Add board_pre_console_putc to deal with early console output

This patch adds support for console output before the console is inited. The main purpose of this is to deal with a very early panic() which would otherwise cause a silent hang.

A new board_pre_console_putc() function is added to the board API. If provided by the board it will be called in the event of console output before the console is ready. This function should turn on all UARTs and spray the character out if it possibly can.

The feature is controlled by a new CONFIG_PRE_CONSOLE_PUTC option.

Signed-off-by Simon Glass <[email protected]>

---

common/console.c +2 -1

index f17875e..d79bcf4 100644
@@ -329,14 +329,30 @@ int tstc(void)
       return serial_tstc();
 }
 
-#ifdef CONFIG_PRE_CONSOLE_BUFFER
+#ifdef CONFIG_PRE_CONSOLE_PUTC
+/* Provide a default function for when no console is available */

Hi Simon,

Quoted 13 lines · Simon Glass

This patch adds support for console output before the console is inited. The main purpose of this is to deal with a very early panic() which would otherwise cause a silent hang.

A new board_pre_console_putc() function is added to the board API. If provided by the board it will be called in the event of console output before the console is ready. This function should turn on all UARTs and spray the character out if it possibly can.

The feature is controlled by a new CONFIG_PRE_CONSOLE_PUTC option.

Signed-off-by Simon Glass <[email protected]>

---

[snip]

Quoted 18 lines

common/console.c +9 -1

index f17875e..d79bcf4 100644
@@ -329,14 +329,30 @@ int tstc(void)
 ? ? ? ?return serial_tstc();
 ?}
 
-#ifdef CONFIG_PRE_CONSOLE_BUFFER
+#ifdef CONFIG_PRE_CONSOLE_PUTC
+/* Provide a default function for when no console is available */
+static void __board_pre_console_putc(int ch)
+{
+ ? ? ? /* Just return since we can't access the console */
+}
+
+void board_pre_console_putc(const char *msg) __attribute__((weak,
+ ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? alias("__board_pre_console_putc")));

common/console.c int tstc(void) · line 343

Quoted 3 lines

common/console.c +3 -0

+#endif
+
+#if defined(CONFIG_PRE_CONSOLE_BUFFER) || defined(CONFIG_PRE_CONSOLE_PUTC)

I don't think we need this - If CONFIG_PRE_CONSOLE_PUTC then board_pre_console_putc() must also be defined - I would prefer a compilation due to undefined function that head-scratching as to why th output I expected did not occur

[snip]

Regards,

Graeme

This patch adds support for console output before the console is inited. The main purpose of this is to deal with a very early panic() which would otherwise cause a silent hang.

A new board_pre_console_putc() function is added to the board API. If provided by the board it will be called in the event of console output before the console is ready. This function should turn on all UARTs and spray the character out if it possibly can.

The feature is controlled by a new CONFIG_PRE_CONSOLE_PUTC option.

Signed-off-by Simon Glass <[email protected]>

Hi Simon,

Quoted 9 lines · Simon Glass

This patch adds support for console output before the console is inited. The main purpose of this is to deal with a very early panic() which would otherwise cause a silent hang.

A new board_pre_console_putc() function is added to the board API. If provided by the board it will be called in the event of console output before the console is ready. This function should turn on all UARTs and spray the character out if it possibly can.

Quoted 3 lines

The feature is controlled by a new CONFIG_PRE_CONSOLE_PUTC option.

Signed-off-by Simon Glass <[email protected]>

Acked-by Graeme Russ <[email protected]>

Hi,

Quoted 2 lines · Graeme Russ

Hi Simon,

Quoted 5 lines

Quoted 5 lines

A new board_pre_console_putc() function is added to the board API. If provided by the board it will be called in the event of console output before the console is ready. This function should turn on all UARTs and spray the character out if it possibly can.

Quoted 6 lines

Quoted 3 lines

The feature is controlled by a new CONFIG_PRE_CONSOLE_PUTC option.

