linux-kernel - Re: [PATCH 3/5] powernv:idle: Define idle init function for power8

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Message-ID: <20170707010646.0157d251@roar.ozlabs.ibm.com>
Date:   Fri, 7 Jul 2017 01:06:46 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Michael Neuling <mikey@...ling.org>,
        Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
        Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Akshay Adiga <akshay.adiga@...ux.vnet.ibm.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH 3/5] powernv:idle: Define idle init function for power8

On Wed,  5 Jul 2017 22:08:14 +0530
"Gautham R. Shenoy" <ego@...ux.vnet.ibm.com> wrote:

> From: "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
> 
> In this patch we define a new function named pnv_power8_idle_init().
> 
> We move the following code from pnv_init_idle_states() into this newly
> defined function.
>    a) That patches out pnv_fastsleep_workaround_at_entry/exit when
>       no states with OPAL_PM_SLEEP_ENABLED_ER1 are present.
>    b) Creating a sysfs control to choose how the workaround has to be
>    applied when a OPAL_PM_SLEEP_ENABLED_ER1 state is present.
>    c) Set ppc_md.power_save to power7_idle when OPAL_PM_NAP_ENABLED is
>    present.
> 
> With this, all the power8 specific initializations are in one place.
> 
> Signed-off-by: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>
> ---
>  arch/powerpc/platforms/powernv/idle.c | 59 ++++++++++++++++++++++++-----------
>  1 file changed, 40 insertions(+), 19 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
> index a5990d9..c400ff9 100644
> --- a/arch/powerpc/platforms/powernv/idle.c
> +++ b/arch/powerpc/platforms/powernv/idle.c
> @@ -564,6 +564,44 @@ static void __init pnv_power9_idle_init(void)
>  		pnv_first_deep_stop_state);
>  }
>  
> +
> +static void __init pnv_power8_idle_init(void)
> +{
> +	int i;
> +	bool has_nap = false;
> +	bool has_sleep_er1 = false;
> +	int dt_idle_states = pnv_idle.nr_states;
> +
> +	for (i = 0; i < dt_idle_states; i++) {
> +		struct pnv_idle_state *state = &pnv_idle.states[i];
> +
> +		if (state->flags & OPAL_PM_NAP_ENABLED)
> +			has_nap = true;
> +		if (state->flags & OPAL_PM_SLEEP_ENABLED_ER1)
> +			has_sleep_er1 = true;
> +	}
> +
> +	if (!has_sleep_er1) {
> +		patch_instruction(
> +			(unsigned int *)pnv_fastsleep_workaround_at_entry,
> +			PPC_INST_NOP);
> +		patch_instruction(
> +			(unsigned int *)pnv_fastsleep_workaround_at_exit,
> +			PPC_INST_NOP);
> +	} else {
> +		/*
> +		 * OPAL_PM_SLEEP_ENABLED_ER1 is set. It indicates that
> +		 * workaround is needed to use fastsleep. Provide sysfs
> +		 * control to choose how this workaround has to be applied.
> +		 */
> +		device_create_file(cpu_subsys.dev_root,
> +				&dev_attr_fastsleep_workaround_applyonce);
> +	}
> +
> +	if (has_nap)
> +		ppc_md.power_save = power7_idle;
> +}
> +
>  /*
>   * Returns 0 if prop1_len == prop2_len. Else returns -1
>   */
> @@ -837,6 +875,8 @@ static int __init pnv_probe_idle_states(void)
>  
>  	if (cpu_has_feature(CPU_FTR_ARCH_300))
>  		pnv_power9_idle_init();
> +	else
> +		pnv_power8_idle_init();
>  
>  	for (i = 0; i < dt_idle_states; i++) {
>  		if (!pnv_idle.states[i].valid)
> @@ -858,22 +898,6 @@ static int __init pnv_init_idle_states(void)
>  	if (pnv_probe_idle_states())
>  		goto out;
>  
> -	if (!(supported_cpuidle_states & OPAL_PM_SLEEP_ENABLED_ER1)) {
> -		patch_instruction(
> -			(unsigned int *)pnv_fastsleep_workaround_at_entry,
> -			PPC_INST_NOP);
> -		patch_instruction(
> -			(unsigned int *)pnv_fastsleep_workaround_at_exit,
> -			PPC_INST_NOP);

So previously this would run on POWER9 and patch out those branches.
But POWER9 never runs that code, so no problem. Good cleanup.

Reviewed-by: Nicholas Piggin <npiggin@...il.com>