[PATCH 8/9] ARM: kernel: add support for cpu cache information

Hi Russell,

Thanks for the reviews.

On 25/06/14 23:33, Russell King - ARM Linux wrote:

On Wed, Jun 25, 2014 at 06:30:43PM +0100, Sudeep Holla wrote:

[...]

quoted

+
+#include <linux/bitops.h>
+#include <linux/cacheinfo.h>
+#include <linux/cpu.h>
+#include <linux/compiler.h>
+#include <linux/of.h>
+
+#include <asm/cputype.h>
+#include <asm/processor.h>
+
+#if __LINUX_ARM_ARCH__ < 7 /* pre ARMv7 */

__LINUX_ARM_ARCH__ defines the minimum architecture version we are building
for - we may support later versions than the architecture version denoted
by this symbol.  It does not define which CPUs we are building for.  Are
you sure that this is correct here?  What if we build a kernel supporting
both v6 + v7, as the OMAP guys do?

You are right, I have not considered v6 + v7, I will use cpu_architecture and
make it runtime.

quoted

+
+#define MAX_CACHE_LEVEL		1	/* Only 1 level supported */
+#define CTR_CTYPE_SHIFT		24
+#define CTR_CTYPE_MASK		(1 << CTR_CTYPE_SHIFT)
+
+struct ctr_info {
+	unsigned int cpuid_id;
+	unsigned int ctr;
+};
+
+static struct ctr_info cache_ctr_list[] = {
+};

This list needs to be populated.  Early CPUs (such as StrongARM) do not
have the CTR register.

Right, since I didn't have the list left it empty. I will compile the list
soon but I need your help. The list of StrongARM I can come up is:
1. SA-110
2. SA-1100
3. SA-1110
4. SA-1500 (grep didn't show this in kernel, not sure if it's supported)

I also have to find all other ARMv4 implementations not having CTR.

quoted

+static int get_unimplemented_ctr(unsigned int *ctr)
+{
+	int i, cpuid_id = read_cpuid_id();
+
+	for (i = 0; i < ARRAY_SIZE(cache_ctr_list); i++)
+		if (cache_ctr_list[i].cpuid_id == cpuid_id) {
+			*ctr = cache_ctr_list[i].ctr;
+			return 0;
+		}
+	return -ENOENT;
+}
+
+static unsigned int get_ctr(void)
+{
+	unsigned int ctr;
+
+	if (get_unimplemented_ctr(&ctr))
+		asm volatile ("mrc p15, 0, %0, c0, c0, 1" : "=r" (ctr));

read_cpuid_cachetype() ?

Ah, I missed to see that, will use it.

Regards,
Sudeep