[PATCH v4 ppisa] arm/xilinx_zynq: ensure that cache is cleaned and MMU disabled when initialization starts.

[Pavel Pisa]

The u-boot loader enables the MMU plus the data and instruction caches
in some versions which results in RTEMS boot failure.

Closes #2774.
---
 .../libbsp/arm/xilinx-zynq/startup/bspstarthooks.c | 35 ++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/c/src/lib/libbsp/arm/xilinx-zynq/startup/bspstarthooks.c b/c/src/lib/libbsp/arm/xilinx-zynq/startup/bspstarthooks.c
index 58f5ec6..5372380 100644
--- a/c/src/lib/libbsp/arm/xilinx-zynq/startup/bspstarthooks.c
+++ b/c/src/lib/libbsp/arm/xilinx-zynq/startup/bspstarthooks.c
@@ -21,6 +21,41 @@
 
 BSP_START_TEXT_SECTION void bsp_start_hook_0(void)
 {
+  uint32_t sctlr_val;
+
+  sctlr_val = arm_cp15_get_control();
+
+  /*
+   * Current U-boot loader seems to start kernel image
+   * with I and D caches on and MMU enabled.
+   * If RTEMS application image finds that cache is on
+   * during startup then disable caches.
+   */
+  if ( sctlr_val & (ARM_CP15_CTRL_I | ARM_CP15_CTRL_C | ARM_CP15_CTRL_M ) ) {
+    if ( sctlr_val & (ARM_CP15_CTRL_C | ARM_CP15_CTRL_M ) ) {
+      /*
+       * If the data cache is on then ensure that it is clean
+       * before switching off to be extra carefull.
+       */
+      arm_cp15_data_cache_clean_all_levels();
+    }
+    arm_cp15_flush_prefetch_buffer();
+    sctlr_val &= ~ ( ARM_CP15_CTRL_I | ARM_CP15_CTRL_C | ARM_CP15_CTRL_M | ARM_CP15_CTRL_A );
+    arm_cp15_set_control( sctlr_val );
+  }
+  arm_cp15_instruction_cache_invalidate();
+  /*
+   * The care should be taken there that no shared levels
+   * are invalidated by secondary CPUs in SMP case.
+   * It is not problem on Zynq because level of coherency
+   * is L1 only and higher level is not maintained and seen
+   * by CP15. So no special care to limit levels on the secondary
+   * are required there.
+   */
+  arm_cp15_data_cache_invalidate_all_levels();
+  arm_cp15_branch_predictor_invalidate_all();
+  arm_cp15_tlb_invalidate();
+  arm_cp15_flush_prefetch_buffer();
   arm_a9mpcore_start_hook_0();
 }
 
-- 
1.9.1