linux-kernel - Re: [PATCHv4 2/3] tty/serial: at91: fix hardware handshake with GPIOs

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Date:   Fri, 30 Sep 2016 13:16:06 +0200
From:   Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:     Richard Genoud <richard.genoud@...il.com>
Cc:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Nicolas Ferre <nicolas.ferre@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Cyrille Pitchen <cyrille.pitchen@...el.com>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCHv4 2/3] tty/serial: at91: fix hardware handshake with GPIOs

On 30/09/2016 at 13:04:28 +0200, Richard Genoud wrote :
> Anyway, the problematics setups are all the setups with USMODE_HWHS
> enabled on platform without Fifos or PDC,
> i.e. all platforms but sama5d2 (Cyrille, correct me if I'm wrong).
> 

This is a wrong assumption, at91rm9200 to at91sam9g45 all have a pdc.
Please, don't break those platforms.

The only affected platforms are sam9x5, sama5d3 and sama5d4.

> For instance, on sam9x5, if DMA is used, USMODE_HWHS enabled and
> RTS/CTS NOT muxed as GPIOS,
> it's like there was no flow control at all (the CTS pin doesn't
> disable the transmitter).
> 
> Since atmel HW guys said that USMODE_HWHS is broken for platforms !sama5d2,
> (cfhttps://lkml.org/lkml/2016/9/7/598 ),  I honestly didn't dig any
> further into that flag.
> 
> 
> Regards,
> Richard

-- 
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com