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Re: [PATCH v6 09/10] drivers/char: fix handling cable re-plug in XHCI console driver
- To: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 6 Sep 2022 11:21:26 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Tue, 06 Sep 2022 09:21:34 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 02.09.2022 15:17, Marek Marczykowski-Górecki wrote:
> When cable is unplugged, dbc_ensure_running() correctly detects this
> situation (DBC_CTRL_DCR flag is clear), and prevent sending data
> immediately to the device. It gets only queued in work ring buffers.
> When cable is plugged in again, subsequent dbc_flush() will send the
> buffered data.
> But there is a corner case, where no subsequent data was buffered in the
> work buffer, but a TRB was still pending. Ring the doorbell to let the
> controller re-send them. For console output it is rare corner case (TRB
> is pending for a very short time), but for console input it is very
> normal case (there is always one pending TRB for input).
>
> Extract doorbell ringing into separate function to avoid duplication.
>
> Signed-off-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
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