +/* XXX The "earlycon" string is an ugly hack */
> +int _is_early_console_enabled(void)
> +{
> + int ret = 0;
> + struct console *c;
> +
> + acquire_console_sem();
> + for_each_console(c)
> + if (!strcmp("earlycon", c->name))
> + ret = 1;
> + release_console_sem();
> +
> + return ret;
> +}
> +
> +/* XXX document */
> +static int _get_early_console_uart(void)
> +{
> + u32 v;
> + int u = -EINVAL;
> +
> + v = __raw_readl(phys_to_virt(OMAP_UART_INFO));
> + /* XXX see the OMAP debug-macro.S for this table */
> + switch (v) {
> + case 0:
> + case OMAP2UART1:
> + u = 1;
> + break;
> + case OMAP2UART2:
> + u = 2;
> + break;
> + case OMAP2UART3:
> + case OMAP3UART3:
> + case OMAP4UART3:
> + u = 3;
> + break;
> + case OMAP3UART4:
> + case OMAP4UART4:
> + u = 4;
> + break;
> + case ZOOM_UART:
> + WARN(1, "omap serial: ZOOM UART in use - does that go through "
> + "the OMAP serial code?\n");
> + break;
> + default:
> + WARN(1, "omap serial: unknown serial port in use!\n");
> + }
> +
> + return u;
> +}
> +
> +/* XXX document */
> +static void _store_early_console_uart_id(void)
> +{
> + int uart_id;
> +
> + if (_is_early_console_enabled()) {
> + uart_id = _get_early_console_uart();
> + if (uart_id > 0) {
> + early_console_uart = uart_id;
> + pr_info("omap serial: early console active on UART%d (ttyS%d)\n",
> + uart_id, uart_id_to_ttys_id(uart_id));
> + }
> + }
> +}
> +
> +/*
> * Since these idle/enable hooks are used in the idle path itself
> * which has interrupts disabled, use the non-locking versions of
> * the hwmod enable/disable functions.
> @@ -801,6 +885,17 @@ void __init omap_serial_init_port(int port)
> oh->dev_attr = uart;
>
> /*
> + * XXX How do we know whether the console is on this UART or not?
> + * We should only call acquire_console_sem() if the console is on
> + * this UART.
> + *
> + * Of course, the console is not the only thing that could be using
> + * this UART.
> + */
> + if (uart->num == uart_id_to_ttys_id(early_console_uart))
> + acquire_console_sem();
> +
> + /*
> * Because of early UART probing, UART did not get idled
> * on init. Now that omap_device is ready, ensure full idle
> * before doing omap_device_enable().
> @@ -824,6 +919,9 @@ void __init omap_serial_init_port(int port)
> omap_uart_block_sleep(uart);
> uart->timeout = DEFAULT_TIMEOUT;
>
> + if (uart->num == uart_id_to_ttys_id(early_console_uart))
> + release_console_sem();
> +
> if ((cpu_is_omap34xx() && uart->padconf) ||
> (uart->wk_en && uart->wk_mask)) {
> device_init_wakeup(&od->pdev.dev, true);
> @@ -846,6 +944,8 @@ void __init omap_serial_init(void)
> {
> struct omap_uart_state *uart;
>
> + _store_early_console_uart_id();
> +
> list_for_each_entry(uart, &uart_list, node)
> omap_serial_init_port(uart->num);
> }
> --
> 1.7.1
>
thanks,
--
Lei Ming
--
To unsubscribe from this list: send the line "unsubscribe linux-omap" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
