[meta-freescale] [meta-fsl-arm-extra][PATCH] linux-wandboard: Configure the ARM core to use hardware performance counters.

[Fabio Estevam]

On Sun, Dec 21, 2014 at 2:06 PM, Alex Gonzalez <alex.gonzalez at digi.com> wrote:
> Without this patch the performance counters in the Cortex A9 core always
> return zero.

I suppose you have a JTAG cable connected to the board as per
"ERR006259 ARM: Debug/trace functions (PMU, PTM and ETB) are disabled
with absence of JTAG_TCK clock after POR" , right?


> Signed-off-by: Alex Gonzalez <alex.gonzalez at digi.com>
> ---
>  ...6q-Set-non-invasive-debug-configuration-p.patch | 42 ++++++++++++++++++++++
>  recipes-kernel/linux/linux-wandboard_3.10.17.bb    |  2 ++
>  2 files changed, 44 insertions(+)
>  create mode 100644 recipes-kernel/linux/linux-wandboard-3.10.17/0001-ARM-imx-imx6q-Set-non-invasive-debug-configuration-p.patch
>
> diff --git a/recipes-kernel/linux/linux-wandboard-3.10.17/0001-ARM-imx-imx6q-Set-non-invasive-debug-configuration-p.patch b/recipes-kernel/linux/linux-wandboard-3.10.17/0001-ARM-imx-imx6q-Set-non-invasive-debug-configuration-p.patch
> new file mode 100644
> index 000000000000..69826afe25e2
> --- /dev/null
> +++ b/recipes-kernel/linux/linux-wandboard-3.10.17/0001-ARM-imx-imx6q-Set-non-invasive-debug-configuration-p.patch
> @@ -0,0 +1,42 @@
> +From: Alex Gonzalez <alex.gonzalez at digi.com>
> +Date: Sun, 21 Dec 2014 16:04:56 +0100
> +Subject: [PATCH] ARM: imx: imx6q: Set non invasive debug configuration
> + permission bits.
> +
> +This is needed in order to use the hardware performance events counters.
> +
> +http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.faqs/ka16431.html
> +
> +Signed-off-by: Alex Gonzalez <alex.gonzalez at digi.com>
> +---
> + arch/arm/mach-imx/mach-imx6q.c | 10 ++++++++++
> + 1 file changed, 10 insertions(+)
> +
> +diff --git a/arch/arm/mach-imx/mach-imx6q.c b/arch/arm/mach-imx/mach-imx6q.c
> +index 5fb11af5643d..e54906a8d442 100644
> +--- a/arch/arm/mach-imx/mach-imx6q.c
> ++++ b/arch/arm/mach-imx/mach-imx6q.c
> +@@ -304,6 +304,15 @@ static const struct of_dev_auxdata imx6q_auxdata_lookup[] __initconst = {
> +       { /* sentinel */ }
> + };
> +
> ++static void imx6q_armpmu_init(void)
> ++{
> ++      /* Configure the non invasive debug configuration registers */
> ++      if (IS_ENABLED(CONFIG_HW_PERF_EVENTS)) {
> ++              u32 val = 0b11;
> ++              asm volatile("mcr p15, 0, %0, c1, c1, 1" : : "r" (val));

Wouldn't this be required for all CortexA9 instead of mx6 only?

It would be nice if you could send this to the linux-arm-kernel for
review and proper discussion.

Thanks