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Message-ID: <66b4fb4f-35cc-1ebb-1d43-c2f942937670@samsung.com>
Date:   Tue, 10 Jan 2023 23:09:11 +0100
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Subject: Re: [PATCH v3 1/2] platform/chrome: cros_ec: Poll EC log on EC
 panic
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To:     Rob Barnes <robbarnes@google.com>, groeck@chromium.org,
        pmalani@chromium.org
Cc:     chrome-platform@lists.linux.dev, linux-kernel@vger.kernel.org,
        dtor@chromium.org
From:   Marek Szyprowski <m.szyprowski@samsung.com>
In-Reply-To: <20230104011524.369764-2-robbarnes@google.com>
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References: <20230104011524.369764-1-robbarnes@google.com>
        <20230104011524.369764-2-robbarnes@google.com>
        <CGME20230110220912eucas1p250dae7ff73fbc12e79b1149de6279a01@eucas1p2.samsung.com>
Precedence: bulk

Hi Rob,

On 04.01.2023 02:15, Rob Barnes wrote:
> Add handler for CrOS EC panic events. When a panic is reported,
> immediately poll for EC log.
>
> This should result in the log leading to the EC panic being
> preserved.
>
> ACPI_NOTIFY_CROS_EC_PANIC is defined in coreboot at
> https://review.coreboot.org/plugins/gitiles/coreboot/+/refs/heads/master/src/ec/google/chromeec/acpi/ec.asl
>
> Signed-off-by: Rob Barnes <robbarnes@google.com>

This patch landed in today's linux-next as commit d90fa2c64d59 
("platform/chrome: cros_ec: Poll EC log on EC panic"). Unfortunately it 
introduces the following runtime warning on my test systems:

INFO: trying to register non-static key.
The code is fine but needs lockdep annotation, or maybe
you didn't initialize this object before use?
turning off the locking correctness validator.
CPU: 0 PID: 62 Comm: kworker/u16:1 Not tainted 
6.2.0-rc3-next-20230110-00037-g7c2b0426386a #6112
Hardware name: Samsung Exynos (Flattened Device Tree)
Workqueue: events_unbound async_run_entry_fn
  unwind_backtrace from show_stack+0x10/0x14
  show_stack from dump_stack_lvl+0x58/0x70
  dump_stack_lvl from register_lock_class+0x998/0x9a8
  register_lock_class from __lock_acquire+0x6c/0x2a80
  __lock_acquire from lock_acquire+0x124/0x3f0
  lock_acquire from down_write+0x40/0xd8
  down_write from blocking_notifier_chain_register+0x28/0x58
  blocking_notifier_chain_register from cros_ec_debugfs_probe+0x324/0x3b4
  cros_ec_debugfs_probe from platform_probe+0x5c/0xb8
  platform_probe from really_probe+0xe0/0x414
  really_probe from __driver_probe_device+0x9c/0x200
  __driver_probe_device from driver_probe_device+0x30/0xc0
  driver_probe_device from __device_attach_driver+0xa8/0x120
  __device_attach_driver from bus_for_each_drv+0x7c/0xc0
  bus_for_each_drv from __device_attach_async_helper+0xa0/0xf4
  __device_attach_async_helper from async_run_entry_fn+0x40/0x154
  async_run_entry_fn from process_one_work+0x288/0x790
  process_one_work from worker_thread+0x44/0x504
  worker_thread from kthread+0xf0/0x124
  kthread from ret_from_fork+0x14/0x2c
Exception stack(0xf0a6dfb0 to 0xf0a6dff8)
...
------------[ cut here ]------------

That's because the panic_notifier entry is not initialized to the sane 
value. Adding the following line:

BLOCKING_INIT_NOTIFIER_HEAD(&ec_dev->panic_notifier);

to drivers/platform/chrome/cros_ec.c to cros_ec_register() function 
fixes the issue. I will send the incremental fix in a few minutes.

