From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
To: Vinod Koul <vkoul@kernel.org>
Cc: alsa-devel@alsa-project.org, tiwai@suse.de,
gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
ranjani.sridharan@linux.intel.com, hui.wang@canonical.com,
broonie@kernel.org, srinivas.kandagatla@linaro.org,
jank@cadence.com, mengdong.lin@intel.com,
slawomir.blauciak@intel.com, sanyog.r.kale@intel.com,
Bard Liao <yung-chuan.liao@linux.intel.com>,
rander.wang@linux.intel.com, bard.liao@intel.com
Subject: Re: [PATCH 8/9] soundwire: intel: add wake interrupt support
Date: Wed, 15 Jul 2020 09:22:31 -0500 [thread overview]
Message-ID: <2832a0d0-dd19-9532-2c6e-814b796b4e20@linux.intel.com> (raw)
In-Reply-To: <20200715045011.GO34333@vkoul-mobl>
On 7/14/20 11:50 PM, Vinod Koul wrote:
> On 01-07-20, 10:25, Pierre-Louis Bossart wrote:
>>
>>>>>> + * wake up master and slave so that slave can notify master
>>>>>> + * the wakeen event and let codec driver check codec status
>>>>>> + */
>>>>>> + list_for_each_entry(slave, &bus->slaves, node) {
>>>>>> + /*
>>>>>> + * discard devices that are defined in ACPI tables but
>>>>>> + * not physically present and devices that cannot
>>>>>> + * generate wakes
>>>>>> + */
>>>>>> + if (slave->dev_num_sticky && slave->prop.wake_capable)
>>>>>> + pm_request_resume(&slave->dev);
>>>>>
>>>>> Hmmm, shouldn't slave do this? would it not make sense to notify the
>>>>> slave thru callback and then slave decides to resume or not..?
>>>>
>>>> In this mode, the bus is clock-stop mode, and events are detected with level
>>>> detector tied to PCI events. The master and slave devices are all in
>>>> pm_runtime suspended states. The codec cannot make any decisions on its own
>>>> since the bus is stopped, it needs to first resume, which assumes that the
>>>> master resumes first and the enumeration re-done before it can access any of
>>>> its registers.
>>>>
>>>> By looping through the list of devices that can generate events, you end-up
>>>> first forcing the master to resume, and then each slave resumes and can
>>>> check who generated the event and what happened while suspended. if the
>>>> codec didn't generate the event it will go back to suspended mode after the
>>>> usual timeout.
>>>>
>>>> We can add a callback but that callback would only be used for Intel
>>>> solutions, but internally it would only do a pm_request_resume() since the
>>>> codec cannot make any decisions before first resuming. In other words, it
>>>> would be an Intel-specific callback that is implemented using generic resume
>>>> operations. It's probably better to keep this in Intel-specific code, no?
>>>
>>> I do not like the idea that a device would be woken up, that kind of
>>> defeats the whole idea behind the runtime pm. Waking up a device to
>>> check the events is a generic sdw concept, I don't see that as Intel
>>> specific one.
>>
>> In this case, this in an Intel-specific mode that's beyond what MIPI
>> defined. This is not the traditional in-band SoundWire wake defined in the
>> SoundWire specification. The bus is completely down, the master IP is
>> powered-off and all context lost. There is still the ability for a Slave
>> device to throw a wake as defined by MIPI in clock-stop-mode1, but this is
>> handled with a separate level detector and the wake detection is handled by
>> the PCI subsystem. On a wake, the master IP needs to be powered-up, the
>> entire bus needs to be restarted and the Slave devices re-enumerated.
>
> Right and I would expect that Slave device would do runtime_get_sync()
> first thing in the callback. That would ensure that the Master is
> powered up, Slave is powered up, all enumeration is complete. This is
> more standard way to deal with this, we expect devices to be so we
> low powered or off so cannot do read/write unless we resume.
As shared privately with you, we don't need to deal with device PM or
add a callback, it's enough to resume the master, which will indirectly
restart the bus and result in devices being resumed when they report
their interrupt status. We'll share the update from [1] in the v2.
[1] https://github.com/thesofproject/linux/pull/2247
next prev parent reply other threads:[~2020-07-15 14:23 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-23 17:35 [PATCH 0/9] soundwire: intel: revisit SHIM programming Bard Liao
2020-06-23 17:35 ` [PATCH 1/9] soundwire: intel: reuse code for wait loops to set/clear bits Bard Liao
2020-06-23 17:35 ` [PATCH 2/9] soundwire: intel: revisit SHIM programming sequences Bard Liao
2020-06-23 17:35 ` [PATCH 3/9] soundwire: intel: introduce a helper to arm link synchronization Bard Liao
2020-06-23 17:35 ` [PATCH 4/9] soundwire: intel: introduce helper for " Bard Liao
2020-06-23 17:35 ` [PATCH 5/9] soundwire: intel_init: add implementation of sdw_intel_enable_irq() Bard Liao
2020-06-23 17:35 ` [PATCH 6/9] soundwire: intel_init: use EXPORT_SYMBOL_NS Bard Liao
2020-06-23 17:35 ` [PATCH 7/9] soundwire: intel/cadence: merge Soundwire interrupt handlers/threads Bard Liao
2020-06-30 16:24 ` Vinod Koul
2020-06-30 16:46 ` Pierre-Louis Bossart
2020-07-01 5:42 ` Vinod Koul
2020-07-02 7:35 ` Liao, Bard
2020-07-02 15:01 ` Pierre-Louis Bossart
2020-07-15 4:54 ` Vinod Koul
2020-07-15 14:11 ` Pierre-Louis Bossart
2020-06-23 17:35 ` [PATCH 8/9] soundwire: intel: add wake interrupt support Bard Liao
2020-06-30 16:51 ` Vinod Koul
2020-06-30 17:18 ` Pierre-Louis Bossart
2020-07-01 5:56 ` Vinod Koul
2020-07-01 15:25 ` Pierre-Louis Bossart
2020-07-15 4:50 ` Vinod Koul
2020-07-15 14:22 ` Pierre-Louis Bossart [this message]
2020-06-23 17:35 ` [PATCH 9/9] Soundwire: intel_init: save Slave(s) _ADR info in sdw_intel_ctx Bard Liao
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