Re: [PATCH] powerpc/powernv/idle: add a basic stop 0-3 driver for POWER10

From: Gautham R Shenoy <ego@linux.vnet.ibm.com>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: Ryan P Grimm <rgrimm@us.ibm.com>,
	Michael Neuling <mikey@neuling.org>,
	linuxppc-dev@lists.ozlabs.org,
	Pratik Rajesh Sampat <psampat@linux.ibm.com>,
	"Gautham R . Shenoy" <ego@linux.vnet.ibm.com>
Subject: Re: [PATCH] powerpc/powernv/idle: add a basic stop 0-3 driver for POWER10
Date: Wed, 19 Aug 2020 23:06:56 +0530	[thread overview]
Message-ID: <20200819173656.GA21538@in.ibm.com> (raw)
In-Reply-To: <20200819094700.493399-1-npiggin@gmail.com>

On Wed, Aug 19, 2020 at 07:47:00PM +1000, Nicholas Piggin wrote:
> This driver does not restore stop > 3 state, so it limits itself
> to states which do not lose full state or TB.
> 
> The POWER10 SPRs are sufficiently different from P9 that it seems
> easier to split out the P10 code. The POWER10 deep sleep code
> (e.g., the BHRB restore) has been taken out, but it can be re-added
> when stop > 3 support is added.

MMCRA[BHRB] save/restore was in the shallow stop-state path. But we
can add it back later.

> 
> Cc: Ryan P Grimm <rgrimm@us.ibm.com>
> Cc: Michael Neuling <mikey@neuling.org>
> Cc: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
> Cc: Pratik Rajesh Sampat <psampat@linux.ibm.com>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

Just a minor comment below. But otherwise the patch looks good to me.

[..snip..]

> @@ -1093,11 +1200,15 @@ int validate_psscr_val_mask(u64 *psscr_val, u64 *psscr_mask, u32 flags)
>   * @dt_idle_states: Number of idle state entries
>   * Returns 0 on success
>   */
> -static void __init pnv_power9_idle_init(void)
> +static void __init pnv_arch300_idle_init(void)
>  {
>  	u64 max_residency_ns = 0;
>  	int i;
> 
> +	/* stop is not really architected, we only have p9,p10 drivers */
> +	if (!pvr_version_is(PVR_POWER10) && !pvr_version_is(PVR_POWER9))
> +		return;
> +
>  	/*
>  	 * pnv_deepest_stop_{val,mask} should be set to values corresponding to
>  	 * the deepest stop state.
> @@ -1112,6 +1223,11 @@ static void __init pnv_power9_idle_init(void)
>  		struct pnv_idle_states_t *state = &pnv_idle_states[i];
>  		u64 psscr_rl = state->psscr_val & PSSCR_RL_MASK;
> 
> +		/* No deep loss driver implemented for POWER10 yet */
> +		if (pvr_version_is(PVR_POWER10) &&
> +				state->flags & (OPAL_PM_TIMEBASE_STOP|OPAL_PM_LOSE_FULL_CONTEXT))
> +			continue;
> +

Should we have a pr_info() informing the user the kernel is skipping
over these stop states ?

Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>

>  		if ((state->flags & OPAL_PM_TIMEBASE_STOP) &&
>  		     (pnv_first_tb_loss_level > psscr_rl))
>  			pnv_first_tb_loss_level = psscr_rl;

--
Thanks and Regards
gautham.