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 5/6] soundwire: qcom: update register read/write routine
Date: Tue, 2 Feb 2021 10:19:46 +0000 [thread overview]
Message-ID: <4e3ebb99-5647-f71c-1256-a2c55bd9995f@linaro.org> (raw)
In-Reply-To: <b87758d0-5862-3b4e-5a90-7b27d0c78d0d@linux.intel.com>
On 01/02/2021 16:42, Pierre-Louis Bossart wrote:
>
>
> On 2/1/21 9:50 AM, Srinivas Kandagatla wrote:
>>
>>
>> On 29/01/2021 19:33, Pierre-Louis Bossart wrote:
>>>
>>>
>>> On 1/29/21 11:32 AM, Srinivas Kandagatla wrote:
>>>> In the existing code every soundwire register read and register write
>>>> are kinda blocked. Each of these are using a special command id that
>>>
>>> what does 'kinda blocked' mean?
>>
>> I meant read/writes are waiting for completion interrupt!
>>
>>>
>>>> generates interrupt after it successfully finishes. This is really
>>>> overhead, limiting and not really necessary unless we are doing
>>>> something special.
>>>>
>>>> We can simply read/write the fifo that should also give exactly
>>>> what we need! This will also allow to read/write registers in
>>>> interrupt context, which was not possible with the special
>>>> command approach.
>>>
>>> This is really unclear, sorry.
>>
>> If read/writes are waiting for an interrupt, it becomes difficult to
>> read or write to any registers from same interrupt handler!
>
> Well, yes, you need to handle the complete() at a lower level than the
> code that initiates the transactions otherwise you self-deadlock.
>
> IIRC in the Intel initial code, the complete was in the handler and the
> register IOs in the thread.
>
Yes, we did the same in previous version of the code, however with this
patch reading/writing fifo directly without need of completion should
remove that need of another thread!
>>
>>
>>>
>>>> + if (id != SWR_BROADCAST_CMD_ID) {
>>>> + if (id < 14)
>>>> + id += 1;
>>>> + else
>>>> + id = 0;
>>>
>>> that is really odd. if id=13 (group2) then id becomes 14 (master
>>> address). A comment is really needed here.
>>
>> This is magic value for each fifo read or write, so that we can verify
>> that them by comparing with this magic value!
>>
>> This has nothing to do with device number!
>
> You should probably add a comment here then, or use a #define instead of
> the 14 which threw me off.
I agree!
>
>>
>>>
>>>> + if (cmd_id == SWR_BROADCAST_CMD_ID) {
>>>> + /*
>>>> + * sleep for 10ms for MSM soundwire variant to allow broadcast
>>>> + * command to complete.
>>>
>>> that's also super-odd. There is nothing in SoundWire that makes any
>>> difference between a regular and a broadcast command. they all
>>> complete in the same time (a frame).
>>>> + */
>>>> + ret = wait_for_completion_timeout(&swrm->broadcast, (2 *
>>>> HZ/10));
>>>
>>> is this 10ms really or dependent on CONFIG_HZ?
>
> comment missed?
Not intentionally :-)
I should probably to use msecs_to_jiffies here to keep it inline with
the comment!
--srini
>
>>>
>>>> + if (!ret)
>>>> + ret = SDW_CMD_IGNORED;
>>>> + else
>>>> + ret = SDW_CMD_OK;
>>>
>>> no CMD_FAILED support?
>>
>> Qcom controllers does not provide that information if the command is
>> ignored or failed by any means!
>>
>> That was the behavior from the starting of this driver.
>
> ah yes, now I remember this.
next prev parent reply other threads:[~2021-02-02 10:20 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-29 17:32 [PATCH 0/6] soundwire: qcom: various improvements Srinivas Kandagatla
2021-01-29 17:32 ` [PATCH 1/6] soundwire: qcom: add support to missing transport params Srinivas Kandagatla
2021-01-29 19:20 ` Pierre-Louis Bossart
2021-02-01 15:50 ` Srinivas Kandagatla
2021-02-01 16:33 ` Pierre-Louis Bossart
2021-02-01 14:13 ` Vinod Koul
2021-02-01 15:50 ` Srinivas Kandagatla
2021-01-29 17:32 ` [PATCH 2/6] soundwire: qcom: extract version field Srinivas Kandagatla
2021-01-29 17:32 ` [PATCH 3/6] soundwire: qcom: set continue execution flag for ignored commands Srinivas Kandagatla
2021-01-29 19:21 ` Pierre-Louis Bossart
2021-02-01 14:16 ` Vinod Koul
2021-02-01 15:50 ` Srinivas Kandagatla
2021-02-02 4:46 ` Vinod Koul
2021-01-29 17:32 ` [PATCH 4/6] soundwire: qcom: start the clock during initialization Srinivas Kandagatla
2021-02-01 14:21 ` Vinod Koul
2021-02-01 15:50 ` Srinivas Kandagatla
2021-02-02 4:46 ` Vinod Koul
2021-01-29 17:32 ` [PATCH 5/6] soundwire: qcom: update register read/write routine Srinivas Kandagatla
2021-01-29 19:33 ` Pierre-Louis Bossart
2021-02-01 15:50 ` Srinivas Kandagatla
2021-02-01 16:42 ` Pierre-Louis Bossart
2021-02-02 10:19 ` Srinivas Kandagatla [this message]
2021-02-02 16:58 ` Pierre-Louis Bossart
2021-02-01 14:26 ` Vinod Koul
2021-02-01 15:50 ` Srinivas Kandagatla
2021-01-29 17:32 ` [PATCH 6/6] soundwire: qcom: add support to new interrupts Srinivas Kandagatla
2021-01-29 19:38 ` Pierre-Louis Bossart
2021-02-01 15:51 ` Srinivas Kandagatla
2021-02-01 14:31 ` Vinod Koul
2021-02-01 15:51 ` Srinivas Kandagatla
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