Signed-off-by Simon Glass <[email protected]>

Acked-by Graeme Russ <[email protected]>

Just going through my backlog. Any interest in merging this?

Quoted 5 lines · Simon Glass

Hi,

Quoted 2 lines · Graeme Russ

Hi Simon,

Hi Simon,

Quoted 9 lines

Quoted 9 lines

Quoted 8 lines

A new board_pre_console_putc() function is added to the board API. If provided by the board it will be called in the event of console output before the console is ready. This function should turn on all UARTs and spray the character out if it possibly can.

The feature is controlled by a new CONFIG_PRE_CONSOLE_PUTC option.

Signed-off-by Simon Glass <[email protected]>

Quoted 3 lines

Quoted 2 lines

Acked-by Graeme Russ <[email protected]>

Just going through my backlog. Any interest in merging this?

I have frankly missed the patch - I will read the related thread, and I will take a look. For now I will put this patch in my TODO list in patchwork.

Best regards,
Stefano

--
=====================================================================
DENX Software Engineering GmbH, ? ? MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: +49-8142-66989-0 Fax: +49-8142-66989-80 ?Email: office at denx.de
=====================================================================

This patch adds support for console output before the console is inited. The main purpose of this is to deal with a very early panic() which would otherwise cause a silent hang.

A new board_pre_console_putc() function is added to the board API. If provided by the board it will be called in the event of console output before the console is ready. This function should turn on all UARTs and spray the character out if it possibly can.

The feature is controlled by a new CONFIG_PRE_CONSOLE_PUTC option.

Signed-off-by Simon Glass <[email protected]>

---

Changes in v2:
- Made this feature conditional on CONFIG_PRE_CONSOLE_PANIC

Changes in v3:
- Rewrite this to be independent of panic()
- Rename feature to CONFIG_PRE_CONSOLE_PUTC

Changes in v4:
- Remove weak function, so we get a link error if it is undefined by the board

Quoted 9 lines · Simon Glass

This patch adds support for console output before the console is inited. The main purpose of this is to deal with a very early panic() which would otherwise cause a silent hang.

A new board_pre_console_putc() function is added to the board API. If provided by the board it will be called in the event of console output before the console is ready. This function should turn on all UARTs and spray the character out if it possibly can.

Quoted 4 lines

The feature is controlled by a new CONFIG_PRE_CONSOLE_PUTC option.

Signed-off-by Simon Glass <[email protected]>

---

Hi Simon,

Quoted 9 lines

Changes in v2:
- Made this feature conditional on CONFIG_PRE_CONSOLE_PANIC

Changes in v3:
- Rewrite this to be independent of panic()
- Rename feature to CONFIG_PRE_CONSOLE_PUTC

Changes in v4:
- Remove weak function, so we get a link error if it is undefined by the board

maybe I have not understood the real goal of this patch. We have already a CONFIG_PRE_CONSOLE_BUFFER, that tries to store the output when the console is not avalable - and can be retrieved with a JTAG debugger.

Your patch adds a way to call some serial setup in board code, but it is not said that works or can work for all / most boards. Compared to the usage of the circular buffer, it is not so general - am I missing something ?

Best regards,
Stefano Babic

--
=====================================================================
DENX Software Engineering GmbH, ? ? MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: +49-8142-66989-0 Fax: +49-8142-66989-80 ?Email: office at denx.de
=====================================================================

It actually started as a last-ditch panic message printer. It morphed into the general pre-console putc after discussions on the list (with Graeme).

It can happen that your early board code does not know what clocks to use, or can't find a console, or some other critical error. It then calls panic() which silently dies or maybe reboots if you are lucky. This problem mostly comes about with device trees, where we must have certain info in the device tree before we can even get to relocation.

The idea is that boards provide a way of outputting characters which tries to work on all types of boards with that SOC. For example, they output the characters on all UARTs with various clock options, etc.

