[PATCH v2 1/1] x86/acpi: Use FADT flags to determine the PMTMR width

[Grzegorz Uriasz <gorbak25@xxxxxxxxx>]

On some computers the bit width of the PM Timer as reported
by ACPI is 32 bits when in fact the FADT flags report correctly
that the timer is 24 bits wide. On affected machines such as the
ASUS FX504GM and never gaming laptops this results in the inability
to resume the machine from suspend. Without this patch suspend is
broken on affected machines and even if a machine manages to resume
correctly then the kernel time and xen timers are trashed.

Signed-off-by: Grzegorz Uriasz <gorbak25@xxxxxxxxx>
---
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: Wei Liu <wl@xxxxxxx>
Cc: "Roger Pau Monné" <roger.pau@xxxxxxxxxx>
Cc: marmarek@xxxxxxxxxxxxxxxxxxxxxx
Cc: artur@xxxxxxxxxxxx
Cc: jakub@xxxxxxxxxxx
Cc: j.nowak26@xxxxxxxxxxxxxxxxx

Changes in v2:
- Check pm timer access width
- Proper timer width is set when xpm block is not present
- Cleanup timer initialization

---
 xen/arch/x86/acpi/boot.c    |  8 ++++++--
 xen/arch/x86/time.c         | 15 +++++++--------
 xen/include/acpi/acmacros.h |  8 ++++++++
 3 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/xen/arch/x86/acpi/boot.c b/xen/arch/x86/acpi/boot.c
index bcba52e232..8d514388b4 100644
--- a/xen/arch/x86/acpi/boot.c
+++ b/xen/arch/x86/acpi/boot.c
@@ -478,7 +478,9 @@ static int __init acpi_parse_fadt(struct acpi_table_header 
*table)
        if (fadt->header.revision >= FADT2_REVISION_ID) {
                /* FADT rev. 2 */
                if (fadt->xpm_timer_block.space_id ==
-                   ACPI_ADR_SPACE_SYSTEM_IO) {
+                   ACPI_ADR_SPACE_SYSTEM_IO &&
+                   (fadt->xpm_timer_block.access_width == 0 ||
+                   ACPI_ACCESS_BIT_WIDTH(fadt->xpm_timer_block.access_width) 
== 32)) {
                        pmtmr_ioport = fadt->xpm_timer_block.address;
                        pmtmr_width = fadt->xpm_timer_block.bit_width;
                }
@@ -490,8 +492,10 @@ static int __init acpi_parse_fadt(struct acpi_table_header 
*table)
         */
        if (!pmtmr_ioport) {
                pmtmr_ioport = fadt->pm_timer_block;
-               pmtmr_width = fadt->pm_timer_length == 4 ? 24 : 0;
+               pmtmr_width = fadt->pm_timer_length == 4 ? 32 : 0;
        }
+       if (pmtmr_width > 24 && !(fadt->flags & ACPI_FADT_32BIT_TIMER))
+               pmtmr_width = 24;
        if (pmtmr_ioport)
                printk(KERN_INFO PREFIX "PM-Timer IO Port: %#x (%u bits)\n",
                       pmtmr_ioport, pmtmr_width);
diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index d643590c0a..e9180175e0 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -457,16 +457,16 @@ static u64 read_pmtimer_count(void)
 static s64 __init init_pmtimer(struct platform_timesource *pts)
 {
     u64 start;
-    u32 count, target, mask = 0xffffff;
+    u32 count, target, mask;
 
-    if ( !pmtmr_ioport || !pmtmr_width )
+    if ( !pmtmr_ioport )
         return 0;
 
-    if ( pmtmr_width == 32 )
-    {
-        pts->counter_bits = 32;
-        mask = 0xffffffff;
-    }
+    if ( pmtmr_width != 24 && pmtmr_width != 32 )
+        return 0;
+
+    pts->counter_bits = (int) pmtmr_width;
+    mask = (1ull << pmtmr_width) - 1;
 
     count = inl(pmtmr_ioport) & mask;
     start = rdtsc_ordered();
@@ -486,7 +486,6 @@ static struct platform_timesource __initdata plt_pmtimer =
     .name = "ACPI PM Timer",
     .frequency = ACPI_PM_FREQUENCY,
     .read_counter = read_pmtimer_count,
-    .counter_bits = 24,
     .init = init_pmtimer
 };
 
diff --git a/xen/include/acpi/acmacros.h b/xen/include/acpi/acmacros.h
index 6765535053..86c503c20f 100644
--- a/xen/include/acpi/acmacros.h
+++ b/xen/include/acpi/acmacros.h
@@ -121,6 +121,14 @@
 #define ACPI_COMPARE_NAME(a,b)          (!ACPI_STRNCMP (ACPI_CAST_PTR 
(char,(a)), ACPI_CAST_PTR (char,(b)), ACPI_NAME_SIZE))
 #endif
 
+/*
+ * Algorithm to obtain access bit or byte width.
+ * Can be used with access_width of struct acpi_generic_address and 
access_size of
+ * struct acpi_resource_generic_register.
+ */
+#define ACPI_ACCESS_BIT_WIDTH(size)     (1 << ((size) + 2))
+#define ACPI_ACCESS_BYTE_WIDTH(size)    (1 << ((size) - 1))
+
 /*
  * Macros for moving data around to/from buffers that are possibly unaligned.
  * If the hardware supports the transfer of unaligned data, just do the store.
-- 
2.27.0