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authorDavid Howells <dhowells@redhat.com>2006-10-05 09:55:46 -0400
committerDavid Howells <dhowells@warthog.cambridge.redhat.com>2006-10-05 10:10:12 -0400
commit7d12e780e003f93433d49ce78cfedf4b4c52adc5 (patch)
tree6748550400445c11a306b132009f3001e3525df8 /drivers/spi
parentda482792a6d1a3fbaaa25fae867b343fb4db3246 (diff)
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)
Diffstat (limited to 'drivers/spi')
-rw-r--r--drivers/spi/pxa2xx_spi.c4
-rw-r--r--drivers/spi/spi_mpc83xx.c3
-rw-r--r--drivers/spi/spi_s3c24xx.c2
3 files changed, 4 insertions, 5 deletions
diff --git a/drivers/spi/pxa2xx_spi.c b/drivers/spi/pxa2xx_spi.c
index 29aec77f98b..77122edeb20 100644
--- a/drivers/spi/pxa2xx_spi.c
+++ b/drivers/spi/pxa2xx_spi.c
@@ -409,7 +409,7 @@ static int wait_dma_channel_stop(int channel)
409 return limit; 409 return limit;
410} 410}
411 411
412static void dma_handler(int channel, void *data, struct pt_regs *regs) 412static void dma_handler(int channel, void *data)
413{ 413{
414 struct driver_data *drv_data = data; 414 struct driver_data *drv_data = data;
415 struct spi_message *msg = drv_data->cur_msg; 415 struct spi_message *msg = drv_data->cur_msg;
@@ -667,7 +667,7 @@ static irqreturn_t interrupt_transfer(struct driver_data *drv_data)
667 return IRQ_HANDLED; 667 return IRQ_HANDLED;
668} 668}
669 669
670static irqreturn_t ssp_int(int irq, void *dev_id, struct pt_regs *regs) 670static irqreturn_t ssp_int(int irq, void *dev_id)
671{ 671{
672 struct driver_data *drv_data = (struct driver_data *)dev_id; 672 struct driver_data *drv_data = (struct driver_data *)dev_id;
673 void *reg = drv_data->ioaddr; 673 void *reg = drv_data->ioaddr;
diff --git a/drivers/spi/spi_mpc83xx.c b/drivers/spi/spi_mpc83xx.c
index 5d92a7e5cb4..ff0b04895db 100644
--- a/drivers/spi/spi_mpc83xx.c
+++ b/drivers/spi/spi_mpc83xx.c
@@ -296,8 +296,7 @@ static int mpc83xx_spi_bufs(struct spi_device *spi, struct spi_transfer *t)
296 return t->len - mpc83xx_spi->count; 296 return t->len - mpc83xx_spi->count;
297} 297}
298 298
299irqreturn_t mpc83xx_spi_irq(s32 irq, void *context_data, 299irqreturn_t mpc83xx_spi_irq(s32 irq, void *context_data)
300 struct pt_regs * ptregs)
301{ 300{
302 struct mpc83xx_spi *mpc83xx_spi = context_data; 301 struct mpc83xx_spi *mpc83xx_spi = context_data;
303 u32 event; 302 u32 event;
diff --git a/drivers/spi/spi_s3c24xx.c b/drivers/spi/spi_s3c24xx.c
index 20eb6e95a3a..2ebe1fc4c39 100644
--- a/drivers/spi/spi_s3c24xx.c
+++ b/drivers/spi/spi_s3c24xx.c
@@ -196,7 +196,7 @@ static int s3c24xx_spi_txrx(struct spi_device *spi, struct spi_transfer *t)
196 return hw->count; 196 return hw->count;
197} 197}
198 198
199static irqreturn_t s3c24xx_spi_irq(int irq, void *dev, struct pt_regs *regs) 199static irqreturn_t s3c24xx_spi_irq(int irq, void *dev)
200{ 200{
201 struct s3c24xx_spi *hw = dev; 201 struct s3c24xx_spi *hw = dev;
202 unsigned int spsta = readb(hw->regs + S3C2410_SPSTA); 202 unsigned int spsta = readb(hw->regs + S3C2410_SPSTA);