From: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
To: Yong Wu <yong.wu@mediatek.com>,
Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Cc: Krzysztof Kozlowski <krzk@kernel.org>,
Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
Robin Murphy <robin.murphy@arm.com>,
Tomasz Figa <tfiga@chromium.org>,
linux-mediatek@lists.infradead.org, srv_heupstream@mediatek.com,
linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
iommu@lists.linux-foundation.org, youlin.pei@mediatek.com,
anan.sun@mediatek.com, lc.kan@mediatek.com, yi.kuo@mediatek.com,
anthony.huang@mediatek.com, Rob Herring <robh+dt@kernel.org>,
Matthias Brugger <matthias.bgg@gmail.com>
Subject: Re: [PATCH 3/4] memory: mtk-smi: Add sleep ctrl function
Date: Tue, 7 Dec 2021 13:16:52 +0100 [thread overview]
Message-ID: <85ef182a-8ebe-7dbb-aa95-35e77cbb072c@collabora.com> (raw)
In-Reply-To: <e1d72db69f424b9ee8987b7bafa7423c672ceef1.camel@mediatek.com>
Il 07/12/21 13:10, Yong Wu ha scritto:
> On Tue, 2021-12-07 at 09:56 +0100, AngeloGioacchino Del Regno wrote:
>> Il 07/12/21 07:24, Yong Wu ha scritto:
>>> Hi AngeloGioacchino,
>>>
>>> Thanks for your review.
>>>
>>> On Mon, 2021-12-06 at 16:08 +0100, AngeloGioacchino Del Regno
>>> wrote:
>>>> Il 03/12/21 07:40, Yong Wu ha scritto:
>>>>> sleep control means that when the larb go to sleep, we should
>>>>> wait
>>>>> a bit
>>>>> until all the current commands are finished. thus, when the
>>>>> larb
>>>>> runtime
>>>>> suspend, we need enable this function to wait until all the
>>>>> existed
>>>>> command are finished. when the larb resume, just disable this
>>>>> function.
>>>>> This function only improve the safe of bus. Add a new flag for
>>>>> this
>>>>> function. Prepare for mt8186.
>>>>>
>>>>> Signed-off-by: Anan Sun <anan.sun@mediatek.com>
>>>>> Signed-off-by: Yong Wu <yong.wu@mediatek.com>
>>>>> ---
>>>>> drivers/memory/mtk-smi.c | 39
>>>>> +++++++++++++++++++++++++++++++++++----
>>>>> 1 file changed, 35 insertions(+), 4 deletions(-)
>>>
>>> [snip]
>>>
>>>>> static int __maybe_unused mtk_smi_larb_suspend(struct device
>>>>> *dev)
>>>>> {
>>>>> struct mtk_smi_larb *larb = dev_get_drvdata(dev);
>>>>> + int ret = 0;
>>>>> +
>>>>> + if (MTK_SMI_CAPS(larb->larb_gen->flags_general,
>>>>> MTK_SMI_FLAG_SLEEP_CTL))
>>>>> + ret = mtk_smi_larb_sleep_ctrl(dev, true);
>>>>
>>>> Sorry but what happens if SLP_PROT_RDY is not getting set
>>>> properly?
>>>> From what I can understand in the commit description that you
>>>> wrote,
>>>> if we reach
>>>> the timeout, then the LARB transactions are not over....
>>>>
>>>> I see that you are indeed returning a failure here, but you are
>>>> also
>>>> turning off
>>>> the clocks regardless of whether we get a failure or a success;
>>>> I'm
>>>> not sure that
>>>> this is right, as this may leave the hardware in an unpredictable
>>>> state (since
>>>> there were some more LARB transactions that didn't go through),
>>>> leading to crashes
>>>> at system resume (or when retyring to suspend).
>>>
>>> Thanks for this question. In theory you are right. In this case,
>>> the
>>> bus already hang.
>>>
>>> We only printed a fail log in this patch. If this fail happens, we
>>> should request the master to check which case cause the larb hang.
>>>
>>> If the master has a good reason or limitation, the hang is
>>> expected, I
>>> think we have to add larb reset in this fail case: Reset the larb
>>> when
>>> the larb runtime resume.
>>>
>>
>> Think about the case in which the system gets resumed only partially
>> due to a
>>
>> failure during resume of some driver, or due to a RTC or arch timer
>> resume and
>> suspend right after... or perhaps during runtime suspend/resume of
>> some devices.