> ---
>
> Changelog since v1:
> - Split into two patches
> - Moved panic handle before mkbp loop
> - Switched to dev_emerg message
>
>   drivers/platform/chrome/cros_ec_debugfs.c   | 23 +++++++++++++++++++++
>   drivers/platform/chrome/cros_ec_lpc.c       |  7 +++++++
>   include/linux/platform_data/cros_ec_proto.h |  9 ++++++++
>   3 files changed, 39 insertions(+)
>
> diff --git a/drivers/platform/chrome/cros_ec_debugfs.c b/drivers/platform/chrome/cros_ec_debugfs.c
> index 21d973fc6be2..34f7b46f8761 100644
> --- a/drivers/platform/chrome/cros_ec_debugfs.c
> +++ b/drivers/platform/chrome/cros_ec_debugfs.c
> @@ -49,6 +49,7 @@ struct cros_ec_debugfs {
>   	struct delayed_work log_poll_work;
>   	/* EC panicinfo */
>   	struct debugfs_blob_wrapper panicinfo_blob;
> +	struct notifier_block notifier_panic;
>   };
>   
>   /*
> @@ -437,6 +438,22 @@ static int cros_ec_create_panicinfo(struct cros_ec_debugfs *debug_info)
>   	return ret;
>   }
>   
> +static int cros_ec_debugfs_panic_event(struct notifier_block *nb,
> +				       unsigned long queued_during_suspend, void *_notify)
> +{
> +	struct cros_ec_debugfs *debug_info =
> +		container_of(nb, struct cros_ec_debugfs, notifier_panic);
> +
> +	if (debug_info->log_buffer.buf) {
> +		/* Force log poll work to run immediately */
> +		mod_delayed_work(debug_info->log_poll_work.wq, &debug_info->log_poll_work, 0);
> +		/* Block until log poll work finishes */
> +		flush_delayed_work(&debug_info->log_poll_work);
> +	}
> +
> +	return NOTIFY_DONE;
> +}
> +
>   static int cros_ec_debugfs_probe(struct platform_device *pd)
>   {
>   	struct cros_ec_dev *ec = dev_get_drvdata(pd->dev.parent);
> @@ -473,6 +490,12 @@ static int cros_ec_debugfs_probe(struct platform_device *pd)
>   	debugfs_create_u16("suspend_timeout_ms", 0664, debug_info->dir,
>   			   &ec->ec_dev->suspend_timeout_ms);
>   
> +	debug_info->notifier_panic.notifier_call = cros_ec_debugfs_panic_event;
> +	ret = blocking_notifier_chain_register(&ec->ec_dev->panic_notifier,
> +					       &debug_info->notifier_panic);
> +	if (ret)
> +		goto remove_debugfs;
> +
>   	ec->debug_info = debug_info;
>   
>   	dev_set_drvdata(&pd->dev, ec);
> diff --git a/drivers/platform/chrome/cros_ec_lpc.c b/drivers/platform/chrome/cros_ec_lpc.c
> index 7fc8f82280ac..5738f1d25091 100644
> --- a/drivers/platform/chrome/cros_ec_lpc.c
> +++ b/drivers/platform/chrome/cros_ec_lpc.c
> @@ -320,6 +320,13 @@ static void cros_ec_lpc_acpi_notify(acpi_handle device, u32 value, void *data)
>   
>   	ec_dev->last_event_time = cros_ec_get_time_ns();
>   
> +	if (value == ACPI_NOTIFY_CROS_EC_PANIC) {
> +		dev_emerg(ec_dev->dev, "CrOS EC Panic Reported. Shutdown is imminent!");
> +		blocking_notifier_call_chain(&ec_dev->panic_notifier, 0, ec_dev);
> +		/* Do not query for other events after a panic is reported */
> +		return;
> +	}
> +
>   	if (ec_dev->mkbp_event_supported)
>   		do {
>   			ret = cros_ec_get_next_event(ec_dev, NULL,
> diff --git a/include/linux/platform_data/cros_ec_proto.h b/include/linux/platform_data/cros_ec_proto.h
> index e43107e0bee1..7fb2196f99b0 100644
> --- a/include/linux/platform_data/cros_ec_proto.h
> +++ b/include/linux/platform_data/cros_ec_proto.h
> @@ -41,6 +41,13 @@
>   #define EC_MAX_REQUEST_OVERHEAD		1
>   #define EC_MAX_RESPONSE_OVERHEAD	32
>   
> +/*
> + * EC panic is not covered by the standard (0-F) ACPI notify values.
> + * Arbitrarily choosing B0 to notify ec panic, which is in the 84-BF
> + * device specific ACPI notify range.
> + */
> +#define ACPI_NOTIFY_CROS_EC_PANIC 0xB0
> +
>   /*
>    * Command interface between EC and AP, for LPC, I2C and SPI interfaces.
>    */
> @@ -176,6 +183,8 @@ struct cros_ec_device {
>   	/* The platform devices used by the mfd driver */
>   	struct platform_device *ec;
>   	struct platform_device *pd;
> +
> +	struct blocking_notifier_head panic_notifier;
>   };
>   
>   /**

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland