lkml.org 
[lkml]   [2010]   [Jan]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] pm_qos: Add QoS param, minimum system bus frequency
On Thu, Dec 31, 2009 at 05:20:27PM -0800, Daniel Walker wrote:
> From: Praveen Chidambaram <pchidamb@quicinc.com>
>
> In some systems, the system bus speed can be varied, usually
> based on the current CPU frequency. However, various device
> drivers and/or applications may need a faster system bus for I/O
> even though the CPU itself may be idle

What happened to the discussion around multiple platforms needing
multiple bus pm_qos_requirements?

Is system bus freq too generic? (I'm worried about the name space)
Is this ok? (I'm asking linux-pm for input here.)
On X86 would this be analogous to FSB, Memory, or PCI bus frequencies?
What will happen when there are two buses each wanting a PM_QOS
parameter? Is that a likely scenario?

Also, on your platform you have a throttling driver controlling the
frequency of some bus, that will use this value as a constraint on how
far it will throttle. no? I would be interested in seeing this driver
sometime. (I just want to make sure no one bastardizes pm_qos into an
operating point thing. I'm not sure I can justify why but I want to
avoid that.)

Lets have a on list discussion around the above. Other than these I
don't see a problem with your patch. I would like to know that other Si
vendors have a need for it other than just yours and the
abstraction/naming is compatible to them as well.

--mgross
>
> Signed-off-by: Praveen Chidambaram <pchidamb@quicinc.com>
> Signed-off-by: David Brown <davidb@quicinc.com>
> Signed-off-by: Daniel Walker <dwalker@codeaurora.org>
> ---
> include/linux/pm_qos_params.h | 3 ++-
> kernel/pm_qos_params.c | 32 +++++++++++++++++++++++++-------
> 2 files changed, 27 insertions(+), 8 deletions(-)
>
> diff --git a/include/linux/pm_qos_params.h b/include/linux/pm_qos_params.h
> index d74f75e..091c13c 100644
> --- a/include/linux/pm_qos_params.h
> +++ b/include/linux/pm_qos_params.h
> @@ -10,8 +10,9 @@
> #define PM_QOS_CPU_DMA_LATENCY 1
> #define PM_QOS_NETWORK_LATENCY 2
> #define PM_QOS_NETWORK_THROUGHPUT 3
> +#define PM_QOS_SYSTEM_BUS_FREQ 4
>
> -#define PM_QOS_NUM_CLASSES 4
> +#define PM_QOS_NUM_CLASSES 5
> #define PM_QOS_DEFAULT_VALUE -1
>
> int pm_qos_add_requirement(int qos, char *name, s32 value);
> diff --git a/kernel/pm_qos_params.c b/kernel/pm_qos_params.c
> index 3db49b9..8576f40 100644
> --- a/kernel/pm_qos_params.c
> +++ b/kernel/pm_qos_params.c
> @@ -102,12 +102,24 @@ static struct pm_qos_object network_throughput_pm_qos = {
> .comparitor = max_compare
> };
>
> +static BLOCKING_NOTIFIER_HEAD(system_bus_freq_notifier);
> +static struct pm_qos_object system_bus_freq_pm_qos = {
> + .requirements =
> + {LIST_HEAD_INIT(system_bus_freq_pm_qos.requirements.list)},
> + .notifiers = &system_bus_freq_notifier,
> + .name = "system_bus_freq",
> + .default_value = 0,
> + .target_value = ATOMIC_INIT(0),
> + .comparitor = max_compare
> +};
> +
>
> -static struct pm_qos_object *pm_qos_array[] = {
> - &null_pm_qos,
> - &cpu_dma_pm_qos,
> - &network_lat_pm_qos,
> - &network_throughput_pm_qos
> +static struct pm_qos_object *pm_qos_array[PM_QOS_NUM_CLASSES] = {
> + [PM_QOS_RESERVED] = &null_pm_qos,
> + [PM_QOS_CPU_DMA_LATENCY] = &cpu_dma_pm_qos,
> + [PM_QOS_NETWORK_LATENCY] = &network_lat_pm_qos,
> + [PM_QOS_NETWORK_THROUGHPUT] = &network_throughput_pm_qos,
> + [PM_QOS_SYSTEM_BUS_FREQ] = &system_bus_freq_pm_qos,

I've never used or seen this syntax before. Is it C99? FWIW I like it.

> };
>
> static DEFINE_SPINLOCK(pm_qos_lock);
> @@ -313,7 +325,7 @@ EXPORT_SYMBOL_GPL(pm_qos_remove_requirement);
> * will register the notifier into a notification chain that gets called
> * upon changes to the pm_qos_class target value.
> */
> - int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
> +int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
> {
> int retval;
>
> @@ -409,9 +421,15 @@ static int __init pm_qos_power_init(void)
> return ret;
> }
> ret = register_pm_qos_misc(&network_throughput_pm_qos);
> - if (ret < 0)
> + if (ret < 0) {
> printk(KERN_ERR
> "pm_qos_param: network_throughput setup failed\n");
> + return ret;
> + }
> + ret = register_pm_qos_misc(&system_bus_freq_pm_qos);
> + if (ret < 0)
> + printk(KERN_ERR
> + "pm_qos_param: system_bus_freq setup failed\n");
>
> return ret;
> }
> --
> 1.6.3.3


\
 
 \ /
  Last update: 2010-01-04 22:41    [from the cache]
©2003-2011 Jasper Spaans