Blackfin: optimize startup code

Take advantage of more Blackfin-specific insns, and only initialize
registers required by the ABI.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

diff --git a/arch/blackfin/mach-common/head.S b/arch/blackfin/mach-common/head.S
index 4391621..581e2b0 100644 (file)
--- a/arch/blackfin/mach-common/head.S
+++ b/arch/blackfin/mach-common/head.S
@@ -31,6 +31,7 @@ ENDPROC(__init_clear_bss)
 ENTRY(__start)
        /* R0: argument of command line string, passed from uboot, save it */
        R7 = R0;
+
        /* Enable Cycle Counter and Nesting Of Interrupts */
 #ifdef CONFIG_BFIN_SCRATCH_REG_CYCLES
        R0 = SYSCFG_SNEN;
@@ -38,76 +39,49 @@ ENTRY(__start)
        R0 = SYSCFG_SNEN | SYSCFG_CCEN;
 #endif
        SYSCFG = R0;
-       R0 = 0;
-
-       /* Clear Out All the data and pointer Registers */
-       R1 = R0;
-       R2 = R0;
-       R3 = R0;
-       R4 = R0;
-       R5 = R0;
-       R6 = R0;
-
-       P0 = R0;
-       P1 = R0;
-       P2 = R0;
-       P3 = R0;
-       P4 = R0;
-       P5 = R0;
-
-       LC0 = r0;
-       LC1 = r0;
-       L0 = r0;
-       L1 = r0;
-       L2 = r0;
-       L3 = r0;
-
-       /* Clear Out All the DAG Registers */
-       B0 = r0;
-       B1 = r0;
-       B2 = r0;
-       B3 = r0;
-
-       I0 = r0;
-       I1 = r0;
-       I2 = r0;
-       I3 = r0;
-
-       M0 = r0;
-       M1 = r0;
-       M2 = r0;
-       M3 = r0;
+
+       /* Optimization register tricks: keep a base value in the
+        * reserved P registers so we use the load/store with an
+        * offset syntax.  R0 = [P5 + <constant>];
+        *   P5 - core MMR base
+        *   R6 - 0
+        */
+       r6 = 0;
+       p5.l = 0;
+       p5.h = hi(COREMMR_BASE);
+
+       /* Zero out registers required by Blackfin ABI */
+
+       /* Disable circular buffers */
+       L0 = r6;
+       L1 = r6;
+       L2 = r6;
+       L3 = r6;
+
+       /* Disable hardware loops in case we were started by 'go' */
+       LC0 = r6;
+       LC1 = r6;
 
        /*
         * Clear ITEST_COMMAND and DTEST_COMMAND registers,
         * Leaving these as non-zero can confuse the emulator
         */
-       p0.L = LO(DTEST_COMMAND);
-       p0.H = HI(DTEST_COMMAND);
-       [p0] = R0;
-       [p0 + (ITEST_COMMAND - DTEST_COMMAND)] = R0;
+       [p5 + (DTEST_COMMAND - COREMMR_BASE)] = r6;
+       [p5 + (ITEST_COMMAND - COREMMR_BASE)] = r6;
        CSYNC;
 
        trace_buffer_init(p0,r0);
-       P0 = R1;
-       R0 = R1;
 
        /* Turn off the icache */
-       p0.l = LO(IMEM_CONTROL);
-       p0.h = HI(IMEM_CONTROL);
-       R1 = [p0];
-       R0 = ~ENICPLB;
-       R0 = R0 & R1;
-       [p0] = R0;
+       r1 = [p5 + (IMEM_CONTROL - COREMMR_BASE)];
+       BITCLR (r1, ENICPLB_P);
+       [p5 + (IMEM_CONTROL - COREMMR_BASE)] = r1;
        SSYNC;
 
        /* Turn off the dcache */
-       p0.l = LO(DMEM_CONTROL);
-       p0.h = HI(DMEM_CONTROL);
-       R1 = [p0];
-       R0 = ~ENDCPLB;
-       R0 = R0 & R1;
-       [p0] = R0;
+       r1 = [p5 + (DMEM_CONTROL - COREMMR_BASE)];
+       BITCLR (r1, ENDCPLB_P);
+       [p5 + (DMEM_CONTROL - COREMMR_BASE)] = r1;
        SSYNC;
 
        /* in case of double faults, save a few things */
@@ -122,25 +96,25 @@ ENTRY(__start)
         * below
         */
        GET_PDA(p0, r0);
-       r6 = [p0 + PDA_DF_RETX];
+       r5 = [p0 + PDA_DF_RETX];
        p1.l = _init_saved_retx;
        p1.h = _init_saved_retx;
-       [p1] = r6;
+       [p1] = r5;
 
-       r6 = [p0 + PDA_DF_DCPLB];
+       r5 = [p0 + PDA_DF_DCPLB];
        p1.l = _init_saved_dcplb_fault_addr;
        p1.h = _init_saved_dcplb_fault_addr;
-       [p1] = r6;
+       [p1] = r5;
 
-       r6 = [p0 + PDA_DF_ICPLB];
+       r5 = [p0 + PDA_DF_ICPLB];
        p1.l = _init_saved_icplb_fault_addr;
        p1.h = _init_saved_icplb_fault_addr;
-       [p1] = r6;
+       [p1] = r5;
 
-       r6 = [p0 + PDA_DF_SEQSTAT];
+       r5 = [p0 + PDA_DF_SEQSTAT];
        p1.l = _init_saved_seqstat;
        p1.h = _init_saved_seqstat;
-       [p1] = r6;
+       [p1] = r5;
 #endif
 
        /* Initialize stack pointer */
@@ -155,7 +129,7 @@ ENTRY(__start)
        sti r0;
 #endif
 
-       r0 = 0 (x);
+       r0 = r6;
        /* Zero out all of the fun bss regions */
 #if L1_DATA_A_LENGTH > 0
        r1.l = __sbss_l1;
@@ -210,11 +184,9 @@ ENTRY(__start)
 
        /* EVT15 = _real_start */
 
-       p0.l = lo(EVT15);
-       p0.h = hi(EVT15);
        p1.l = _real_start;
        p1.h = _real_start;
-       [p0] = p1;
+       [p5 + (EVT15 - COREMMR_BASE)] = p1;
        csync;
 
 #ifdef CONFIG_EARLY_PRINTK