On Monday, February 04, 2013 01:37:20 PM Jesse Barnes wrote:
> KMS drivers can potentially restore the display configuration without
> userspace help. Such drivers can can call a new funciton,
> pm_vt_switch_required(false) if they support this feature. In that
> case, the PM layer won't VT switch to the suspend console at suspend
> time and then back to the original VT on resume, but rather leave things
> alone for a nicer looking suspend and resume sequence.
>
> v2: make a function so we can handle multiple drivers (Alan)
> v3: use a list to track device requests (Rafael)
>
> Signed-off-by: Jesse Barnes <jbarnes at virtuousgeek.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
for all [1-3/3].
Thanks,
Rafael
> ---
> include/linux/pm.h | 4 ++
> kernel/power/console.c | 115 ++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 119 insertions(+)
>
> diff --git a/include/linux/pm.h b/include/linux/pm.h
> index 03d7bb1..98310eb 100644
> --- a/include/linux/pm.h
> +++ b/include/linux/pm.h
> @@ -35,6 +35,10 @@ extern void (*pm_idle)(void);
> extern void (*pm_power_off)(void);
> extern void (*pm_power_off_prepare)(void);
>
> +struct device; /* we have a circular dep with device.h */
> +extern void pm_vt_switch_required(struct device *dev, bool required);
> +extern void pm_vt_switch_unregister(struct device *dev);
> +
> /*
> * Device power management
> */
> diff --git a/kernel/power/console.c b/kernel/power/console.c
> index b1dc456..4871ca9 100644
> --- a/kernel/power/console.c
> +++ b/kernel/power/console.c
> @@ -4,6 +4,7 @@
> * Originally from swsusp.
> */
>
> +#include <linux/console.h>
> #include <linux/vt_kern.h>
> #include <linux/kbd_kern.h>
> #include <linux/vt.h>
> @@ -14,8 +15,119 @@
>
> static int orig_fgconsole, orig_kmsg;
>
> +DEFINE_MUTEX(vt_switch_mutex);
> +
> +struct pm_vt_switch {
> + struct list_head head;
> + struct device *dev;
> + bool required;
> +};
> +
> +LIST_HEAD(pm_vt_switch_list);
> +
> +
> +/**
> + * pm_vt_switch_required - indicate VT switch at suspend requirements
> + * @dev: device
> + * @required: if true, caller needs VT switch at suspend/resume time
> + *
> + * The different console drivers may or may not require VT switches across
> + * suspend/resume, depending on how they handle restoring video state and
> + * what may be running.
> + *
> + * Drivers can indicate support for switchless suspend/resume, which can
> + * save time and flicker, by using this routine and passing 'false' as
> + * the argument. If any loaded driver needs VT switching, or the
> + * no_console_suspend argument has been passed on the command line, VT
> + * switches will occur.
> + */
> +void pm_vt_switch_required(struct device *dev, bool required)
> +{
> + struct pm_vt_switch *entry, *tmp;
> +
> + mutex_lock(&vt_switch_mutex);
> + list_for_each_entry(tmp, &pm_vt_switch_list, head) {
> + if (tmp->dev == dev) {
> + /* already registered, update requirement */
> + tmp->required = required;
> + goto out;
> + }
> + }
> +
> + entry = kmalloc(sizeof(*entry), GFP_KERNEL);
> + if (!entry)
> + goto out;
> +
> + entry->required = required;
> + entry->dev = dev;
> +
> + list_add(&entry->head, &pm_vt_switch_list);
> +out:
> + mutex_unlock(&vt_switch_mutex);
> +}
> +EXPORT_SYMBOL(pm_vt_switch_required);
> +
> +/**
> + * pm_vt_switch_unregister - stop tracking a device's VT switching needs
> + * @dev: device
> + *
> + * Remove @dev from the vt switch list.
> + */
> +void pm_vt_switch_unregister(struct device *dev)
> +{
> + struct pm_vt_switch *tmp;
> +
> + mutex_lock(&vt_switch_mutex);
> + list_for_each_entry(tmp, &pm_vt_switch_list, head) {
> + if (tmp->dev == dev) {
> + list_del(&tmp->head);
> + break;
> + }
> + }
> + mutex_unlock(&vt_switch_mutex);
> +}
> +
> +/*
> + * There are three cases when a VT switch on suspend/resume are required:
> + * 1) no driver has indicated a requirement one way or another, so preserve
> + * the old behavior
> + * 2) console suspend is disabled, we want to see debug messages across
> + * suspend/resume
> + * 3) any registered driver indicates it needs a VT switch
> + *
> + * If none of these conditions is present, meaning we have at least one driver
> + * that doesn't need the switch, and none that do, we can avoid it to make
> + * resume look a little prettier (and suspend too, but that's usually hidden,
> + * e.g. when closing the lid on a laptop).
> + */
> +static bool pm_vt_switch(void)
> +{
> + struct pm_vt_switch *entry;
> + bool ret = true;
> +
> + mutex_lock(&vt_switch_mutex);
> + if (list_empty(&pm_vt_switch_list))
> + goto out;
> +
> + if (!console_suspend_enabled)
> + goto out;
> +
> + list_for_each_entry(entry, &pm_vt_switch_list, head) {
> + if (entry->required)
> + goto out;
> + }
> +
> + ret = false;
> +out:
> + mutex_unlock(&vt_switch_mutex);
> + return ret;
> +}
> +
> int pm_prepare_console(void)
> {
> + if (!pm_vt_switch())
> + return 0;
> +
> orig_fgconsole = vt_move_to_console(SUSPEND_CONSOLE, 1);
> if (orig_fgconsole < 0)
> return 1;
> @@ -26,6 +138,9 @@ int pm_prepare_console(void)
>
> void pm_restore_console(void)
> {
> + if (!pm_vt_switch())
> + return;
> +
> if (orig_fgconsole >= 0) {
> vt_move_to_console(orig_fgconsole, 0);
> vt_kmsg_redirect(orig_kmsg);
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
