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

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Date:   Fri, 30 Sep 2016 14:26:57 +0200
From:   Richard Genoud <richard.genoud@...il.com>
To:     Alexandre Belloni <alexandre.belloni@...e-electrons.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

2016-09-30 13:54 GMT+02:00 Alexandre Belloni
<alexandre.belloni@...e-electrons.com>:
> On 30/09/2016 at 13:45:47 +0200, Richard Genoud wrote :
>> 2016-09-30 13:16 GMT+02:00 Alexandre Belloni
>> <alexandre.belloni@...e-electrons.com>:
>> > 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.
>> Have you tested them ?
>>
>> And why are you saying that rm9200 and g45 will be broken with this patch ?
>> If they have a pdc, they will fall in the case:
>> (atmel_use_pdc_rx(port) || atmel_use_fifo(port))
>> and thus use:
>> mode |= ATMEL_US_USMODE_HWHS;
>>
>> won't they ?
>
> Well, this patch wouldn't have my ack if it was breaking them.
It's not.
Read the code.

>However, I'm still not sure about 3/3.
As I said 2 weeks from now ( https://lkml.org/lkml/2016/9/14/263 ) the
only case where
we would want to drop the CRTSCTS flag is when there's no pin muxed
for CTS/RTS nor GPIOs.
Fell free to give a patch for that.

To be clear : this patch (2/3) unbreaks ALL platforms with GPIOs as CTS/RTS
and 3/3 unbreaks sam9x5 / sama5d3 / sama5d4 platform with CTS/RTS as !GPIOs.