[PATCH v2 02/24] EDAC, ghes: Fix grain calculation

[Robert Richter]

The conversion from the physical address mask to a grain (defined as
granularity in bytes) is broken:

	e->grain = ~(mem_err->physical_addr_mask & ~PAGE_MASK);

E.g., a physical address mask of ~0xfff should give a grain of 0x1000,
instead the grain is wrong with the upper bits always set. We also
remove the limitation to the page size as the granularity is unrelated
to the page size used in the system. We fix this with:

	e->grain = ~mem_err->physical_addr_mask + 1;

Note: We need to adopt the grain_bits calculation as e->grain is now a
power of 2 and no longer a bit mask. The formula is now the same as in
edac_mc and can later be unified.

Signed-off-by: Robert Richter <rrichter@xxxxxxxxxxx>
---
 drivers/edac/ghes_edac.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/edac/ghes_edac.c b/drivers/edac/ghes_edac.c
index 7f19f1c672c3..d095d98d6a8d 100644
--- a/drivers/edac/ghes_edac.c
+++ b/drivers/edac/ghes_edac.c
@@ -222,6 +222,7 @@ void ghes_edac_report_mem_error(int sev, struct cper_sec_mem_err *mem_err)
 	/* Cleans the error report buffer */
 	memset(e, 0, sizeof (*e));
 	e->error_count = 1;
+	e->grain = 1;
 	strcpy(e->label, "unknown label");
 	e->msg = pvt->msg;
 	e->other_detail = pvt->other_detail;
@@ -317,7 +318,7 @@ void ghes_edac_report_mem_error(int sev, struct cper_sec_mem_err *mem_err)
 
 	/* Error grain */
 	if (mem_err->validation_bits & CPER_MEM_VALID_PA_MASK)
-		e->grain = ~(mem_err->physical_addr_mask & ~PAGE_MASK);
+		e->grain = ~mem_err->physical_addr_mask + 1;
 
 	/* Memory error location, mapped on e->location */
 	p = e->location;
@@ -433,8 +434,15 @@ void ghes_edac_report_mem_error(int sev, struct cper_sec_mem_err *mem_err)
 	if (p > pvt->other_detail)
 		*(p - 1) = '\0';
 
+	/*
+	 * We expect the hw to report a reasonable grain, fallback to
+	 * 1 byte granularity otherwise.
+	 */
+	if (WARN_ON_ONCE(!e->grain))
+		e->grain = 1;
+	grain_bits = fls_long(e->grain - 1);
+
 	/* Generate the trace event */
-	grain_bits = fls_long(e->grain);
 	snprintf(pvt->detail_location, sizeof(pvt->detail_location),
 		 "APEI location: %s %s", e->location, e->other_detail);
 	trace_mc_event(type, e->msg, e->label, e->error_count,
-- 
2.20.1