linux-kernel - Re: [PATCH] drivers/cros

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Message-ID: <CA+Dqm30XF=wDVcdUabbHySp-fwf+zFNqXpdYDW3bDTOwRbkiZw@mail.gmail.com>
Date:   Wed, 21 Dec 2022 16:55:02 -0700
From:   Rob Barnes <robbarnes@...gle.com>
To:     Prashant Malani <pmalani@...omium.org>
Cc:     Guenter Roeck <groeck@...omium.org>,
        chrome-platform@...ts.linux.dev, linux-kernel@...r.kernel.org,
        dtor@...omium.org, Benson Leung <bleung@...omium.org>
Subject: Re: [PATCH] drivers/cros_ec: Handle CrOS EC panics

On Wed, Dec 21, 2022 at 12:23 PM Prashant Malani <pmalani@...omium.org> wrote:
>
> Hi Rob,
>
> I'd suggest using the commit title tag "platform/chrome: cros_ec: ..."
> for commits which are "ChromeOS EC" wide. That's in line with
> other recent commits in this directory.

Ack. Will do.

>
> On Wed, Dec 21, 2022 at 10:56 AM Rob Barnes <robbarnes@...gle.com> wrote:
> >
> > Add handler for CrOS EC panic events. When a panic is reported,
> > poll EC log then force an orderly shutdown.
> >
> > This will preserve the EC log leading up to the crash.
> >
> > Signed-off-by: Rob Barnes <robbarnes@...gle.com>
> > ---
> >  drivers/platform/chrome/cros_ec_debugfs.c   | 24 +++++++++++++++++++++
> >  drivers/platform/chrome/cros_ec_lpc.c       | 10 +++++++++
> >  include/linux/platform_data/cros_ec_proto.h |  9 ++++++++
> >  3 files changed, 43 insertions(+)
> >
> > diff --git a/drivers/platform/chrome/cros_ec_debugfs.c b/drivers/platform/chrome/cros_ec_debugfs.c
> > index 21d973fc6be2..31637a4e4cf9 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 +438,23 @@ 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 +491,12 @@ 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..21958c3b0c28 100644
> > --- a/drivers/platform/chrome/cros_ec_lpc.c
> > +++ b/drivers/platform/chrome/cros_ec_lpc.c
> > @@ -21,6 +21,7 @@
> >  #include <linux/platform_data/cros_ec_proto.h>
> >  #include <linux/platform_device.h>
> >  #include <linux/printk.h>
> > +#include <linux/reboot.h>
> >  #include <linux/suspend.h>
> >
> >  #include "cros_ec.h"
> > @@ -332,6 +333,15 @@ static void cros_ec_lpc_acpi_notify(acpi_handle device, u32 value, void *data)
> >
> >         if (value == ACPI_NOTIFY_DEVICE_WAKE)
> >                 pm_system_wakeup();
> > +
> > +       if (value == ACPI_NOTIFY_CROS_EC_PANIC) {
> > +               dev_err(ec_dev->dev,
> > +                       "CrOS EC Panic Reported. Shutdown is imminent!");
> > +               blocking_notifier_call_chain(&ec_dev->panic_notifier, 0,
> > +                                            ec_dev);
> > +               /* Begin orderly shutdown. Force shutdown after 1 second. */
> > +               hw_protection_shutdown("CrOS EC Panic", 1000);
>
> I feel like this patch is doing 2 things: pulling the logs, and then
> starting a shutdown.
> This should be split into 2 patches.

Ack. Will do.

>
> > +       }
> >  }
>
> Line limits are now 100 chars[1], so most of these lines can fit on 1 line.
>
> >
> >  static int cros_ec_lpc_probe(struct platform_device *pdev)
> > diff --git a/include/linux/platform_data/cros_ec_proto.h b/include/linux/platform_data/cros_ec_proto.h
> > index e43107e0bee1..1c4487271836 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
>
> Can you provide a link (either in the commit, or here in the comment)
> to the coreboot/BIOS code which uses this value? I feel this should
> be documented in some form that correlates the caller and the callee.

Link: https://chromium-review.googlesource.com/c/chromiumos/third_party/coreboot/+/4023535

>
> > +
> >  /*
> >   * 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;
>
> Any reason we cannot use the existing event_notifier (with value argument)?
> It's a system panic, so I doubt that computational overhead for other
> notifier block
> listeners is a concern.

The value field is already being used for "queued_during_suspend" in
event_notifier.
>
> BR,
>
> -Prashant
>
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=bdc48fa11e46f867ea4d75fa59ee87a7f48be144