[RFC , PATCH] support for the ibm,pa_features cpu property

[Will Schmidt <will_schmidt@vnet.ibm.com>]

To determine if our processors support some features, such as large
pages, we should be using the ibm,pa_features property, rather than just
the PVR values.  
This is an initial pass at the functionality.  This has been tested in
the case where the property is missing, but still needs to be tested
against a system where the property actually exists.  :-o  



diff --git a/arch/powerpc/kernel/setup_64.c
b/arch/powerpc/kernel/setup_64.c
index 13e91c4..78ad054 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -106,6 +106,65 @@ static struct notifier_block ppc64_panic
 	.priority = INT_MIN /* may not return; must be done last */
 };
 
+/*
+ * ibm,pa-features is a per-cpu property that contains a 2 byte header
+ * plus up to 256 bytes worth of processor attributes.  First header
+ * byte specifies the number of bytes implemented by the platform.
+ * Second header byte is an "attribute-specifier" type, which should
+ * be zero.  Remainder of the data consists of ones and zeros.
+ * Implementation:  Pass in the byte and bit offset for the feature
+ * that we are interested in.  The function will return -1 if the
+ * pa-features property is missing, or a 1/0 to indicate if the feature
+ * is supported/not supported.
+ */
+
+static int get_pa_features(int pabyte,int pabit)
+{
+	struct device_node *cpu;
+	char *pa_feature_table;
+
+	cpu = of_find_node_by_type(NULL, "cpu");
+	pa_feature_table = 
+		(char *)get_property(cpu, "ibm,pa-features", NULL);
+
+	if ( pa_feature_table == NULL ) {
+		printk("ibm,pa-features property is missing.\n");
+		return -1;
+	}
+
+	/* sanity check */
+	if ( pabyte > pa_feature_table[0] ) {
+		printk("%s: %d out of range for table of size %d\n",
+			__FUNCTION__,pabyte,pa_feature_table[0]);
+		return -1;
+	}
+	
+	return pa_feature_table[2+pabyte*8+pabit];
+}
+
+/*
+ * set values within the cur_cpu_spec table according to
+ * the ibm,pa_features property. 
+ * potential entries include: 
+ * Byte 0, bit 1 - FPU available
+ * Byte 1, bit 2 - Large Pages 
+ * Byte 2, bit 3 - DAR set on alignment Interrupt. 
+ */
+static void add_cpu_features()
+{
+	/* if no property, bail early */
+	if (get_pa_features(0,0) == -1 ) return;
+
+	if (get_pa_features(1,2) ) {
+		printk("Adding CI_LARGE_PAGE to cur_cpu_spec \n");
+		cur_cpu_spec->cpu_features |= CPU_FTR_CI_LARGE_PAGE;
+	}
+
+	/* add more here... */
+
+}
+
+
 #ifdef CONFIG_SMP
 
 static int smt_enabled_cmdline;
@@ -425,6 +484,8 @@ void __init setup_system(void)
 
 	parse_early_param();
 
+	add_cpu_features();
+
 	check_smt_enabled();
 	smp_setup_cpu_maps();