>> In that case, we definitely want to avoid any kind of failure point
>> that would
>> lead to a system crash, or any kind of user noticeable (or UX
>> disrupting) "strange
>> behavior".
>>
>> I think that we should make sure that the system suspends cleanly,
>> instead of
>> patching up any possible leftover issue at resume time: if this is
>> doable with
>> a LARB reset in suspend error case, that looks like being a good
>> option indeed.
>>
>> As a side note, thinking about UX, losing a little more time during
>> suspend is
>> nothing really noticeable for the user... on the other hand, spending
>> more time
>> during resume may be something noticeable to the user.
>> For this reason, I think that guaranteeing that the system resumes as
>> fast as
>> possible is very important, which adds up to the need of suspending
>> cleanly.
>
> Thanks for this comment. I will put it in the suspend when adding the
> reset. But I have no plan to add it in this version since I don't see
> the need for this right now. Maybe I should add a comment in the code
> for this.
>
What I understand from your reply is that the reset is not trivial work
and needs quite some time to be done properly; in that case: yes, please
add a TODO comment that explains the situation and the discussed solution.
Also, since this SLP_PROT_RDY flag seems to be very nice, just a simple
question: is this a new feature in the SMI IP of MT8186, or is there anything
similar that we may use on other SoCs, like 8183, 8192, 8195, as a follow-up
of this series?
>>
>>> Fortunately, we have never got this issue. We could add this reset
>>> when
>>> necessary. Is this OK for you?
>>>
>>> Thanks.
>>>
>>>>
>>>>>
>>>>> clk_bulk_disable_unprepare(larb->smi.clk_num, larb-
>>>>>> smi.clks);
>>>>> - return 0;
>>>>> + return ret;
>>>>> }
>>>>>
>>>>> static const struct dev_pm_ops smi_larb_pm_ops = {
>>>>>
>>>>
>>>>
>>
>>
_______________________________________________
Linux-mediatek mailing list
Linux-mediatek@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-mediatek
next prev parent reply other threads:[~2021-12-07 12:18 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-03 6:40 [PATCH 0/4] MT8186 SMI SUPPORT Yong Wu
2021-12-03 6:40 ` [PATCH 1/4] dt-bindings: memory: mediatek: Correct the minItems of clk for larbs Yong Wu
2021-12-03 23:34 ` Rob Herring
2021-12-13 6:48 ` Yong Wu
2021-12-13 20:30 ` Rob Herring
2021-12-03 6:40 ` [PATCH 2/4] dt-bindings: memory: mediatek: Add mt8186 support Yong Wu
2021-12-13 20:31 ` Rob Herring
2021-12-03 6:40 ` [PATCH 3/4] memory: mtk-smi: Add sleep ctrl function Yong Wu
2021-12-04 11:48 ` Krzysztof Kozlowski
2021-12-06 8:15 ` Yong Wu
2021-12-06 15:08 ` AngeloGioacchino Del Regno
2021-12-07 6:24 ` Yong Wu
2021-12-07 8:56 ` AngeloGioacchino Del Regno
2021-12-07 12:10 ` Yong Wu
2021-12-07 12:16 ` AngeloGioacchino Del Regno [this message]
2021-12-08 2:42 ` Yong Wu
2021-12-09 9:12 ` AngeloGioacchino Del Regno
2021-12-03 6:40 ` [PATCH 4/4] memory: mtk-smi: mt8186: Add smi support Yong Wu
2021-12-06 15:00 ` AngeloGioacchino Del Regno
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=85ef182a-8ebe-7dbb-aa95-35e77cbb072c@collabora.com \
--to=angelogioacchino.delregno@collabora.com \
--cc=anan.sun@mediatek.com \
--cc=anthony.huang@mediatek.com \
--cc=devicetree@vger.kernel.org \
--cc=iommu@lists.linux-foundation.org \
--cc=joro@8bytes.org \
--cc=krzk@kernel.org \
--cc=krzysztof.kozlowski@canonical.com \
--cc=lc.kan@mediatek.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mediatek@lists.infradead.org \
--cc=matthias.bgg@gmail.com \
--cc=robh+dt@kernel.org \
--cc=robin.murphy@arm.com \
--cc=srv_heupstream@mediatek.com \
--cc=tfiga@chromium.org \
--cc=will@kernel.org \
--cc=yi.kuo@mediatek.com \
--cc=yong.wu@mediatek.com \
--cc=youlin.pei@mediatek.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).