linux-kernel - Re: [PATCH] serial: 8250_dw: Improve unwritable LCR workaround

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Message-ID: <CAAYSxhqMGOspc7Y1QEa68W2ADpf-k33SOH4nHWhnis_71cyKsQ@mail.gmail.com>
Date:	Tue, 1 Oct 2013 10:13:11 -0700
From:	Tim Kryger <tim.kryger@...aro.org>
To:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
	Patch Tracking <patches@...aro.org>
Subject: Re: [PATCH] serial: 8250_dw: Improve unwritable LCR workaround

On Fri, Sep 27, 2013 at 12:49 AM, Heikki Krogerus
<heikki.krogerus@...ux.intel.com> wrote:

> OK. The LCR issue is only a problem when the UART is configured with
> the busy functionality (UART_16550_COMPATIBLE == NO). Otherwise LRC is
> always accessible and this is not necessary.

Reading through the latest DW databook, I believe you are correct.

> We need a flag for the UART_16550_COMPATIBLE configuration, and
> use this WA based on that.

If I adjust the workaround to force the UART idle only when an LCR
write was ignored rather than doing it prior to any LCR write, would
that address your concerns?
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