sh: Correct the PTRS_PER_PMD and PMD_SHIFT values

The previous expressions were wrong which made free_pmd_range() explode
when using anything other than 4KB pages (which is why 8KB and 64KB
pages were disabled with the 3-level page table layout).

The problem was that pmd_offset() was returning an index of non-zero
when it should have been returning 0. This non-zero offset was used to
calculate the address of the pmd table to free in free_pmd_range(),
which ended up trying to free an object that was not aligned on a page
boundary.

Now 3-level page tables should work with 4KB, 8KB and 64KB pages.
Signed-off-by: Matt Fleming <matt@console-pimps.org>

arch/sh/include/asm/pgtable_pmd.h

@@ -17,11 +17,11 @@
 #define USER_PTRS_PER_PGD	2
 
 /* PMD bits */
-#define PMD_SHIFT	(PAGE_SHIFT + (PAGE_SHIFT - 3))
+#define PMD_SHIFT	(PAGE_SHIFT + (PAGE_SHIFT - PTE_MAGNITUDE))
 #define PMD_SIZE	(1UL << PMD_SHIFT)
 #define PMD_MASK	(~(PMD_SIZE-1))
 
-#define PTRS_PER_PMD	(PAGE_SIZE / sizeof(pmd_t))
+#define PTRS_PER_PMD	((1 << PGDIR_SHIFT) / PMD_SIZE)
 
 #define pmd_ERROR(e) \
 	printk("%s:%d: bad pmd %016llx.\n", __FILE__, __LINE__, pmd_val(e))

arch/sh/mm/Kconfig

@@ -220,7 +220,7 @@ config PAGE_SIZE_4KB
 
 config PAGE_SIZE_8KB
 	bool "8kB"
-	depends on !MMU || X2TLB && !PGTABLE_LEVELS_3
+	depends on !MMU || X2TLB
 	help
 	  This enables 8kB pages as supported by SH-X2 and later MMUs.
 
@@ -232,7 +232,7 @@ config PAGE_SIZE_16KB
 
 config PAGE_SIZE_64KB
 	bool "64kB"
-	depends on !MMU || CPU_SH4 && !PGTABLE_LEVELS_3 || CPU_SH5
+	depends on !MMU || CPU_SH4 || CPU_SH5
 	help
 	  This enables support for 64kB pages, possible on all SH-4
 	  CPUs and later.