linux-kernel - Re: [PATCH v1 3/4] max3100: adds console support for MAX3100

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Message-ID: <v2ocabda6421004080231r7b7a734ao9fce206a82bf944b@mail.gmail.com>
Date:	Thu, 8 Apr 2010 11:31:09 +0200
From:	christian pellegrin <chripell@...e.org>
To:	Feng Tang <feng.tang@...el.com>
Cc:	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"greg@...ah.com" <greg@...ah.com>,
	"david-b@...bell.net" <david-b@...bell.net>,
	"grant.likely@...retlab.ca" <grant.likely@...retlab.ca>,
	"alan@...rguk.ukuu.org.uk" <alan@...rguk.ukuu.org.uk>,
	"spi-devel-general@...ts.sourceforge.net" 
	<spi-devel-general@...ts.sourceforge.net>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 3/4] max3100: adds console support for MAX3100

On Mon, Mar 29, 2010 at 4:48 AM, Feng Tang <feng.tang@...el.com> wrote:

>> +             tx |= MAX3100_WD | MAX3100_RTS;
>
> Does this imply to have to work with HW flow control? on my platform
> I have to remove the RTS bit to make it work.
>

Finally I had time to check this. If you compare the 8250 (or similar)
data-sheet with the MAX31x0 one you see that the handling of the
RTX/CTS bits is exactly the same (8250 about RTS bit for example:
"When any of these bits are cleared, the associated output is forced
high." and MAX3110: "Request-to-Send Bit. Controls the state of the
RTS output. This bit is reset on power-up (RTS
bit = 0 sets the RTS pin = logic high)."). If you look at the 8250.c
driver (grep for UART_MCR_RTS) you notice that the bit is set on
device open (together with DTR of course). So I think the driver is
doing the right thing here.

-- 
Christian Pellegrin, see http://www.evolware.org/chri/
"Real Programmers don't play tennis, or any other sport which requires
you to change clothes. Mountain climbing is OK, and Real Programmers
wear their climbing boots to work in case a mountain should suddenly
spring up in the middle of the computer room."
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