From: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
To: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>,
vkoul@kernel.org
Cc: sanyog.r.kale@intel.com, yung-chuan.liao@linux.intel.com,
linux-kernel@vger.kernel.org, alsa-devel@alsa-project.org
Subject: Re: [PATCH 2/3] soundwire: qcom: add auto enumeration support
Date: Fri, 5 Mar 2021 10:39:50 +0000 [thread overview]
Message-ID: <5b067c8d-0d90-1531-a1b1-118fa73c0078@linaro.org> (raw)
In-Reply-To: <c5fe182d-1769-73ed-0268-5353fd030521@linux.intel.com>
On 03/03/2021 16:35, Pierre-Louis Bossart wrote:
>
>
> On 3/3/21 3:38 AM, Srinivas Kandagatla wrote:
>>
>>
>> On 02/03/2021 14:34, Pierre-Louis Bossart wrote:
>>>
>>>
>>>>>> + if (!val1 && !val2)
>>>>>> + break;
>>>>>> +
>>>>>> + addr = buf2[1] | (buf2[0] << 8) | (buf1[3] << 16) |
>>>>>> + ((u64)buf1[2] << 24) | ((u64)buf1[1] << 32) |
>>>>>> + ((u64)buf1[0] << 40);
>>>>>> +
>>>>>> + sdw_extract_slave_id(bus, addr, &id);
>>>>>> + /* Now compare with entries */
>>>>>> + list_for_each_entry_safe(slave, _s, &bus->slaves, node) {
>>>>>> + if (sdw_compare_devid(slave, id) == 0) {
>>>>>> + u32 status = qcom_swrm_get_n_device_status(ctrl, i);
>>>>>> + if (status == SDW_SLAVE_ATTACHED) {
>>>>>> + slave->dev_num = i;
>>>>>> + mutex_lock(&bus->bus_lock);
>>>>>> + set_bit(i, bus->assigned);
>>>>>> + mutex_unlock(&bus->bus_lock);
>>>>>> +
>>>>>> + }
>>>>>
>>>>> And that part is strange as well. The bus->assigned bit should be
>>>>> set even if the Slave is not in the list provided by platform
>>>>> firmware. It's really tracking the state of the hardware, and it
>>>>> should not be influenced by what software knows to manage.
>>>>
>>>> Am not 100% sure If I understand the concern here, but In normal
>>>> (non auto enum) cases this bit is set by the bus code while its
>>>> doing enumeration to assign a dev number from the assigned bitmap!
>>>>
>>>> However in this case where auto enumeration happens it makes sense
>>>> to set this here with matching dev number!
>>>>
>>>> AFAIU from code, each bit in this bitmap corresponds to slave dev
>>>> number!
>>>
>>> Yes, but the point was "why do you compare with information coming
>>> from platform firmware"? if the hardware reports the presence of
>>> devices on
>>
>> This is the logic that hardware IP document suggests to use to get get
>> the correct the device number associated with the slave!
>>
>>
>>> the link, why not use the information as is?
>>>
>>> You recently added code that helps us deal with devices that are not
>>> listed in DT or ACPI tables, so why would we filter in this specific
>>> loop?
>
> I don't think my point was understood, so let me try to explain it
> differently.
>
> it's my understanding that the hardware reads the DevID registers and
> writes a Device Number - so that the entire enumeration sequence started
> by reading DevID0 and finished by a successful write to SCP_DevNum is
> handled in hardware.
>
> The question is: what happens if that device is NOT described in the
> Device Tree data? The loop over bus->slaves will not find this device by
> comparing with known devID values, so the set_bit(i, bus->assigned) will
> not happen.
yes, that is true, There is no way we can assign a dev_number to the
device which is not enumerated on the bus!
Am sure this is the same behavior with soundwire core too, atleast form
the code I can see it sets the assigned bit for only the devices that
are enumerated on the bus! Not all the devices specified in DT!
Unless I missed something!
--srini
--srini
>
>
next prev parent reply other threads:[~2021-03-05 10:40 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-26 17:02 [PATCH 0/3] soundwire: qcom: add Clock Stop and Auto Enumeration support Srinivas Kandagatla
2021-02-26 17:02 ` [PATCH 1/3] soundwire: export sdw_compare_devid() and sdw_extract_slave_id() Srinivas Kandagatla
2021-02-26 17:02 ` [PATCH 2/3] soundwire: qcom: add auto enumeration support Srinivas Kandagatla
2021-02-26 17:44 ` Pierre-Louis Bossart
2021-03-02 10:33 ` Srinivas Kandagatla
2021-03-02 14:34 ` Pierre-Louis Bossart
2021-03-03 9:38 ` Srinivas Kandagatla
2021-03-03 16:35 ` Pierre-Louis Bossart
2021-03-05 10:39 ` Srinivas Kandagatla [this message]
2021-03-05 16:19 ` Pierre-Louis Bossart
2021-03-05 16:57 ` Srinivas Kandagatla
2021-02-26 17:02 ` [PATCH 3/3] soundwire: qcom: add clock stop via runtime pm support Srinivas Kandagatla
2021-02-26 17:41 ` Pierre-Louis Bossart
2021-03-03 11:46 ` Srinivas Kandagatla
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