linux-kernel - [PATCH v2 0/2] serial: 8250: Mitigate Tx stall risk for Aspeed VUARTs

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Date:   Wed, 19 May 2021 09:37:02 +0930
From:   Andrew Jeffery <andrew@...id.au>
To:     linux-serial@...r.kernel.org
Cc:     gregkh@...uxfoundation.org, jirislaby@...nel.org, joel@....id.au,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-aspeed@...ts.ozlabs.org, openbmc@...ts.ozlabs.org,
        jenmin_yuan@...eedtech.com, ryan_chen@...eedtech.com,
        miltonm@...ibm.com
Subject: [PATCH v2 0/2] serial: 8250: Mitigate Tx stall risk for Aspeed VUARTs

Hello,

Briefly, the series works around a hardware race condition in the Tx path for
Aspeed virtual UARTs. A write burst to THR on the APB interface may provoke a
transfer stall where LSR[DR] on the LPC interface remains clear despite the
presence of data in the Rx FIFO.

For the work-around patch, v2 addresses the request for a comment about the use
of serial_in():

https://lore.kernel.org/lkml/d7918dcf-b938-498c-a012-3d93a748431b@www.fastmail.com/T/#md75702fbc3704bd4b375f1251a1415bcddea26a3

The second patch addresses the request for use of BIT() instead of an explicit
shift by converting all of the UART_{CAP,BUG}_* macros.

Please review!

Andrew

Andrew Jeffery (2):
  serial: 8250: Add UART_BUG_TXRACE workaround for Aspeed VUART
  serial: 8250: Use BIT(x) for UART_{CAP,BUG}_*

 drivers/tty/serial/8250/8250.h              | 32 +++++++++++----------
 drivers/tty/serial/8250/8250_aspeed_vuart.c |  1 +
 drivers/tty/serial/8250/8250_port.c         | 10 +++++++
 3 files changed, 28 insertions(+), 15 deletions(-)

-- 
2.30.2