Messages in this thread Patch in this message | | | Date | Tue, 11 Mar 2008 19:21:02 -0400 | From | Andres Salomon <> | Subject | Re: [PATCH 6/6] PM/gxfb: add hook to PM console layer that allows disabling of suspend VT switch |
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On Tue, 11 Mar 2008 19:00:11 -0400 Andres Salomon <dilinger@queued.net> wrote:
> > Prior to suspend, we allocate and switch to a new VT; after suspend, we > switch back to the original VT. This can be slow, and is completely > unnecessary if the framebuffer we're using can restore video properly. > > This adds a hook that allows drivers to select whether or not to do this > vt switch, and changes the gxfb driver to call this hook. It also > adds a module param to gxfb to allow controlling of the vt switch > (defaulting to no switch). > > (Note: I'm not convinced that console_sem is the best way to protect this, > but we should probably have some form of locking..) >
And here's a version w/out the console_sem protection. There are two races that I can think of: 1) pm_prepare_console is called with vt_switch == 0, and then pm_restore_console is called with vt_switch == 1, and 2) pm_prepare_console is called while a driver is probing, but before it has had the opportunity to call pm_set_vt_switch.
#2 is not the least bit critical, and can be ignored. I'd like some reassurances about #1.
Prior to suspend, we allocate and switch to a new VT; after suspend, we switch back to the original VT. This can be slow, and is completely unnecessary if the framebuffer we're using can restore video properly.
This adds a hook that allows drivers to select whether or not to do this vt switch, and changes the gxfb driver to call this hook. It also adds a module param to gxfb to allow controlling of the vt switch (defaulting to no switch).
Signed-off-by: Andres Salomon <dilinger@debian.org>
diff --git a/Documentation/fb/gxfb.txt b/Documentation/fb/gxfb.txt index 2d3dbaf..6749759 100644 --- a/Documentation/fb/gxfb.txt +++ b/Documentation/fb/gxfb.txt @@ -45,7 +45,8 @@ Accepted options: mode_option - specify the video mode. Of the form <x>x<y>[-<bpp>][@<refresh>] vram - size of video ram (normally auto-detected) - +vt_switch - enable vt switching during suspend/resume. The vt + switch is slow, but harmless. -- Andres Salomon <dilinger@debian.org> diff --git a/drivers/video/geode/gxfb_core.c b/drivers/video/geode/gxfb_core.c index 0cebc49..988c8e4 100644 --- a/drivers/video/geode/gxfb_core.c +++ b/drivers/video/geode/gxfb_core.c @@ -29,6 +29,7 @@ #include <linux/delay.h> #include <linux/fb.h> #include <linux/console.h> +#include <linux/suspend.h> #include <linux/init.h> #include <linux/pci.h> #include <asm/geode.h> @@ -37,6 +38,7 @@ static char *mode_option; static int vram; +static int vt_switch; /* Modes relevant to the GX (taken from modedb.c) */ static const struct fb_videomode gx_modedb[] __initdata = { @@ -388,6 +390,8 @@ static int __init gxfb_probe(struct pci_dev *pdev, const struct pci_device_id *i gxfb_check_var(&info->var, info); gxfb_set_par(info); + pm_set_vt_switch(vt_switch); + if (register_framebuffer(info) < 0) { ret = -EINVAL; goto err; @@ -508,5 +512,8 @@ MODULE_PARM_DESC(mode_option, "video mode (<x>x<y>[-<bpp>][@<refr>])"); module_param(vram, int, 0); MODULE_PARM_DESC(vram, "video memory size"); +module_param(vt_switch, int, 0); +MODULE_PARM_DESC(vt_switch, "enable VT switch during suspend/resume"); + MODULE_DESCRIPTION("Framebuffer driver for the AMD Geode GX"); MODULE_LICENSE("GPL"); diff --git a/include/linux/suspend.h b/include/linux/suspend.h index 1d7d4c5..bef66a7 100644 --- a/include/linux/suspend.h +++ b/include/linux/suspend.h @@ -12,9 +12,11 @@ #include <asm/errno.h> #if defined(CONFIG_PM_SLEEP) && defined(CONFIG_VT) && defined(CONFIG_VT_CONSOLE) +extern void pm_set_vt_switch(int); extern int pm_prepare_console(void); extern void pm_restore_console(void); #else +static inline void pm_set_vt_switch(int) {} static inline int pm_prepare_console(void) { return 0; } static inline void pm_restore_console(void) {} #endif diff --git a/kernel/power/console.c b/kernel/power/console.c index 89bcf49..327d1c6 100644 --- a/kernel/power/console.c +++ b/kernel/power/console.c @@ -7,15 +7,33 @@ #include <linux/vt_kern.h> #include <linux/kbd_kern.h> #include <linux/console.h> +#include <linux/module.h> #include "power.h" #if defined(CONFIG_VT) && defined(CONFIG_VT_CONSOLE) #define SUSPEND_CONSOLE (MAX_NR_CONSOLES-1) static int orig_fgconsole, orig_kmsg; +static int disable_vt_switch; + +/* + * Normally during a suspend, we allocate a new console and switch to it. + * When we resume, we switch back to the original console. This switch + * can be slow, so on systems where the framebuffer can handle restoration + * of video registers anyways, there's little point in doing the console + * switch. This function allows you to disable it by passing it '0'. + */ +void pm_set_vt_switch(int do_switch) +{ + disable_vt_switch = !do_switch; +} +EXPORT_SYMBOL(pm_set_vt_switch); int pm_prepare_console(void) { + if (disable_vt_switch) + return 0; + acquire_console_sem(); orig_fgconsole = fg_console; @@ -49,10 +67,12 @@ int pm_prepare_console(void) void pm_restore_console(void) { + if (disable_vt_switch) + return; + acquire_console_sem(); set_console(orig_fgconsole); release_console_sem(); kmsg_redirect = orig_kmsg; - return; } #endif
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