[PATCH] POWER9 PMU stops after idle workaround

[Madhavan Srinivasan]

On Thursday 20 July 2017 07:23 AM, Nicholas Piggin wrote:
> POWER9 DD2 PMU can stop after a state-loss idle in some conditions.
>
> A solution is to set then clear MMCRA[60] after wake from state-loss
> idle.
Acked-by: Madhavan Srinivasan <maddy at linux.vnet.ibm.com>

>
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
> ---
>   arch/powerpc/kernel/idle_book3s.S | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
> index 516ebef905c0..e6252c5a57a4 100644
> --- a/arch/powerpc/kernel/idle_book3s.S
> +++ b/arch/powerpc/kernel/idle_book3s.S
> @@ -460,11 +460,17 @@ pnv_restore_hyp_resource_arch300:
>   	/*
>   	 * Workaround for POWER9, if we lost resources, the ERAT
>   	 * might have been mixed up and needs flushing. We also need
> -	 * to reload MMCR0 (see comment above).
> +	 * to reload MMCR0 (see comment above). We also need to set
> +	 * then clear bit 60 in MMCRA to ensure the PMU starts running.
>   	 */
>   	blt	cr3,1f
>   	PPC_INVALIDATE_ERAT
>   	ld	r1,PACAR1(r13)
> +	mfspr	r4,SPRN_MMCRA
> +	ori	r4,r4,(1 << (63-60))
> +	mtspr	SPRN_MMCRA,r4
> +	xori	r4,r4,(1 << (63-60))
> +	mtspr	SPRN_MMCRA,r4
>   	ld	r4,_MMCR0(r1)
>   	mtspr	SPRN_MMCR0,r4
>   1: