linux-kernel - Re: [RFC] ath9k: Fix ath9k prevents CPU to enter C3 states

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Message-ID: <4D53F3A0.6050900@atheros.com>
Date:	Thu, 10 Feb 2011 19:48:08 +0530
From:	Mohammed Shafi <mshajakhan@...eros.com>
To:	Luis Rodriguez <Luis.Rodriguez@...eros.com>
CC:	Mohammed Shajakhan <Mohammed.Shajakhan@...eros.com>,
	"linville@...driver.com" <linville@...driver.com>,
	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Tim Gardner <tim.gardner@...onical.com>,
	Mark Gross <mgross@...ux.intel.com>,
	Senthilkumar Balasubramanian 
	<Senthilkumar.Balasubramanian@...eros.com>
Subject: Re: [RFC] ath9k: Fix ath9k prevents CPU to enter C3 states

On Thursday 10 February 2011 01:28 AM, Luis Rodriguez wrote:
> On Wed, Feb 09, 2011 at 06:33:27AM -0800, Mohammed Shajakhan wrote:
>    
>> From: Mohammed Shafi Shajakhan<mshajakhan@...eros.com>
>>
>> The DMA latency issue is observed only in Intel pinetrail platforms but
>> in the driver we had a default PM-QOS value of 55. This caused
>> unnecessary power consumption and battery drain in other platforms.
>> Address this issue by disabling PM-QOS by default by setting it's value
>> as '0' and making code changes appropriately.This addresses the bug:
>> https://bugzilla.kernel.org/show_bug.cgi?id=27532
>> 	If the user sees some DMA latency issue he can still use the pmqos as a
>> module parameter to trade power for throughput as below:
>> sudo modprobe ath9k pmqos=55
>>      
> How many times are we going to write some work around for some
> platform unpatched BIOS bug ?
>
> mcgrof@tux ~/wireless-testing (git::master)$ git grep pm_qos_update_request drivers/
> drivers/net/e1000e/netdev.c:                    pm_qos_update_request(&adapter->netdev->pm_qos_req, 55);
> drivers/net/e1000e/netdev.c:                    pm_qos_update_request(&adapter->netdev->pm_qos_req,
> drivers/net/wireless/ath/ath9k/main.c:  pm_qos_update_request(&sc->pm_qos_req, ath9k_pm_qos_value);
> drivers/net/wireless/ath/ath9k/main.c:  pm_qos_update_request(&sc->pm_qos_req, PM_QOS_DEFAULT_VALUE);
> drivers/net/wireless/ipw2x00/ipw2100.c: pm_qos_update_request(&ipw2100_pm_qos_req, 175);
> drivers/net/wireless/ipw2x00/ipw2100.c: pm_qos_update_request(&ipw2100_pm_qos_req, PM_QOS_DEFAULT_VALUE);
>
> Can't we punt this crap to userspace?
>    
Luis thanks for the script and sorry I missed it in the bugzilla. Luis I 
agree these workarounds are better placed to be in user place and the 
only thing is those have issues must be aware of the script.
I am ccing Senthil to have his views.

