IRQ: Maintain regs pointer globally rather than passing to IRQ handlers

Maintain a per-CPU global "struct pt_regs *" variable which can be used instead
of passing regs around manually through all ~1800 interrupt handlers in the
Linux kernel.

The regs pointer is used in few places, but it potentially costs both stack
space and code to pass it around.  On the FRV arch, removing the regs parameter
from all the genirq function results in a 20% speed up of the IRQ exit path
(ie: from leaving timer_interrupt() to leaving do_IRQ()).

Where appropriate, an arch may override the generic storage facility and do
something different with the variable.  On FRV, for instance, the address is
maintained in GR28 at all times inside the kernel as part of general exception
handling.

Having looked over the code, it appears that the parameter may be handed down
through up to twenty or so layers of functions.  Consider a USB character
device attached to a USB hub, attached to a USB controller that posts its
interrupts through a cascaded auxiliary interrupt controller.  A character
device driver may want to pass regs to the sysrq handler through the input
layer which adds another few layers of parameter passing.

I've build this code with allyesconfig for x86_64 and i386.  I've runtested the
main part of the code on FRV and i386, though I can't test most of the drivers.
I've also done partial conversion for powerpc and MIPS - these at least compile
with minimal configurations.

This will affect all archs.  Mostly the changes should be relatively easy.
Take do_IRQ(), store the regs pointer at the beginning, saving the old one:

	struct pt_regs *old_regs = set_irq_regs(regs);

And put the old one back at the end:

	set_irq_regs(old_regs);

Don't pass regs through to generic_handle_irq() or __do_IRQ().

In timer_interrupt(), this sort of change will be necessary:

	-	update_process_times(user_mode(regs));
	-	profile_tick(CPU_PROFILING, regs);
	+	update_process_times(user_mode(get_irq_regs()));
	+	profile_tick(CPU_PROFILING);

I'd like to move update_process_times()'s use of get_irq_regs() into itself,
except that i386, alone of the archs, uses something other than user_mode().

Some notes on the interrupt handling in the drivers:

 (*) input_dev() is now gone entirely.  The regs pointer is no longer stored in
     the input_dev struct.

 (*) finish_unlinks() in drivers/usb/host/ohci-q.c needs checking.  It does
     something different depending on whether it's been supplied with a regs
     pointer or not.

 (*) Various IRQ handler function pointers have been moved to type
     irq_handler_t.

Signed-Off-By: David Howells <dhowells@redhat.com>
(cherry picked from 1b16e7ac850969f38b375e511e3fa2f474a33867 commit)

12 files changed, 14 insertions, 16 deletions

diff --git a/drivers/i2c/busses/i2c-elektor.c b/drivers/i2c/busses/i2c-elektor.c
index caa8e5c8bfbb..a591fe685f06 100644
--- a/drivers/i2c/busses/i2c-elektor.c
+++ b/drivers/i2c/busses/i2c-elektor.c
@@ -131,7 +131,7 @@ static void pcf_isa_waitforpin(void) {
 }
 
