linux-kernel - [PATCH v4 2/2] ACPI/PPTT: Handle architecturally unknown cache types

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Message-Id: <1538666406-7504-3-git-send-email-jhugo@codeaurora.org>
Date:   Thu,  4 Oct 2018 09:20:06 -0600
From:   Jeffrey Hugo <jhugo@...eaurora.org>
To:     sudeep.holla@....com, gregkh@...uxfoundation.org,
        rjw@...ysocki.net, linux-acpi@...r.kernel.org,
        jeremy.linton@....com
Cc:     linux-kernel@...r.kernel.org, vkilari@...eaurora.org,
        Jeffrey Hugo <jhugo@...eaurora.org>
Subject: [PATCH v4 2/2] ACPI/PPTT: Handle architecturally unknown cache types

The type of a cache might not be specified by architectural mechanisms (ie
system registers), but its type might be specified in the PPTT.  In this
case, we should populate the type of the cache, rather than leave it
undefined.

This fixes the issue where the cacheinfo driver will not populate sysfs
for such caches, resulting in the information missing from utilities like
lstopo and lscpu, thus degrading the user experience.

Fixes: 2bd00bcd73e5 (ACPI/PPTT: Add Processor Properties Topology Table parsing)
Reported-by: Vijaya Kumar K <vkilari@...eaurora.org>
Signed-off-by: Jeffrey Hugo <jhugo@...eaurora.org>
Reviewed-by: Sudeep Holla <sudeep.holla@....com>
---
 drivers/acpi/pptt.c | 33 +++++++++++++--------------------
 1 file changed, 13 insertions(+), 20 deletions(-)

diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
index d1e26cb..da031b1 100644
--- a/drivers/acpi/pptt.c
+++ b/drivers/acpi/pptt.c
@@ -338,9 +338,6 @@ static struct acpi_pptt_cache *acpi_find_cache_node(struct acpi_table_header *ta
 	return found;
 }
 
-/* total number of attributes checked by the properties code */
-#define PPTT_CHECKED_ATTRIBUTES 4
-
 /**
  * update_cache_properties() - Update cacheinfo for the given processor
  * @this_leaf: Kernel cache info structure being updated
@@ -357,25 +354,15 @@ static void update_cache_properties(struct cacheinfo *this_leaf,
 				    struct acpi_pptt_cache *found_cache,
 				    struct acpi_pptt_processor *cpu_node)
 {
-	int valid_flags = 0;
-
 	this_leaf->fw_token = cpu_node;
-	if (found_cache->flags & ACPI_PPTT_SIZE_PROPERTY_VALID) {
+	if (found_cache->flags & ACPI_PPTT_SIZE_PROPERTY_VALID)
 		this_leaf->size = found_cache->size;
-		valid_flags++;
-	}
-	if (found_cache->flags & ACPI_PPTT_LINE_SIZE_VALID) {
+	if (found_cache->flags & ACPI_PPTT_LINE_SIZE_VALID)
 		this_leaf->coherency_line_size = found_cache->line_size;
-		valid_flags++;
-	}
-	if (found_cache->flags & ACPI_PPTT_NUMBER_OF_SETS_VALID) {
+	if (found_cache->flags & ACPI_PPTT_NUMBER_OF_SETS_VALID)
 		this_leaf->number_of_sets = found_cache->number_of_sets;
-		valid_flags++;
-	}
-	if (found_cache->flags & ACPI_PPTT_ASSOCIATIVITY_VALID) {
+	if (found_cache->flags & ACPI_PPTT_ASSOCIATIVITY_VALID)
 		this_leaf->ways_of_associativity = found_cache->associativity;
-		valid_flags++;
-	}
 	if (found_cache->flags & ACPI_PPTT_WRITE_POLICY_VALID) {
 		switch (found_cache->attributes & ACPI_PPTT_MASK_WRITE_POLICY) {
 		case ACPI_PPTT_CACHE_POLICY_WT:
@@ -402,11 +389,17 @@ static void update_cache_properties(struct cacheinfo *this_leaf,
 		}
 	}
 	/*
-	 * If the above flags are valid, and the cache type is NOCACHE
-	 * update the cache type as well.
+	 * If cache type is NOCACHE, then the cache hasn't been specified
+	 * via other mechanisms.  Update the type if a cache type has been
+	 * provided.
+	 *
+	 * Note, we assume such caches are unified based on conventional system
+	 * design and known examples.  Significant work is required elsewhere to
+	 * fully support data/instruction only type caches which are only
+	 * specified in PPTT.
 	 */
 	if (this_leaf->type == CACHE_TYPE_NOCACHE &&
-	    valid_flags == PPTT_CHECKED_ATTRIBUTES)
+	    found_cache->flags & ACPI_PPTT_CACHE_TYPE_VALID)
 		this_leaf->type = CACHE_TYPE_UNIFIED;
 }
 
-- 
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Qualcomm Technologies, Inc. is a member of the
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