We use it on Tegra to print a friendly panic message when something is horribly wrong. In this case we will never make it to relocation so the pre-console buffer will not be displayed. So we can't rely on that.

Quoted 10 lines · Simon Glass

It actually started as a last-ditch panic message printer. It morphed into the general pre-console putc after discussions on the list (with Graeme).

It can happen that your early board code does not know what clocks to use, or can't find a console, or some other critical error. It then calls panic() which silently dies or maybe reboots if you are lucky. This problem mostly comes about with device trees, where we must have certain info in the device tree before we can even get to relocation.

Quoted 8 lines

The idea is that boards provide a way of outputting characters which tries to work on all types of boards with that SOC. For example, they output the characters on all UARTs with various clock options, etc.

We use it on Tegra to print a friendly panic message when something is horribly wrong. In this case we will never make it to relocation so the pre-console buffer will not be displayed. So we can't rely on that.

I do not know if this mechanism can be used on other SOCs, but IMHO it does not hurt and it helps at least on Tegra, as you explained me.

Applied to u-boot-staging, sbabic at denx.de branch

Best regards,
Stefano Babic

--
=====================================================================
DENX Software Engineering GmbH, ? ? MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: +49-8142-66989-0 Fax: +49-8142-66989-80 ?Email: office at denx.de
=====================================================================

Hi Stefan,

Quoted 21 lines · Stefano Babic

Quoted 18 lines · Simon Glass

It actually started as a last-ditch panic message printer. It morphed into the general pre-console putc after discussions on the list (with Graeme).

It can happen that your early board code does not know what clocks to use, or can't find a console, or some other critical error. It then calls panic() which silently dies or maybe reboots if you are lucky. This problem mostly comes about with device trees, where we must have certain info in the device tree before we can even get to relocation.

The idea is that boards provide a way of outputting characters which tries to work on all types of boards with that SOC. For example, they output the characters on all UARTs with various clock options, etc.

We use it on Tegra to print a friendly panic message when something is horribly wrong. In this case we will never make it to relocation so the pre-console buffer will not be displayed. So we can't rely on that.

Quoted 4 lines

I do not know if this mechanism can be used on other SOCs, but IMHO it does not hurt and it helps at least on Tegra, as you explained me.

Applied to u-boot-staging, sbabic at denx.de branch

Thanks. I think it can be used on any SOC with internal UARTs and a reasonably small list of permitted clock speeds. I suspect I will be trying it out on a few before long.

Hi Simon,

Quoted 29 lines · Simon Glass

Hi Stefan,

Quoted 25 lines · Stefano Babic

Quoted 10 lines · Simon Glass

It actually started as a last-ditch panic message printer. It morphed into the general pre-console putc after discussions on the list (with Graeme).

It can happen that your early board code does not know what clocks to use, or can't find a console, or some other critical error. It then calls panic() which silently dies or maybe reboots if you are lucky. This problem mostly comes about with device trees, where we must have certain info in the device tree before we can even get to relocation.

Quoted 8 lines

The idea is that boards provide a way of outputting characters which tries to work on all types of boards with that SOC. For example, they output the characters on all UARTs with various clock options, etc.

We use it on Tegra to print a friendly panic message when something is horribly wrong. In this case we will never make it to relocation so the pre-console buffer will not be displayed. So we can't rely on that.

I do not know if this mechanism can be used on other SOCs, but IMHO it does not hurt and it helps at least on Tegra, as you explained me.

Applied to u-boot-staging, sbabic at denx.de branch

Quoted 3 lines

Thanks. I think it can be used on any SOC with internal UARTs and a reasonably small list of permitted clock speeds. I suspect I will be trying it out on a few before long.

