From: Sagar Dharia <sdharia@codeaurora.org>
To: Mark Brown <broonie@kernel.org>
Cc: gregkh@linuxfoundation.org, bp@suse.de, poeschel@lemonage.de,
treding@nvidia.com, gong.chen@linux.intel.com,
andreas.noever@gmail.com, alan@linux.intel.com,
mathieu.poirier@linaro.org, daniel@ffwll.ch, oded.gabbay@amd.com,
jkosina@suse.cz, sharon.dvir1@mail.huji.ac.il, joe@perches.com,
davem@davemloft.net, james.hogan@imgtec.com,
michael.opdenacker@free-electrons.com,
daniel.thompson@linaro.org, robh+dt@kernel.org,
pawel.moll@arm.com, mark.rutland@arm.com,
ijc+devicetree@hellion.org.uk, galak@codeaurora.org,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
kheitke@audience.com, mlocke@codeaurora.org,
agross@codeaurora.org, linux-arm-msm@vger.kernel.org
Subject: Re: [PATCH V3 5/6] slimbus: Add support for 'clock-pause' feature
Date: Mon, 17 Aug 2015 17:43:01 -0600 [thread overview]
Message-ID: <55D27185.4000101@codeaurora.org> (raw)
In-Reply-To: <20150814183918.GF10748@sirena.org.uk>
Hi Mark,
On 8/14/2015 12:39 PM, Mark Brown wrote:
> On Mon, Aug 03, 2015 at 12:59:49AM -0600, Sagar Dharia wrote:
>
>> @@ -459,6 +459,8 @@ int slim_register_controller(struct slim_controller *ctrl)
>> mutex_init(&ctrl->m_ctrl);
>> spin_lock_init(&ctrl->tx.lock);
>> spin_lock_init(&ctrl->rx.lock);
>> + mutex_init(&ctrl->sched.m_reconf);
>> + init_completion(&ctrl->sched.pause_comp);
> Should there not be more interaction with the rest of the framework on
> clock pauses - the bus will need to be started to do transfers for
> example?
I'm relying on controller's pm_runtime as you pointed out for
entering/exiting clock-pause.
The reason to initiate clock-pause from controller was more on the lines
of clock-pause sequence being expensive, and tight coupling between
controller/framer-clocks and clock-pause.
Three reconfiguration-transfer-commands have to be broadcast on the
lines to enter clock-pause, and exiting it is needs 'wakeup' callback
for controller.
Doing this per transfer will be a big overhead.
Using pm_runtime's autosuspend feature allows the controller-device to
enter clock-pause after periods of inactivity to avoid thrashing.
As a trade-off, I am proposing that controller should initiate
clock-pause from its pm_runtime callbacks, and framework should provide
the means to do it.
Also, typically clocks of the controller are coupled with clock-pause
and clocks cannot be turned off until the clock-pause sequence is sent
on the bus since framer has to keep clocking the bus.
Thanks
Sagar
>
>> +#include <linux/slimbus.h>
>> +/**
> Missing blank line.
>
>> + * slim_ctrl_clk_pause: Called by slimbus controller to enter/exit 'clock pause'
> Is the controller the best place to initiate bus pausing? It's
> surprising to me that it would be, the bus being idle isn't something
> that needs controller specific knowledge so I'd expect the framework to
> have standard support for this.
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation
next prev parent reply other threads:[~2015-08-17 23:43 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-03 6:59 [PATCH V3 0/6] Introduce framework for SLIMbus device drivers Sagar Dharia
2015-08-03 6:59 ` [PATCH V3 1/6] SLIMbus: Device management on SLIMbus Sagar Dharia
2015-08-14 18:17 ` Mark Brown
2015-08-03 6:59 ` [PATCH V3 2/6] of/slimbus: OF helper for SLIMbus Sagar Dharia
2015-08-03 16:13 ` Rob Herring
2015-08-04 17:27 ` Mark Brown
2015-08-06 19:10 ` Sagar Dharia
2015-08-03 6:59 ` [PATCH V3 3/6] slimbus: Add messaging APIs to slimbus framework Sagar Dharia
2015-08-14 18:25 ` Mark Brown
2015-08-14 18:33 ` Mark Brown
2015-08-03 6:59 ` [PATCH V3 4/6] slim: qcom: Add Qualcomm Slimbus controller driver Sagar Dharia
2015-08-14 18:31 ` Mark Brown
[not found] ` <20150814183106.GE10748-GFdadSzt00ze9xe1eoZjHA@public.gmane.org>
2015-08-17 23:44 ` Sagar Dharia
2015-08-03 6:59 ` [PATCH V3 5/6] slimbus: Add support for 'clock-pause' feature Sagar Dharia
2015-08-14 18:39 ` Mark Brown
2015-08-17 23:43 ` Sagar Dharia [this message]
2015-08-03 6:59 ` [PATCH V3 6/6] slim: qcom: Add runtime-pm support using clock-pause feature Sagar Dharia
2015-08-14 18:43 ` Mark Brown
2015-08-14 18:46 ` [PATCH V3 0/6] Introduce framework for SLIMbus device drivers Mark Brown
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