From: "Jan Beulich" <JBeulich@suse.com>
To: Awais Masood <awais.masood@vadion.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>,
Wei Liu <wei.liu2@citrix.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
George Dunlap <George.Dunlap@eu.citrix.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Ian Jackson <ian.jackson@eu.citrix.com>, Tim Deegan <tim@xen.org>,
xen-devel@lists.xenproject.org
Subject: Re: [PATCH v3] xen/ns16550: Fix ISR lockup on Allwinner uart
Date: Fri, 06 Oct 2017 08:50:54 -0600 [thread overview]
Message-ID: <59D7B46E020000780018330B@prv-mh.provo.novell.com> (raw)
In-Reply-To: <1507117471-12389-1-git-send-email-awais.masood@vadion.com>
>>> On 04.10.17 at 13:44, <awais.masood@vadion.com> wrote:
> This patch fixes an ISR lockup seen on Allwinner uart
>
> On Allwinner H5, serial driver goes into an infinite loop
> when interrupts are enabled. The reason is a residual
> "busy detect" interrupt. Since the condition UART_IIR_NOINT
> will not be true unless this interrupt is cleared, the
> interrupt handler will remain locked up in this while loop.
>
> A HW quirk fix was previously added for designware uart under
> commit:
> 50417cd978aa54930d065ac1f139f935d14af76d
>
> It checks for a busy condition during setup and clears the
> condition by reading UART_USR register.
>
> On Allwinner hardware, the "busy detect" condition occurs
> later because an LCR write is performed during setup 'after'
> this clear and if uart is busy, the "busy detect" condition
> will trigger again and cause the ISR lockup.
>
> To solve this problem, the same UART_USR read operation needs
> to be performed within the interrupt handler to clear this
> condition.
>
> Linux dw 8250 driver also handles this condition within
> interrupt handler
> http://elixir.free-electrons.com/linux/latest/source/drivers/tty/serial/8250/
> 8250_dw.c#L233
>
> Tested on Orange Pi PC2 (H5). This issue is seen on H3
> as well and the same fix works.
>
> Signed-off-by: Awais Masood <awais.masood@vadion.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel
next prev parent reply other threads:[~2017-10-06 14:51 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-19 13:38 [PATCH 0/2] xen/arm64/ns16550: Support for Allwinner H5 SoC Awais Masood
2017-09-19 13:38 ` [PATCH 1/2] xen/arm64: Add Support for Allwinner H5 (sun50i) Awais Masood
2017-09-19 13:50 ` Jan Beulich
2017-09-19 13:38 ` [PATCH 2/2] xen/ns16550: Fix ISR lockup on Designware 8250 (H5) Awais Masood
2017-09-19 13:49 ` Jan Beulich
2017-09-26 9:37 ` [PATCH v2 0/2] xen/arm64/ns16550: Support for Allwinner H5 SoC Awais Masood
2017-09-26 9:37 ` [PATCH v2 1/2] xen/arm64: Add Support for Allwinner H5 (sun50i) Awais Masood
2017-09-28 20:03 ` Julien Grall
2017-09-28 22:49 ` Andre Przywara
2017-09-29 16:35 ` Andre Przywara
2017-10-04 9:16 ` Awais Masood
2017-10-04 9:26 ` Andre Przywara
2017-10-04 9:39 ` Awais Masood
2017-10-04 10:03 ` Andre Przywara
2017-10-03 11:32 ` Julien Grall
2017-09-26 9:37 ` [PATCH v2 2/2] xen/ns16550: Fix ISR lockup on Designware 8250 (H5) Awais Masood
2017-09-26 11:58 ` Jan Beulich
2017-10-04 11:44 ` [PATCH v3] xen/ns16550: Fix ISR lockup on Allwinner uart Awais Masood
2017-10-06 14:50 ` Jan Beulich [this message]
2017-10-10 23:59 ` Stefano Stabellini
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=59D7B46E020000780018330B@prv-mh.provo.novell.com \
--to=jbeulich@suse.com \
--cc=George.Dunlap@eu.citrix.com \
--cc=andrew.cooper3@citrix.com \
--cc=awais.masood@vadion.com \
--cc=ian.jackson@eu.citrix.com \
--cc=konrad.wilk@oracle.com \
--cc=sstabellini@kernel.org \
--cc=tim@xen.org \
--cc=wei.liu2@citrix.com \
--cc=xen-devel@lists.xenproject.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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.