linux-kernel - [PATCH 1/1] x86: Quark: Enable correct cache size/type reporting

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Date:	Mon, 29 Sep 2014 03:06:12 +0100
From:	Bryan O'Donoghue <pure.logic@...us-software.ie>
To:	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com, x86@...nel.org
Cc:	linux-kernel@...r.kernel.org,
	Bryan O'Donoghue <pure.logic@...us-software.ie>
Subject: [PATCH 1/1] x86: Quark: Enable correct cache size/type reporting

Quark X1000 lacks cpuid(4). It has cpuid(2) but returns no cache
descriptors we can work with i.e. cpuid(2) returns
eax=0x00000001 ebx=0x00000000 ecx=0x00000000 edx=0x00000000

Quark X1000 contains a 16k 4-way set associative unified L1 cache
with 256 sets

This patch emulates cpuid(4) in a similar way to other x86
processors like AMDs which don't support cpuid(4). The Quark code
is based on the existing AMD code.

Signed-off-by: Bryan O'Donoghue <pure.logic@...us-software.ie>
---
 arch/x86/kernel/cpu/intel_cacheinfo.c | 78 +++++++++++++++++++++++++++++++++--
 1 file changed, 75 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/intel_cacheinfo.c b/arch/x86/kernel/cpu/intel_cacheinfo.c
index c703507..2bee2c7 100644
--- a/arch/x86/kernel/cpu/intel_cacheinfo.c
+++ b/arch/x86/kernel/cpu/intel_cacheinfo.c
@@ -291,6 +291,70 @@ amd_cpuid4(int leaf, union _cpuid4_leaf_eax *eax,
 		(ebx->split.ways_of_associativity + 1) - 1;
 }
 
+/*
+ * Emulate cpuid4 behaviour on Intel Quark X1000
+ *
+ * Quark X1000 doesn't support CPUID(4), so this function enumerates
+ * eax, ebx and ecx for cpuid4_cache_lookup_regs
+ *
+ * Documentation states that the X1000 contains a 4-way set associative
+ * 16K cache with a 16 byte cache line and 256 lines per tag
+ *
+ * Data sources:
+ * Intel Processor Identification and the CPUID Instruction App Note 485
+ * Intel Quark SoC X1000 Core Developer's Manual 001
+ *
+ * @leaf:	Cache index
+ * @eax:	Output value for CPUID4 consistent EAX data
+ * @ebx:	Output value for CPUID4 consistent EBX data
+ * @ecx:	Output value for CPUID4 consistent ECX data
+ *
+ * @return: 0 on success, error status on failure
+ */
+static void
+intel_quark_emulate_cpuid4(int leaf, union _cpuid4_leaf_eax *eax,
+				     union _cpuid4_leaf_ebx *ebx,
+				     union _cpuid4_leaf_ecx *ecx)
+{
+	if (leaf > 0) {
+		eax->split.type = CACHE_TYPE_NULL;
+		return;
+	}
+
+	/*
+	 * Emulate CPUID4 : EAX = 0x00000123
+	 * EAX[31:26]	Num processors = 0. Implicit + 1
+	 * EAX[25:14]	Num threads sharing this cache = 0. Implicit + 1
+	 * EAX[13:10]	Reserved
+	 * EAX[9]	Fully associative cache = 0
+	 * EAX[8]	Self Initializing cache level = 1
+	 * EAX[7:5]	Cache Level = 1 - L1 cache
+	 * EAX[4:0]	Cache Type = 3 - Unified cache
+	 */
+	eax->split.num_cores_on_die = 0;
+	eax->split.num_threads_sharing = 0;
+	eax->split.is_fully_associative = 0;
+	eax->split.is_self_initializing = 1;
+	eax->split.type = CACHE_TYPE_UNIFIED;
+	eax->split.level = 1;
+
+	/*
+	 * Emulate CPUID4 : EBX = 0x00C0000F
+	 * EBX[31:22]	Ways of Associativity = 3. Implicit + 1
+	 * EBX[21:12]	Physical Line partitions = 0. Implicit + 1
+	 * EBX[11:0]	System Coherency Line Size = 15. Implicit +1
+	 */
+	ebx->split.ways_of_associativity = 3;
+	ebx->split.physical_line_partition = 0;
+	ebx->split.coherency_line_size = 15;
+
+	/*
+	 * Emulate CPUID4 : ECX 0x000000FF
+	 * ECX[31:0]	Number of sets = 255. Implicit +1
+	 */
+	ecx->split.number_of_sets = 255;
+}
+
 struct _cache_attr {
 	struct attribute attr;
 	ssize_t (*show)(struct _cpuid4_info *, char *, unsigned int);
@@ -543,9 +607,12 @@ cpuid4_cache_lookup_regs(int index, struct _cpuid4_info_regs *this_leaf)
 			amd_cpuid4(index, &eax, &ebx, &ecx);
 		amd_init_l3_cache(this_leaf, index);
 	} else {
-		cpuid_count(4, index, &eax.full, &ebx.full, &ecx.full, &edx);
+		if (boot_cpu_data.x86 == 5 && boot_cpu_data.x86_model == 9)
+			intel_quark_emulate_cpuid4(index, &eax, &ebx, &ecx);
+		else
+			cpuid_count(4, index, &eax.full, &ebx.full,
+				    &ecx.full, &edx);
 	}
-
 	if (eax.split.type == CACHE_TYPE_NULL)
 		return -EIO; /* better error ? */
 
@@ -569,13 +636,16 @@ static int find_num_cache_leaves(struct cpuinfo_x86 *c)
 		op = 0x8000001d;
 	else
 		op = 4;
-
 	do {
 		++i;
 		/* Do cpuid(op) loop to find out num_cache_leaves */
 		cpuid_count(op, i, &eax, &ebx, &ecx, &edx);
 		cache_eax.full = eax;
 	} while (cache_eax.split.type != CACHE_TYPE_NULL);
+
+	if (c->x86 == 5 && c->x86_model == 9)
+		i = 1;
+
 	return i;
 }
 
@@ -630,6 +700,8 @@ unsigned int init_intel_cacheinfo(struct cpuinfo_x86 *c)
 					new_l1d = this_leaf.size/1024;
 				else if (this_leaf.eax.split.type == CACHE_TYPE_INST)
 					new_l1i = this_leaf.size/1024;
+				else if (this_leaf.eax.split.type == CACHE_TYPE_UNIFIED)
+					new_l1d = new_l1i = this_leaf.size/1024/2;
 				break;
 			case 2:
 				new_l2 = this_leaf.size/1024;
-- 
1.9.1

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