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Message-ID: <5538DE7E.1020805@linux.vnet.ibm.com>
Date: Thu, 23 Apr 2015 17:28:54 +0530
From: Preeti U Murthy <preeti@...ux.vnet.ibm.com>
To: Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>,
linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org
CC: "Rafael J. Wysocki" <rjw@...ysocki.net>,
Viresh Kumar <viresh.kumar@...aro.org>,
linux-pm@...r.kernel.org
Subject: Re: [PATCH 2/2] cpufreq: powernv: Register for OCC related opal_message
notification
Hi Shilpa,
On 04/22/2015 10:34 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 it 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 <shilpa.bhat@...ux.vnet.ibm.com>
> CC: "Rafael J. Wysocki" <rjw@...ysocki.net>
> CC: Viresh Kumar <viresh.kumar@...aro.org>
> CC: linux-pm@...r.kernel.org
> ---
> drivers/cpufreq/powernv-cpufreq.c | 70 ++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 69 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
> index ebef0d8..5718765 100644
> --- a/drivers/cpufreq/powernv-cpufreq.c
> +++ b/drivers/cpufreq/powernv-cpufreq.c
> @@ -32,6 +32,7 @@
> #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)
> @@ -40,7 +41,7 @@
> #define PMSR_LP(x) ((x >> 48) & 0xFF)
>
> static struct cpufreq_frequency_table powernv_freqs[POWERNV_MAX_PSTATES+1];
> -static bool rebooting, throttled;
> +static bool rebooting, throttled, occ_reset;
>
> /*
> * Note: The set of pstates consists of contiguous integers, the
> @@ -395,6 +396,72 @@ static struct notifier_block powernv_cpufreq_reboot_nb = {
> .notifier_call = powernv_cpufreq_reboot_notifier,
> };
>
> +static char throttle_reason[6][50] = { "No throttling",
> + "Power Cap",
> + "Processor Over Temperature",
> + "Power Supply Failure",
> + "OverCurrent",
> + "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 0:
> + 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 in Reset\n");
> + break;
> + case 1:
> + pr_info("OCC is Loaded\n");
> + break;
> + case 2:
You may want to replace the numbers with macros. Like
OCC_RESET,OCC_LOAD, OCC_THROTTLE for better readability.
> + 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 is Active\n");
> + /* Sanity check for static governors */
> + powernv_cpufreq_throttle_check(smp_processor_id());
> + } else if (reason) {
> + throttled = true;
> + pr_info("Pmax reduced due to %s on chip %x\n",
> + throttle_reason[reason], (int)chip_id);
> + } else {
> + throttled = false;
> + pr_info("%s on chip %x\n",
> + throttle_reason[reason], (int)chip_id);
Don't you need a powernv_cpufreq_throttle_check() here? Or is it ok to
rely on the OCC notification for unthrottle ?
Regards
Preeti U Murthy
> + }
> + break;
> + }
> + 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;
> @@ -430,6 +497,7 @@ static int __init powernv_cpufreq_init(void)
> }
>
> 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);
>
--
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