From: Vijaya Krishna Nivarthi <quic_vnivarth@quicinc.com>
To: Marek Szyprowski <m.szyprowski@samsung.com>,
<gregkh@linuxfoundation.org>, <jirislaby@kernel.org>,
<linux-serial@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Cc: <quic_msavaliy@quicinc.com>, <dianders@chromium.org>,
<mka@chromium.org>, <swboyd@chromium.org>
Subject: Re: [V4] serial: core: Do stop_rx in suspend path for console if console_suspend is disabled
Date: Sat, 4 Jun 2022 00:24:23 +0530 [thread overview]
Message-ID: <f525c352-d995-0589-584f-0e9acf419f80@quicinc.com> (raw)
In-Reply-To: <cb802fb1-d0b8-68af-1c04-f73bc1beca77@quicinc.com>
Hi,
On 6/2/2022 9:12 PM, Vijaya Krishna Nivarthi wrote:
> Hi,
>
>
> On 6/2/2022 3:55 AM, Marek Szyprowski wrote:
>> Hi,
>>
>> On 01.06.2022 13:24, Vijaya Krishna Nivarthi wrote:
>>> On 5/24/2022 5:24 PM, Marek Szyprowski wrote:
>>>> On 23.05.2022 23:32, Marek Szyprowski wrote:
>>>>> Hi,
>>>>>
>>>>> On 16.05.2022 11:20, Vijaya Krishna Nivarthi wrote:
>>>>>> For the case of console_suspend disabled, if back to back
>>>>>> suspend/resume
>>>>>> test is executed, at the end of test, sometimes console would
>>>>>> appear to
>>>>>> be frozen not responding to input. This would happen because, during
>>>>>> resume, rx transactions can come in before system is ready,
>>>>>> malfunction
>>>>>> of rx happens in turn resulting in console appearing to be stuck.
>>>>>>
>>>>>> Do a stop_rx in suspend sequence to prevent this.
>>>>>>
>>>>>> Signed-off-by: Vijaya Krishna Nivarthi <quic_vnivarth@quicinc.com>
>>>>>> ---
>>>>>> v4: moved the change to serial core to apply for all drivers
>>>>>> v3: swapped the order of conditions to be more human readable
>>>>>> v2: restricted patch to contain only stop_rx in suspend sequence
>>>>>> v1: intial patch contained 2 additional unrelated changes in
>>>>>> vicinity
>>>>>> ---
>>>>> This patch landed recently in linux-next as commit c9d2325cdb92
>>>>> ("serial: core: Do stop_rx in suspend path for console if
>>>>> console_suspend is disabled").
>>>>>
>>>>> Unfortunately it breaks console operation on my test systems after
>>>>> system suspend/resume cycle if 'no_console_suspend' kernel parameter
>>>>> is present. System properly resumes from suspend, the console
>>>>> displays
>>>>> all the messages and even command line prompt, but then doesn't react
>>>>> on any input. If I remove the 'no_console_suspend' parameter, the
>>>>> console is again operational after system suspend/resume cycle.
>>>>> Before
>>>>> this patch it worked fine regardless the 'no_console_suspend'
>>>>> parameter.
>>>>>
>>>>> If this matters, the test system is ARM 32bit Samsung
>>>>> Exynos5422-based
>>>>> Odroid XU3lite board.
>>>> One more information. This issue can be easily reproduced with
>>>> QEMU. It
>>>> happens both on ARM 32bit and ARM 64bit QEMU's 'virt' machines when
>>>> 'no_console_suspend' is added to kernel's cmdline.
>>>>
>>> Ideally, as comments indicate, the set_termios should have done
>>> stop_rx at begin and start_rx at end to take care of this issue.
>>>
>>> This is probably missing in your driver. Can we check if this can be
>>> fixed?
>> Sure, just point me what need to be added in amba-pl011.c and
>> samsung_tty.c. I've briefly compared the suspend/resume paths of those
>> drivers with other drivers and I don't see anything missing there.
>>
>>> OR other option is
>>>
>>> Add a start_rx in uart_resume_port after call to set_termios to handle
>>> this scenario for other drivers.
Since start_rx is not exposed it doesn't seem like we will be able to
handle it in core.
In your drivers, Can we add a call to stop_rx at begin of set_termios
and then undo it at end?
That would ensure that set_termios functionality is unaffected while
fixing the broken cases?
If that's not an option we will have to go back to a previous version of
limiting the change to qcom driver.
Thank you.
>>>
>>> Please let me know if there are any concerns for this options.
>> IMHO this looks like an issue that affects lots of drivers and it should
>> be handled in the core.
>
> Sure, we will look into both aspects and get back as soon as possible.
>
> Thank you.
>
>>
>> > ...
>>
>> Best regards
next prev parent reply other threads:[~2022-06-03 18:54 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-16 9:20 [V4] serial: core: Do stop_rx in suspend path for console if console_suspend is disabled Vijaya Krishna Nivarthi
[not found] ` <CGME20220523213246eucas1p2d0da08d931a996cd3410eda1c2fd48c0@eucas1p2.samsung.com>
2022-05-23 21:32 ` Marek Szyprowski
[not found] ` <CGME20220524115408eucas1p1ddda7aae4db0a65a7d67d6f8c59d404b@eucas1p1.samsung.com>
2022-05-24 11:54 ` Marek Szyprowski
2022-06-01 11:24 ` Vijaya Krishna Nivarthi
2022-06-01 22:25 ` Marek Szyprowski
2022-06-02 15:42 ` Vijaya Krishna Nivarthi
2022-06-03 18:54 ` Vijaya Krishna Nivarthi [this message]
2022-06-03 19:28 ` Doug Anderson
2022-06-06 12:30 ` Vijaya Krishna Nivarthi
2022-06-07 13:22 ` Greg KH
2022-06-07 13:25 ` Vijaya Krishna Nivarthi
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