From: Lina Iyer <ilina@codeaurora.org>
To: Stephen Boyd <swboyd@chromium.org>
Cc: andy.gross@linaro.org, bjorn.andersson@linaro.org,
linux-arm-msm@vger.kernel.org, linux-soc@vger.kernel.org,
rnayak@codeaurora.org, linux-kernel@vger.kernel.org,
linux-pm@vger.kernel.org, dianders@chromium.org,
mkshah@codeaurora.org,
"Raju P.L.S.S.S.N" <rplsssn@codeaurora.org>
Subject: Re: [PATCH 1/2] drivers: qcom: rpmh-rsc: simplify TCS locking
Date: Mon, 22 Jul 2019 10:20:03 -0600 [thread overview]
Message-ID: <20190722162003.GG25567@codeaurora.org> (raw)
In-Reply-To: <5d3209e7.1c69fb81.5ef1.5195@mx.google.com>
On Fri, Jul 19 2019 at 12:20 -0600, Stephen Boyd wrote:
>Quoting Lina Iyer (2019-07-01 08:29:06)
>> From: "Raju P.L.S.S.S.N" <rplsssn@codeaurora.org>
>>
>> tcs->lock was introduced to serialize access with in TCS group. But
>> even without tcs->lock, drv->lock is serving the same purpose. So
>> use a single drv->lock.
>
>Isn't the downside now that we're going to be serializing access to the
>different TCSes when two are being written in parallel or waited on? I
>thought that was the whole point of splitting the lock into a TCS lock
>and a general "driver" lock that protects the global driver state vs.
>the specific TCS state.
>
Yes but we were holding the drv->lock as well as tcs->lock for the most
critical of the path anyways (writing to TCS). The added complexity
doesn't seem to help reduce the latency that it expected to reduce.
>>
>> Other optimizations include -
>> - Remove locking around clear_bit() in IRQ handler. clear_bit() is
>> atomic.
>> - Remove redundant read of TCS registers.
>> - Use spin_lock instead of _irq variants as the locks are not held
>> in interrupt context.
>
>Can you please split this patch up into 3 or 4 different patches? I'm
>not sure why any of these patches are marked with Fixes either. It's an
>optimization patch, not a fix patch, unless the optimization is really
>large somehow?
>
Okay. I will try that.
>>
>> Fixes: 658628 ("drivers: qcom: rpmh-rsc: add RPMH controller for QCOM
>> SoCs")
>> Signed-off-by: Raju P.L.S.S.S.N <rplsssn@codeaurora.org>
>> Signed-off-by: Lina Iyer <ilina@codeaurora.org>
>> ---
>> drivers/soc/qcom/rpmh-internal.h | 2 --
>> drivers/soc/qcom/rpmh-rsc.c | 37 +++++++++++---------------------
>> drivers/soc/qcom/rpmh.c | 20 +++++++----------
>> 3 files changed, 21 insertions(+), 38 deletions(-)
>>
>> diff --git a/drivers/soc/qcom/rpmh-internal.h b/drivers/soc/qcom/rpmh-internal.h
>> index a7bbbb67991c..969d5030860e 100644
>> --- a/drivers/soc/qcom/rpmh-internal.h
>> +++ b/drivers/soc/qcom/rpmh-internal.h
>> diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c
>> index e278fc11fe5c..92461311aef3 100644
>> --- a/drivers/soc/qcom/rpmh-rsc.c
>> +++ b/drivers/soc/qcom/rpmh-rsc.c
>> @@ -93,8 +93,7 @@ static void write_tcs_reg_sync(struct rsc_drv *drv, int reg, int tcs_id,
>>
>> static bool tcs_is_free(struct rsc_drv *drv, int tcs_id)
>> {
>> - return !test_bit(tcs_id, drv->tcs_in_use) &&
>> - read_tcs_reg(drv, RSC_DRV_STATUS, tcs_id, 0);
>> + return !test_bit(tcs_id, drv->tcs_in_use);
>
>This can be a diffedjusted rent patch. Why is reading the tcs register
>redundant? Please put that information in the commit text.
>
The tcs_in_use, is adjusted along with the DRV_STS and reading the
tcs_in_use should be enough.
Thanks for your review Stephen.
--Lina
next prev parent reply other threads:[~2019-07-22 16:20 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-01 15:29 [PATCH 1/2] drivers: qcom: rpmh-rsc: simplify TCS locking Lina Iyer
2019-07-01 15:29 ` [PATCH 2/2] drivers: qcom: rpmh-rsc: fix read back of trigger register Lina Iyer
2019-07-01 15:53 ` Lina Iyer
2019-07-19 18:22 ` Stephen Boyd
2019-07-22 15:51 ` Lina Iyer
2019-07-01 15:52 ` [PATCH 1/2] drivers: qcom: rpmh-rsc: simplify TCS locking Lina Iyer
2019-07-19 18:20 ` Stephen Boyd
2019-07-22 16:20 ` Lina Iyer [this message]
2019-07-22 18:18 ` Stephen Boyd
2019-07-22 19:46 ` Lina Iyer
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=20190722162003.GG25567@codeaurora.org \
--to=ilina@codeaurora.org \
--cc=andy.gross@linaro.org \
--cc=bjorn.andersson@linaro.org \
--cc=dianders@chromium.org \
--cc=linux-arm-msm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pm@vger.kernel.org \
--cc=linux-soc@vger.kernel.org \
--cc=mkshah@codeaurora.org \
--cc=rnayak@codeaurora.org \
--cc=rplsssn@codeaurora.org \
--cc=swboyd@chromium.org \
/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).