From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
To: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>, 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: Mon, 1 Feb 2021 10:42:49 -0600 [thread overview]
Message-ID: <b87758d0-5862-3b4e-5a90-7b27d0c78d0d@linux.intel.com> (raw)
In-Reply-To: <3a2b5c2d-21aa-2bf5-62df-ef85c7c9293c@linaro.org>
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.
>
>
>>
>>> + 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.
>
>>
>>> + 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?
>>
>>> + 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:[~2021-02-01 18:16 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 [this message]
2021-02-02 10:19 ` Srinivas Kandagatla
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=b87758d0-5862-3b4e-5a90-7b27d0c78d0d@linux.intel.com \
--to=pierre-louis.bossart@linux.intel.com \
--cc=alsa-devel@alsa-project.org \
--cc=linux-kernel@vger.kernel.org \
--cc=sanyog.r.kale@intel.com \
--cc=srinivas.kandagatla@linaro.org \
--cc=vkoul@kernel.org \
--cc=yung-chuan.liao@linux.intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).