thanks,
shafi
> http://www.kernel.org/pub/linux/kernel/people/mcgrof/scripts/cpudmalatency.c
>
> Can distributions just autodetect this issue and call something like this?
>
>    Luis
>
>    
>> Signed-off-by: Mohammed Shafi Shajakhan<mshajakhan@...eros.com>
>> ---
>>   drivers/net/wireless/ath/ath9k/ath9k.h |    4 +++-
>>   drivers/net/wireless/ath/ath9k/init.c  |    9 +++++----
>>   drivers/net/wireless/ath/ath9k/main.c  |    9 +++++----
>>   3 files changed, 13 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/net/wireless/ath/ath9k/ath9k.h b/drivers/net/wireless/ath/ath9k/ath9k.h
>> index 9272278..55fcd01 100644
>> --- a/drivers/net/wireless/ath/ath9k/ath9k.h
>> +++ b/drivers/net/wireless/ath/ath9k/ath9k.h
>> @@ -57,7 +57,9 @@ struct ath_node;
>>
>>   #define A_MAX(a, b) ((a)>  (b) ? (a) : (b))
>>
>> -#define ATH9K_PM_QOS_DEFAULT_VALUE	55
>> +/* By default PM QOS is disabled */
>> +#define ATH9K_PM_QOS_DEFAULT_VALUE	0
>> +
>>
>>   #define TSF_TO_TU(_h,_l) \
>>   	((((u32)(_h))<<  22) | (((u32)(_l))>>  10))
>> diff --git a/drivers/net/wireless/ath/ath9k/init.c b/drivers/net/wireless/ath/ath9k/init.c
>> index e5c1eea..658ea02 100644
>> --- a/drivers/net/wireless/ath/ath9k/init.c
>> +++ b/drivers/net/wireless/ath/ath9k/init.c
>> @@ -43,7 +43,7 @@ MODULE_PARM_DESC(btcoex_enable, "Enable wifi-BT coexistence");
>>
>>   int ath9k_pm_qos_value = ATH9K_PM_QOS_DEFAULT_VALUE;
>>   module_param_named(pmqos, ath9k_pm_qos_value, int, S_IRUSR | S_IRGRP | S_IROTH);
>> -MODULE_PARM_DESC(pmqos, "User specified PM-QOS value");
>> +MODULE_PARM_DESC(pmqos, "User specified PM-QOS value, by default disabled");
>>
>>   bool is_ath9k_unloaded;
>>   /* We use the hw_value as an index into our private channel structure */
>> @@ -759,8 +759,8 @@ int ath9k_init_device(u16 devid, struct ath_softc *sc, u16 subsysid,
>>
>>   	ath_init_leds(sc);
>>   	ath_start_rfkill_poll(sc);
>> -
>> -	pm_qos_add_request(&sc->pm_qos_req, PM_QOS_CPU_DMA_LATENCY,
>> +	if (ath9k_pm_qos_value)
>> +		pm_qos_add_request(&sc->pm_qos_req, PM_QOS_CPU_DMA_LATENCY,
>>   			   PM_QOS_DEFAULT_VALUE);
>>
>>   	return 0;
>> @@ -819,7 +819,8 @@ void ath9k_deinit_device(struct ath_softc *sc)
>>   	ath9k_ps_restore(sc);
>>
>>   	ieee80211_unregister_hw(hw);
>> -	pm_qos_remove_request(&sc->pm_qos_req);
>> +	if (ath9k_pm_qos_value)
>> +		pm_qos_remove_request(&sc->pm_qos_req);
>>   	ath_rx_cleanup(sc);
>>   	ath_tx_cleanup(sc);
>>   	ath9k_deinit_softc(sc);
>> diff --git a/drivers/net/wireless/ath/ath9k/main.c b/drivers/net/wireless/ath/ath9k/main.c
>> index 4ed43b2..3855092 100644
>> --- a/drivers/net/wireless/ath/ath9k/main.c
>> +++ b/drivers/net/wireless/ath/ath9k/main.c
>> @@ -1119,9 +1119,10 @@ static int ath9k_start(struct ieee80211_hw *hw)
>>
>>   	/* User has the option to provide pm-qos value as a module
>>   	 * parameter rather than using the default value of
>> -	 * 'ATH9K_PM_QOS_DEFAULT_VALUE'.
>> +	 * 'ATH9K_PM_QOS_DEFAULT_VALUE' which disables PM QOS.
>>   	 */
>> -	pm_qos_update_request(&sc->pm_qos_req, ath9k_pm_qos_value);
>> +	if (ath9k_pm_qos_value)
>> +		pm_qos_update_request(&sc->pm_qos_req, ath9k_pm_qos_value);
>>
>>   	if (ah->caps.pcie_lcr_extsync_en&&  common->bus_ops->extn_synch_en)
>>   		common->bus_ops->extn_synch_en(common);
>> @@ -1266,8 +1267,8 @@ static void ath9k_stop(struct ieee80211_hw *hw)
>>   	ath_radio_disable(sc, hw);
>>
>>   	sc->sc_flags |= SC_OP_INVALID;
>> -
>> -	pm_qos_update_request(&sc->pm_qos_req, PM_QOS_DEFAULT_VALUE);
>> +	if (ath9k_pm_qos_value)
>> +		pm_qos_update_request(&sc->pm_qos_req, PM_QOS_DEFAULT_VALUE);
>>
>>   	mutex_unlock(&sc->mutex);
>>
>> -- 
>> 1.7.0.4
>>
>>      
> .
>
>    
--
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