MFC r318021,r318251:

  r318021:
    Introduce pmap_remap_vm_attr(), it allows to remap one VM memattr class to
    another.
  r318251:
    Clarify usage rules for pmap_remap_vm_attr().  Not a functional change.

2 files changed, 37 insertions, 0 deletions

diff --git a/sys/arm/arm/pmap-v6.c b/sys/arm/arm/pmap-v6.c
index 1293147..3f41192 100644
--- a/sys/arm/arm/pmap-v6.c
+++ b/sys/arm/arm/pmap-v6.c
@@ -497,6 +497,42 @@ pmap_set_tex(void)
 }
 
 /*
+ * Remap one vm_meattr class to another one. This can be useful as
+ * workaround for SOC errata, e.g. if devices must be accessed using
+ * SO memory class.
+ *
+ * !!! Please note that this function is absolutely last resort thing.
+ * It should not be used under normal circumstances. !!!
+ *
+ * Usage rules:
+ * - it shall be called after pmap_bootstrap_prepare() and before
+ *   cpu_mp_start() (thus only on boot CPU). In practice, it's expected
+ *   to be called from platform_attach() or platform_late_init().
+ *
+ * - if remapping doesn't change caching mode, or until uncached class
+ *   is remapped to any kind of cached one, then no other restriction exists.
+ *
+ * - if pmap_remap_vm_attr() changes caching mode, but both (original and
+ *   remapped) remain cached, then caller is resposible for calling
+ *   of dcache_wbinv_poc_all().
+ *
+ * - remapping of any kind of cached class to uncached is not permitted.
+ */
+void
+pmap_remap_vm_attr(vm_memattr_t old_attr, vm_memattr_t new_attr)
+{
+	int old_idx, new_idx;
+	
+	/* Map VM memattrs to indexes to tex_class table. */
+	old_idx = pte2_attr_tab[(int)old_attr];
+	new_idx = pte2_attr_tab[(int)new_attr];
+	
+	/* Replace TEX attribute and apply it. */
+	tex_class[old_idx] = tex_class[new_idx];
+	pmap_set_tex();
+}
+
+/*
  * KERNBASE must be multiple of NPT2_IN_PG * PTE1_SIZE. In other words,
  * KERNBASE is mapped by first L2 page table in L2 page table page. It
  * meets same constrain due to PT2MAP being placed just under KERNBASE.
diff --git a/sys/arm/include/pmap-v6.h b/sys/arm/include/pmap-v6.h
index 10296db..e25f7f0 100644
--- a/sys/arm/include/pmap-v6.h
+++ b/sys/arm/include/pmap-v6.h
@@ -189,6 +189,7 @@ vm_offset_t pmap_preboot_reserve_pages(u_int);
 vm_offset_t pmap_preboot_get_vpages(u_int);
 void pmap_preboot_map_attr(vm_paddr_t, vm_offset_t, vm_size_t, vm_prot_t,
     vm_memattr_t);
+void pmap_remap_vm_attr(vm_memattr_t old_attr, vm_memattr_t new_attr);
 
 #endif	/* _KERNEL */
 #endif	/* !_MACHINE_PMAP_V6_H_ */