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authorPaul Mundt <lethal@linux-sh.org>2006-09-27 16:01:12 +0900
committerPaul Mundt <lethal@linux-sh.org>2006-09-27 16:01:12 +0900
commitf1517494407b1f1ca0063a756cc30d75e96d433c (patch)
treefe7827210e76750687de601e6b0695a4e4e16fa7
parent5283ecb5ccbdb90d49fce6488d3944bba63a591c (diff)
sh: Cleanup and document register bank usage.
Initial register bank cleanup. Make SR.RB configurable, and add some preliminary documentation on register bank usage within the kernel. Signed-off-by: Paul Mundt <lethal@linux-sh.org>
-rw-r--r--Documentation/sh/register-banks.txt33
-rw-r--r--include/asm-sh/system.h17
-rw-r--r--include/asm-sh/thread_info.h17
3 files changed, 64 insertions, 3 deletions
diff --git a/Documentation/sh/register-banks.txt b/Documentation/sh/register-banks.txt
new file mode 100644
index 00000000000..a6719f2f659
--- /dev/null
+++ b/Documentation/sh/register-banks.txt
@@ -0,0 +1,33 @@
+ Notes on register bank usage in the kernel
+ ==========================================
+
+Introduction
+------------
+
+The SH-3 and SH-4 CPU families traditionally include a single partial register
+bank (selected by SR.RB, only r0 ... r7 are banked), whereas other families
+may have more full-featured banking or simply no such capabilities at all.
+
+SR.RB banking
+-------------
+
+In the case of this type of banking, banked registers are mapped directly to
+r0 ... r7 if SR.RB is set to the bank we are interested in, otherwise ldc/stc
+can still be used to reference the banked registers (as r0_bank ... r7_bank)
+when in the context of another bank. The developer must keep the SR.RB value
+in mind when writing code that utilizes these banked registers, for obvious
+reasons. Userspace is also not able to poke at the bank1 values, so these can
+be used rather effectively as scratch registers by the kernel.
+
+Presently the kernel uses several of these registers.
+
+ - r0_bank, r1_bank (referenced as k0 and k1, used for scratch
+ registers when doing exception handling).
+ - r2_bank (used to track the EXPEVT/INTEVT code)
+ - Used by do_IRQ() and friends for doing irq mapping based off
+ of the interrupt exception vector jump table offset
+ - r6_bank (global interrupt mask)
+ - The SR.IMASK interrupt handler makes use of this to set the
+ interrupt priority level (used by local_irq_enable())
+ - r7_bank (current)
+
diff --git a/include/asm-sh/system.h b/include/asm-sh/system.h
index 1630a5411e5..198d17e3069 100644
--- a/include/asm-sh/system.h
+++ b/include/asm-sh/system.h
@@ -136,7 +136,8 @@ extern void __xchg_called_with_bad_pointer(void);
#define set_mb(var, value) do { xchg(&var, value); } while (0)
/* Interrupt Control */
-static __inline__ void local_irq_enable(void)
+#ifdef CONFIG_CPU_HAS_SR_RB
+static inline void local_irq_enable(void)
{
unsigned long __dummy0, __dummy1;
@@ -149,6 +150,20 @@ static __inline__ void local_irq_enable(void)
: "1" (~0x000000f0)
: "memory");
}
+#else
+static inline void local_irq_enable(void)
+{
+ unsigned long __dummy0, __dummy1;
+
+ __asm__ __volatile__ (
+ "stc sr, %0\n\t"
+ "and %1, %0\n\t"
+ "ldc %0, sr\n\t"
+ : "=&r" (__dummy0), "=r" (__dummy1)
+ : "1" (~0x000000f0)
+ : "memory");
+}
+#endif
static __inline__ void local_irq_disable(void)
{
diff --git a/include/asm-sh/thread_info.h b/include/asm-sh/thread_info.h
index 7345350d98c..f64dd803a01 100644
--- a/include/asm-sh/thread_info.h
+++ b/include/asm-sh/thread_info.h
@@ -48,16 +48,29 @@ struct thread_info {
#define init_thread_info (init_thread_union.thread_info)
#define init_stack (init_thread_union.stack)
+#define THREAD_SIZE (2*PAGE_SIZE)
+
/* how to get the thread information struct from C */
static inline struct thread_info *current_thread_info(void)
{
struct thread_info *ti;
+#ifdef CONFIG_CPU_HAS_SR_RB
__asm__("stc r7_bank, %0" : "=r" (ti));
+#else
+ unsigned long __dummy;
+
+ __asm__ __volatile__ (
+ "mov r15, %0\n\t"
+ "and %1, %0\n\t"
+ : "=&r" (ti), "=r" (__dummy)
+ : "1" (~(THREAD_SIZE - 1))
+ : "memory");
+#endif
+
return ti;
}
/* thread information allocation */
-#define THREAD_SIZE (2*PAGE_SIZE)
#define alloc_thread_info(ti) ((struct thread_info *) __get_free_pages(GFP_KERNEL,1))
#define free_thread_info(ti) free_pages((unsigned long) (ti), 1)
@@ -65,7 +78,7 @@ static inline struct thread_info *current_thread_info(void)
/* how to get the thread information struct from ASM */
#define GET_THREAD_INFO(reg) \
- stc r7_bank, reg
+ stc r7_bank, reg
#endif