 
-static irqreturn_t pcf_isa_handler(int this_irq, void *dev_id, struct pt_regs *regs) {
+static irqreturn_t pcf_isa_handler(int this_irq, void *dev_id) {
         spin_lock(&lock);
         pcf_pending = 1;
         spin_unlock(&lock);
diff --git a/drivers/i2c/busses/i2c-ibm_iic.c b/drivers/i2c/busses/i2c-ibm_iic.c
index 80d4ba1bdfec..781a99c1647a 100644
--- a/drivers/i2c/busses/i2c-ibm_iic.c
+++ b/drivers/i2c/busses/i2c-ibm_iic.c
@@ -320,7 +320,7 @@ err:
 /*
  * IIC interrupt handler
  */
-static irqreturn_t iic_handler(int irq, void *dev_id, struct pt_regs *regs)
+static irqreturn_t iic_handler(int irq, void *dev_id)
 {
         struct ibm_iic_private* dev = (struct ibm_iic_private*)dev_id;
         volatile struct iic_regs __iomem *iic = dev->vaddr;
diff --git a/drivers/i2c/busses/i2c-iop3xx.c b/drivers/i2c/busses/i2c-iop3xx.c
index 4436c89be58e..d108ab4974cc 100644
--- a/drivers/i2c/busses/i2c-iop3xx.c
+++ b/drivers/i2c/busses/i2c-iop3xx.c
@@ -120,7 +120,7 @@ iop3xx_i2c_transaction_cleanup(struct i2c_algo_iop3xx_data *iop3xx_adap)
  * Then it passes the SR flags of interest to BH via adap data
  */
 static irqreturn_t 
-iop3xx_i2c_irq_handler(int this_irq, void *dev_id, struct pt_regs *regs) 
+iop3xx_i2c_irq_handler(int this_irq, void *dev_id) 
 {
         struct i2c_algo_iop3xx_data *iop3xx_adap = dev_id;
         u32 sr = __raw_readl(iop3xx_adap->ioaddr + SR_OFFSET);
diff --git a/drivers/i2c/busses/i2c-ite.c b/drivers/i2c/busses/i2c-ite.c
index 559a62b04ee9..f7d71869b3b9 100644
--- a/drivers/i2c/busses/i2c-ite.c
+++ b/drivers/i2c/busses/i2c-ite.c
@@ -140,8 +140,7 @@ static void iic_ite_waitforpin(void) {
 }
 
 
-static irqreturn_t iic_ite_handler(int this_irq, void *dev_id,
-                                                        struct pt_regs *regs)
+static irqreturn_t iic_ite_handler(int this_irq, void *dev_id)
 {
         spin_lock(&lock);
         iic_pending = 1;
diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c
index 155a986de516..ee65aa1be13a 100644
--- a/drivers/i2c/busses/i2c-mpc.c
+++ b/drivers/i2c/busses/i2c-mpc.c
@@ -63,7 +63,7 @@ static __inline__ void writeccr(struct mpc_i2c *i2c, u32 x)
         writeb(x, i2c->base + MPC_I2C_CR);
 }
 
-static irqreturn_t mpc_i2c_isr(int irq, void *dev_id, struct pt_regs *regs)
+static irqreturn_t mpc_i2c_isr(int irq, void *dev_id)
 {
         struct mpc_i2c *i2c = dev_id;
         if (readb(i2c->base + MPC_I2C_SR) & CSR_MIF) {
diff --git a/drivers/i2c/busses/i2c-mv64xxx.c b/drivers/i2c/busses/i2c-mv64xxx.c
index eacbaf745b64..bbc8e3a7ff55 100644
--- a/drivers/i2c/busses/i2c-mv64xxx.c
+++ b/drivers/i2c/busses/i2c-mv64xxx.c
@@ -278,7 +278,7 @@ mv64xxx_i2c_do_action(struct mv64xxx_i2c_data *drv_data)
 }
 
 static int
-mv64xxx_i2c_intr(int irq, void *dev_id, struct pt_regs *regs)
+mv64xxx_i2c_intr(int irq, void *dev_id)
 {
         struct mv64xxx_i2c_data *drv_data = dev_id;
         unsigned long   flags;
diff --git a/drivers/i2c/busses/i2c-ocores.c b/drivers/i2c/busses/i2c-ocores.c
index 3e276e958ef7..f28a76d1c0af 100644
--- a/drivers/i2c/busses/i2c-ocores.c
+++ b/drivers/i2c/busses/i2c-ocores.c
@@ -143,7 +143,7 @@ static void ocores_process(struct ocores_i2c *i2c)
         }
 }
 