Can it be used in conjuction with PRE_CONSOLE_BUFFER? i.e. panic() prints the contents of the PRE_CONSOLE_BUFFER before the panic message? I think that would be invaluable in determining what was happening leading up to the panic

Regards,

Graeme

Hi Graeme,

Quoted 36 lines · Graeme Russ

Hi Simon,

Quoted 32 lines · Simon Glass

Hi Stefan,

Quoted 21 lines · Stefano Babic

Quoted 10 lines · Simon Glass

It actually started as a last-ditch panic message printer. It morphed into the general pre-console putc after discussions on the list (with Graeme).

It can happen that your early board code does not know what clocks to use, or can't find a console, or some other critical error. It then calls panic() which silently dies or maybe reboots if you are lucky. This problem mostly comes about with device trees, where we must have certain info in the device tree before we can even get to relocation.

Quoted 8 lines

The idea is that boards provide a way of outputting characters which tries to work on all types of boards with that SOC. For example, they output the characters on all UARTs with various clock options, etc.

We use it on Tegra to print a friendly panic message when something is horribly wrong. In this case we will never make it to relocation so the pre-console buffer will not be displayed. So we can't rely on that.

Quoted 4 lines

I do not know if this mechanism can be used on other SOCs, but IMHO it does not hurt and it helps at least on Tegra, as you explained me.

Applied to u-boot-staging, sbabic at denx.de branch

Thanks. I think it can be used on any SOC with internal UARTs and a reasonably small list of permitted clock speeds. I suspect I will be trying it out on a few before long.

Quoted 4 lines

Can it be used in conjuction with PRE_CONSOLE_BUFFER? i.e. panic() prints the contents of the PRE_CONSOLE_BUFFER before the panic message? I think that would be invaluable in determining what was happening leading up to the panic

It could have been when it was still a pre-console panic. But now that it has morphed into a general putc(), I suppose the only option is to somehow detect the first call and send the pre-console text first?

Hi Simon,

Quoted 39 lines · Simon Glass

Hi Graeme,

Quoted 36 lines · Graeme Russ

Hi Simon,

Quoted 32 lines · Simon Glass

Hi Stefan,

Quoted 21 lines · Stefano Babic

Quoted 10 lines · Simon Glass

It actually started as a last-ditch panic message printer. It morphed into the general pre-console putc after discussions on the list (with Graeme).

It can happen that your early board code does not know what clocks to use, or can't find a console, or some other critical error. It then calls panic() which silently dies or maybe reboots if you are lucky. This problem mostly comes about with device trees, where we must have certain info in the device tree before we can even get to relocation.

Quoted 8 lines

The idea is that boards provide a way of outputting characters which tries to work on all types of boards with that SOC. For example, they output the characters on all UARTs with various clock options, etc.

We use it on Tegra to print a friendly panic message when something is horribly wrong. In this case we will never make it to relocation so the pre-console buffer will not be displayed. So we can't rely on that.

Quoted 4 lines

I do not know if this mechanism can be used on other SOCs, but IMHO it does not hurt and it helps at least on Tegra, as you explained me.

Applied to u-boot-staging, sbabic at denx.de branch

Thanks. I think it can be used on any SOC with internal UARTs and a reasonably small list of permitted clock speeds. I suspect I will be trying it out on a few before long.

Quoted 8 lines

Quoted 4 lines

Can it be used in conjuction with PRE_CONSOLE_BUFFER? i.e. panic() prints the contents of the PRE_CONSOLE_BUFFER before the panic message? I think that would be invaluable in determining what was happening leading up to the panic

It could have been when it was still a pre-console panic. But now that it has morphed into a general putc(), I suppose the only option is to somehow detect the first call and send the pre-console text first?

Couldn't the panic() function detect that the pre console buffer is not empty and dump it before the panic message? Maybe even a generic panic_dump_pre_console_buffer() which checks if console has been initialised (in which case the buffer has already been dumped) and if the buffer is not empty, use pre_console_putc() to dump the buffer. This would be the first call in panic() followed by printing the panic message

Regards,

Graeme