linux-kernel - Re: [PATCH RESEND 2/2] serial: 8250: omap: Move pm_runtime_get

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Message-ID: <20241014172237.63e9625f@akair>
Date: Mon, 14 Oct 2024 17:22:37 +0200
From: Andreas Kemnade <andreas@...nade.info>
To: Bin Liu <binmlist@...il.com>
Cc: Judith Mendez <jm@...com>, Santosh Shilimkar <ssantosh@...nel.org>,
 Kevin Hilman <khilman@...nel.org>, Linus Walleij
 <linus.walleij@...aro.org>, Bartosz Golaszewski <brgl@...ev.pl>,
 linux-omap@...r.kernel.org, linux-gpio@...r.kernel.org,
 linux-kernel@...r.kernel.org, Bin Liu <b-liu@...com>,
 linux-serial@...r.kernel.org
Subject: Re: [PATCH RESEND 2/2] serial: 8250: omap: Move pm_runtime_get_sync

Am Sun, 13 Oct 2024 21:52:05 -0500
schrieb Bin Liu <binmlist@...il.com>:

> Hi,
> 
> Somehow this email wasn’t cc’d to my company email account
> b-liu@...com, so I am replying from my personal email which
> subscribed to the mailing list, and sorry if the formatting is wrong
> since I am writing this response on my phone. 
> 
> On Oct 12, 2024, at 7:27 AM, Andreas Kemnade <andreas@...nade.info>
> wrote:
> > 
> > Am Fri, 11 Oct 2024 12:33:56 -0500
> > schrieb Judith Mendez <jm@...com>:
> > 
> > Currently in omap_8250_shutdown, the dma->rx_running
> >> flag is set to zero in omap_8250_rx_dma_flush. Next
> >> pm_runtime_get_sync is called, which is a runtime
> >> resume call stack which can re-set the flag. When the
> >> call omap_8250_shutdown returns, the flag is expected
> >> to be UN-SET, but this is not the case. This is causing
> >> issues the next time UART is re-opened and omap_8250_rx_dma
> >> is called. Fix by moving pm_runtime_get_sync before the
> >> omap_8250_rx_dma_flush.
> >> 
> >> Signed-off-by: Bin Liu <b-liu@...com>
> >> Signed-off-by: Judith Mendez <jm@...com>
> >> 
> > Is this a theorectical problem or some real practical problem?
> > So you are running a system with runtime pm enabled on serial
> > console.
> > How did you come across this issue?
> > I could run the serial console/getty with runtime pm autosuspend
> > enabled without issues all the years.
> > 
> Yes this is a real issue reported on AM335x. Please see the report
> linked below.
> 
> PROCESSOR-SDK-AM335X: Possible bug in 8250_omap UART driver -
> Processors forum - Processors - TI E2E support forums e2e.ti.com
> 
> 
Thanks for information, so it looks like material for backporting.
Maybe add the link in the description and add the cc stable and 
add back the fixes tag.

Regards,
Andreas