Subject: Re: [PATCH v3 3/6] cpufreq: powernv: Register for OCC related opal_message notification

From: Preeti U Murthy <[email-masked]>
Date: Tue, 05 May 2015 09:12:58 +0530

On 05/04/2015 02:24 PM, Shilpasri G Bhat wrote:
> OCC is an On-Chip-Controller which takes care of power and thermal
> safety of the chip. During runtime due to power failure or
> overtemperature the OCC may throttle the frequencies of the CPUs to
> remain within the power budget.
> 
> We want the cpufreq driver to be aware of such situations to be able
> to report the reason to the user. We register to opal_message_notifier
> to receive OCC messages from opal.
> 
> powernv_cpufreq_throttle_check() reports any frequency throttling and
> this patch will report the reason or event that caused throttling. We
> can be throttled if OCC is reset or OCC limits Pmax due to power or
> thermal reasons. We are also notified of unthrottling after an OCC
> reset or if OCC restores Pmax on the chip.
> 
> Signed-off-by: Shilpasri G Bhat <[email-masked]>
> ---
> Changes from v2:
> - Patch split in to multiple patches.
> - This patch contains only the opal_message notification handler
> 
> Changes from v1:
> - Add macros to define OCC_RESET, OCC_LOAD and OCC_THROTTLE
> - Define a structure to store chip id, chip mask which has bits set
>   for cpus present in the chip, throttled state and a work_struct.
> - Modify powernv_cpufreq_throttle_check() to be called via smp_call()
> - On Pmax throttling/unthrottling update 'chip.throttled' and not the
>   global 'throttled' as Pmax capping is local to the chip.
> - Remove the condition which checks if local pstate is less than Pmin
>   while checking for Psafe frequency. When OCC becomes active after
>   reset we update 'thottled' to false and when the cpufreq governor
>   initiates a pstate change, the local pstate will be in Psafe and we
>   will be reporting a false positive when we are not throttled.
> - Schedule a kworker on receiving throttling/unthrottling OCC message
>   for that chip and schedule on all chips after receiving active.
> - After an OCC reset all the cpus will be in Psafe frequency. So call
>   target() and restore the frequency to policy->cur after OCC_ACTIVE
>   and Pmax unthrottling
> - Taken care of Viresh and Preeti's comments.
> 
>  drivers/cpufreq/powernv-cpufreq.c | 75 ++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 74 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
> index d0c18c9..9268424 100644
> --- a/drivers/cpufreq/powernv-cpufreq.c
> +++ b/drivers/cpufreq/powernv-cpufreq.c
> @@ -33,15 +33,19 @@
>  #include <asm/firmware.h>
>  #include <asm/reg.h>
>  #include <asm/smp.h> /* Required for cpu_sibling_mask() in UP configs */
> +#include <asm/opal.h>
> 
>  #define POWERNV_MAX_PSTATES	256
>  #define PMSR_PSAFE_ENABLE	(1UL << 30)
>  #define PMSR_SPR_EM_DISABLE	(1UL << 31)
>  #define PMSR_MAX(x)		((x >> 32) & 0xFF)
>  #define PMSR_LP(x)		((x >> 48) & 0xFF)
> +#define OCC_RESET		0
> +#define OCC_LOAD		1
> +#define OCC_THROTTLE		2
> 
>  static struct cpufreq_frequency_table powernv_freqs[POWERNV_MAX_PSTATES+1];
> -static bool rebooting, throttled;
> +static bool rebooting, throttled, occ_reset;
> 
>  static struct chip {
>  	unsigned int id;
> @@ -414,6 +418,74 @@ static struct notifier_block powernv_cpufreq_reboot_nb = {
>  	.notifier_call = powernv_cpufreq_reboot_notifier,
>  };
> 
> +static char throttle_reason[][30] = {
> +					"No throttling",
> +					"Power Cap",
> +					"Processor Over Temperature",
> +					"Power Supply Failure",
> +					"Over Current",
> +					"OCC Reset"
> +				     };
> +
> +static int powernv_cpufreq_occ_msg(struct notifier_block *nb,
> +				   unsigned long msg_type, void *msg)
> +{
> +	struct opal_msg *occ_msg = msg;
> +	uint64_t token;
> +	uint64_t chip_id, reason;
> +
> +	if (msg_type != OPAL_MSG_OCC)
> +		return 0;
> +
> +	token = be64_to_cpu(occ_msg->params[0]);
> +
> +	switch (token) {
> +	case OCC_RESET:
> +		occ_reset = true;
> +		/*
> +		 * powernv_cpufreq_throttle_check() is called in
> +		 * target() callback which can detect the throttle state
> +		 * for governors like ondemand.
> +		 * But static governors will not call target() often thus
> +		 * report throttling here.
> +		 */
> +		if (!throttled) {
> +			throttled = true;
> +			pr_crit("CPU Frequency is throttled\n");
> +		}
> +		pr_info("OCC: Reset\n");
> +		break;
> +	case OCC_LOAD:
> +		pr_info("OCC: Loaded\n");
> +		break;
> +	case OCC_THROTTLE:
> +		chip_id = be64_to_cpu(occ_msg->params[1]);
> +		reason = be64_to_cpu(occ_msg->params[2]);
> +
> +		if (occ_reset) {
> +			occ_reset = false;
> +			throttled = false;
> +			pr_info("OCC: Active\n");
> +			return 0;
> +		}
> +
> +		if (reason && reason <= 5)
> +			pr_info("OCC: Chip %u Pmax reduced due to %s\n",
> +				(unsigned int)chip_id,
> +				throttle_reason[reason]);
> +		else if (!reason)
> +			pr_info("OCC: Chip %u %s\n", (unsigned int)chip_id,
> +				throttle_reason[reason]);
> +	}
> +	return 0;
> +}
> +
> +static struct notifier_block powernv_cpufreq_opal_nb = {
> +	.notifier_call	= powernv_cpufreq_occ_msg,
> +	.next		= NULL,
> +	.priority	= 0,
> +};
> +
>  static void powernv_cpufreq_stop_cpu(struct cpufreq_policy *policy)
>  {
>  	struct powernv_smp_call_data freq_data;
> @@ -481,6 +553,7 @@ static int __init powernv_cpufreq_init(void)
>  		return rc;
> 
>  	register_reboot_notifier(&powernv_cpufreq_reboot_nb);
> +	opal_message_notifier_register(OPAL_MSG_OCC, &powernv_cpufreq_opal_nb);
>  	return cpufreq_register_driver(&powernv_cpufreq_driver);
>  }
>  module_init(powernv_cpufreq_init);
> 

Looks good.

Reviewed-by: Preeti U Murthy <[email-masked]>