-static irqreturn_t ocores_isr(int irq, void *dev_id, struct pt_regs *regs)
+static irqreturn_t ocores_isr(int irq, void *dev_id)
 {
         struct ocores_i2c *i2c = dev_id;
 
diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
index 81d87d2c2a2d..dec04da0455c 100644
--- a/drivers/i2c/busses/i2c-omap.c
+++ b/drivers/i2c/busses/i2c-omap.c
@@ -400,7 +400,7 @@ omap_i2c_ack_stat(struct omap_i2c_dev *dev, u16 stat)
 }
 
 static irqreturn_t
-omap_i2c_rev1_isr(int this_irq, void *dev_id, struct pt_regs *regs)
+omap_i2c_rev1_isr(int this_irq, void *dev_id)
 {
         struct omap_i2c_dev *dev = dev_id;
         u16 iv, w;
@@ -452,7 +452,7 @@ omap_i2c_rev1_isr(int this_irq, void *dev_id, struct pt_regs *regs)
 }
 
 static irqreturn_t
-omap_i2c_isr(int this_irq, void *dev_id, struct pt_regs *regs)
+omap_i2c_isr(int this_irq, void *dev_id)
 {
         struct omap_i2c_dev *dev = dev_id;
         u16 bits;
diff --git a/drivers/i2c/busses/i2c-pca-isa.c b/drivers/i2c/busses/i2c-pca-isa.c
index d9b4ddbad7e0..407840b6a260 100644
--- a/drivers/i2c/busses/i2c-pca-isa.c
+++ b/drivers/i2c/busses/i2c-pca-isa.c
@@ -99,7 +99,7 @@ static int pca_isa_waitforinterrupt(struct i2c_algo_pca_data *adap)
         return ret;
 }
 
-static irqreturn_t pca_handler(int this_irq, void *dev_id, struct pt_regs *regs) {
+static irqreturn_t pca_handler(int this_irq, void *dev_id) {
         wake_up_interruptible(&pca_wait);
         return IRQ_HANDLED;
 }
diff --git a/drivers/i2c/busses/i2c-pxa.c b/drivers/i2c/busses/i2c-pxa.c
index cd4ad98ad517..81050d3c9b21 100644
--- a/drivers/i2c/busses/i2c-pxa.c
+++ b/drivers/i2c/busses/i2c-pxa.c
@@ -850,7 +850,7 @@ static void i2c_pxa_irq_rxfull(struct pxa_i2c *i2c, u32 isr)
         ICR = icr;
 }
 
-static irqreturn_t i2c_pxa_handler(int this_irq, void *dev_id, struct pt_regs *regs)
+static irqreturn_t i2c_pxa_handler(int this_irq, void *dev_id)
 {
         struct pxa_i2c *i2c = dev_id;
         u32 isr = ISR;
diff --git a/drivers/i2c/busses/i2c-rpx.c b/drivers/i2c/busses/i2c-rpx.c
index 0ebec3c1a54e..8764df06f51d 100644
--- a/drivers/i2c/busses/i2c-rpx.c
+++ b/drivers/i2c/busses/i2c-rpx.c
@@ -55,10 +55,10 @@ rpx_iic_init(struct i2c_algo_8xx_data *data)
         data->i2c = (i2c8xx_t *)&(((immap_t *)IMAP_ADDR)->im_i2c);
 }
 
-static int rpx_install_isr(int irq, void (*func)(void *, void *), void *data)
+static int rpx_install_isr(int irq, void (*func)(void *), void *data)
 {
         /* install interrupt handler */
-        cpm_install_handler(irq, (void (*)(void *, struct pt_regs *)) func, data);
+        cpm_install_handler(irq, func, data);
 
         return 0;
 }
diff --git a/drivers/i2c/busses/i2c-s3c2410.c b/drivers/i2c/busses/i2c-s3c2410.c
index 9ebe429a0a0f..4ca6de209b8b 100644
--- a/drivers/i2c/busses/i2c-s3c2410.c
+++ b/drivers/i2c/busses/i2c-s3c2410.c
@@ -423,8 +423,7 @@ static int i2s_s3c_irq_nextbyte(struct s3c24xx_i2c *i2c, unsigned long iicstat)
  * top level IRQ servicing routine
 */
 
-static irqreturn_t s3c24xx_i2c_irq(int irqno, void *dev_id,
-                                   struct pt_regs *regs)
+static irqreturn_t s3c24xx_i2c_irq(int irqno, void *dev_id)
 {
         struct s3c24xx_i2c *i2c = dev_id;
         unsigned long status;