[PATCHv3,1/2] ARM: imx53: add secure-reg-access support for PMU

Commit Message

Sebastian Reichel Feb. 9, 2018, 5:03 p.m. UTC

On i.MX53 it is necessary to set the DBG_EN bit in the
platform GPC register to enable access to PMU counters
other than the cycle counter.

Signed-off-by: Sebastian Reichel <[e-mail]>
---
 arch/arm/mach-imx/mach-imx53.c | 41 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 40 insertions(+), 1 deletion(-)

Comments

Fabio Estevam Feb. 9, 2018, 8:08 p.m. UTC | #1

On Fri, Feb 9, 2018 at 3:03 PM, Sebastian Reichel
<[e-mail]> wrote:

> +       gpc_reg = ioremap(MXC_CORTEXA8_PLAT_GPC, 4);
> +       if (!gpc_reg) {
> +               pr_warning("unable to map GPC to enable perf\n");
> +               return;
> +       }
> +
> +       gpc = __raw_readl(gpc_reg);

You could use readl_relaxed() instead.

> +       gpc |= GPC_DBG_EN;
> +       __raw_writel(gpc, gpc_reg);

You could use writel_relaxed() instead.

> +
> +       return;

This 'return' can be removed.

> +}

Patch

diff --git a/arch/arm/mach-imx/mach-imx53.c b/arch/arm/mach-imx/mach-imx53.c
index 07c2e8dca494..661777ee1cc4 100644
--- a/arch/arm/mach-imx/mach-imx53.c
+++ b/arch/arm/mach-imx/mach-imx53.c
@@ -28,10 +28,49 @@  static void __init imx53_init_early(void)
 	mxc_set_cpu_type(MXC_CPU_MX53);
 }
 
+#define MXC_CORTEXA8_PLAT_GPC 0x63fa0004
+#define GPC_DBG_EN BIT(16)
+
+/*
+ * This enables the DBGEN bit in ARM_GPC register, which is
+ * required for accessing some performance counter features.
+ * Technically it is only required while perf is used, but to
+ * keep the source code simple we just enable it all the time
+ * when the kernel configuration allows using the feature.
+ */
+static void imx53_pmu_init(void)
+{
+	void __iomem *gpc_reg;
+	struct device_node *node;
+	u32 gpc;
+
+	if (!IS_ENABLED(CONFIG_ARM_PMU))
+		return;
+
+	node = of_find_compatible_node(NULL, NULL, "arm,cortex-a8-pmu");
+	if (!node)
+		return;
+
+	if (!of_property_read_bool(node, "secure-reg-access"))
+		return;
+
+	gpc_reg = ioremap(MXC_CORTEXA8_PLAT_GPC, 4);
+	if (!gpc_reg) {
+		pr_warning("unable to map GPC to enable perf\n");
+		return;
+	}
+
+	gpc = __raw_readl(gpc_reg);
+	gpc |= GPC_DBG_EN;
+	__raw_writel(gpc, gpc_reg);
+
+	return;
+}
+
 static void __init imx53_dt_init(void)
 {
 	imx_src_init();
-
+	imx53_pmu_init();
 	imx_aips_allow_unprivileged_access("fsl,imx53-aipstz");
 }