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SubjectRe: [PATCH 2/2] pm_trace: Add sysfs attr for rechecking dev hash.
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On Sunday, October 10, 2010, James Hogan wrote:
> If the device which fails to resume is part of a loadable kernel module
> it won't be checked at startup against the magic number stored in the
> RTC.
>
> Add a read-only sysfs attribute /sys/power/pm_trace_dev_hash which
> contains a list of newline separated devices (usually just the one)
> which currently match the last magic number. This allows the device
> which is failing to resume to be found after the modules are loaded
> again.
>
> Signed-off-by: James Hogan <james@albanarts.com>
> ---
> Documentation/power/s2ram.txt | 7 +++++++
> drivers/base/power/trace.c | 27 +++++++++++++++++++++++++++
> include/linux/resume-trace.h | 2 ++
> kernel/power/main.c | 18 ++++++++++++++++++
> 4 files changed, 54 insertions(+), 0 deletions(-)
>
> diff --git a/Documentation/power/s2ram.txt b/Documentation/power/s2ram.txt
> index 514b94f..3a2801a 100644
> --- a/Documentation/power/s2ram.txt
> +++ b/Documentation/power/s2ram.txt
> @@ -49,6 +49,13 @@ machine that doesn't boot) is:
> device (lspci and /sys/devices/pci* is your friend), and see if you can
> fix it, disable it, or trace into its resume function.
>
> + If no device matches the hash, it may be a device from a loadable kernel
> + module that is not loaded until after the hash is checked. You can check
> + the hash against the current devices again after more modules are loaded
> + using sysfs:
> +
> + cat /sys/power/pm_trace_dev_hash
> +

/sys/power/pm_trace_match perhaps?

How do we ensure it prints things that make sense when the last resume was
successful or the system hasn't suspended at all?

> For example, the above happens to be the VGA device on my EVO, which I
> used to run with "radeonfb" (it's an ATI Radeon mobility). It turns out
> that "radeonfb" simply cannot resume that device - it tries to set the
> diff --git a/drivers/base/power/trace.c b/drivers/base/power/trace.c
> index 17e24e3..e0cdba1 100644
> --- a/drivers/base/power/trace.c
> +++ b/drivers/base/power/trace.c
> @@ -207,6 +207,33 @@ static int show_dev_hash(unsigned int value)
>
> static unsigned int hash_value_early_read;
>
> +int snprint_trace_dev_hash(char *buf, size_t size)
> +{
> + unsigned int value = hash_value_early_read / (USERHASH * FILEHASH);
> + int ret = 0;
> + struct list_head *entry;
> +
> + device_pm_lock();
> + entry = dpm_list.prev;
> + while (size && entry != &dpm_list) {
> + struct device *dev = to_device(entry);
> + unsigned int hash = hash_string(DEVSEED, dev_name(dev),
> + DEVHASH);
> + if (hash == value) {
> + int len = snprintf(buf, size, "%s\n",
> + dev_driver_string(dev));
> + if (len > size)
> + len = size;
> + buf += len;
> + ret += len;
> + size -= len;

Don't we want to break; here and if so then why?

> + }
> + entry = entry->prev;
> + }
> + device_pm_unlock();
> + return ret;
> +}
> +
> static int early_resume_init(void)
> {
> hash_value_early_read = read_magic_time();

Thanks,
Rafael


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