PM/gxfb: add hook to PM console layer that allows disabling of suspend VT switch
Subsystems (4)
PATCH 6/6 PM/gxfb: add hook to PM console layer that allows disabling of suspend VT switch
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..)
--- Documentation/fb/gxfb.txt | 3 ++- drivers/video/geode/gxfb_core.c | 7 +++++++ include/linux/suspend.h | 2 ++ kernel/power/console.c | 27 ++++++++++++++++++++++++++- 4 files changed, 37 insertions(+), 2 deletions(-)
Documentation/fb/gxfb.txt +2 -1
@@ -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 <[email protected]>
drivers/video/geode/gxfb_core.c +7 -0
@@ -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 *igxfb_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" );
include/linux/suspend.h +2 -0
@@ -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
kernel/power/console.c +26 -1
@@ -7,17 +7,39 @@#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) +{ +acquire_console_sem (); + disable_vt_switch = !do_switch; +release_console_sem (); +} +EXPORT_SYMBOL (pm_set_vt_switch);int pm_prepare_console (void ) {acquire_console_sem (); +if (disable_vt_switch) { +release_console_sem (); +return 0 ; + } + orig_fgconsole = fg_console;if (vc_allocate (SUSPEND_CONSOLE )) {
@@ -50,9 +72,12 @@ int pm_prepare_console(void)void pm_restore_console (void ) {acquire_console_sem (); +if (disable_vt_switch) { +release_console_sem (); +return ; + }set_console (orig_fgconsole);release_console_sem (); kmsg_redirect = orig_kmsg; -return ; }#endif
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Quoted 5 lines · On Tue, 11 Mar 2008 19:00:11 -0400 Andres Salomon <[email protected]> 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.
Quoted 8 lines
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_semis 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).
Documentation/fb/gxfb.txt +2 -1
@@ -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 <[email protected]>
drivers/video/geode/gxfb_core.c +7 -0
@@ -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 *igxfb_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" );
include/linux/suspend.h +2 -0
@@ -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
kernel/power/console.c +21 -1
@@ -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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