linux-kernel - Re: [PATCH v3 2/2] tty/serial: atmel: add ISO7816 support

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Message-ID: <20180905141454.xh2ovvpoth6s76ne@M43218.corp.atmel.com>
Date:   Wed, 5 Sep 2018 16:14:54 +0200
From:   Ludovic Desroches <ludovic.desroches@...rochip.com>
To:     Richard Genoud <richard.genoud@...il.com>
CC:     <linux-serial@...r.kernel.org>, <linux-arch@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <alexandre.belloni@...tlin.com>, <arnd@...db.de>,
        <gregkh@...uxfoundation.org>, <linux-kernel@...r.kernel.org>,
        <jslaby@...e.com>, Nicolas Ferre <nicolas.ferre@...rochip.com>
Subject: Re: [PATCH v3 2/2] tty/serial: atmel: add ISO7816 support

On Wed, Sep 05, 2018 at 03:53:02PM +0200, Richard Genoud wrote:
> [added Nicolas back in the thread, he was removed somehow]
> 
> Hi Ludovic !
> 
> On 05/09/2018 14:43, Ludovic Desroches wrote:
> > Hi Richard,
> > 
> > On Thu, Aug 09, 2018 at 01:30:35PM +0200, Ludovic Desroches wrote:
> >> Hi Richard,
> >>
> >> On Thu, Aug 09, 2018 at 10:47:17AM +0200, Richard Genoud wrote:
> >>> Hi !
> >>>
> >>> On 07/08/2018 15:00, Ludovic Desroches wrote:
> >>>> From: Nicolas Ferre <nicolas.ferre@...rochip.com>
> >>>>
> >>>> When mode is set in atmel_config_iso7816() we backup last RS232 mode
> >>>> for coming back to this mode if requested.
> >>>> Also allow setup of T=0 and T=1 parameter and basic support in set_termios
> >>>> function as well.
> >>>>
> >>>> Signed-off-by: Nicolas Ferre <nicolas.ferre@...rochip.com>
> >>>> [ludovic.desroches@...rochip.com: rebase, add check on fidi ratio, checkpatch fixes]
> >>>> Signed-off-by: Ludovic Desroches <ludovic.desroches@...rochip.com>
> >>>> ---
> >>>>  drivers/tty/serial/atmel_serial.c | 211 +++++++++++++++++++++++++++++++++++---
> >>>>  drivers/tty/serial/atmel_serial.h |   6 +-
> >>>>  2 files changed, 201 insertions(+), 16 deletions(-)
> >>>>
> >>>> diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
> >>>> index 8e4428725848..4a7ec44b0ace 100644
> >>>> --- a/drivers/tty/serial/atmel_serial.c
> >>>> +++ b/drivers/tty/serial/atmel_serial.c
> >>
> >> [...]
> >>
> >>>>  #if defined(CONFIG_OF)
> >>>> +static struct atmel_uart_pdata at91rm9200_pdata = {
> >>>> +	.fidi_min = 1,
> >>>> +	.fidi_max = 2047,
> >>>> +};
> >>>> +
> >>>> +static struct atmel_uart_pdata at91sam9260_pdata = {
> >>>> +	.fidi_min = 1,
> >>>> +	.fidi_max = 2047,
> >>>> +};
> >>>> +
> >>>> +static struct atmel_uart_pdata sama5d3_pdata = {
> >>>> +	.fidi_min = 3,
> >>>> +	.fidi_max = 65535,
> >>> Are you sure this is for sama5d3 ?
> >>> From the datasheets I have, 65535 is for sama5d4/sama5d2
> >>
> >> I checked it and I missed it. What a pity... In fact, it's a bit more
> >> tricky since the min value for d3 is 3 and no longer 1.
> >>
> >>> And also, you'll have to s/atmel,at91sam9260-usart/atmel,sama5d2-usart/g
> >>> in sama5d{2,4}.dtsi
> >>>
> >>
> >> Yes, I planed to send it later but I can add those patches within this
> >> set of patches. 
> >>
> >>> But I wonder if it could be detected via ATMEL_US_VERSION instead ?
> >>>
> >>
> >> I have not checked, I tend to prefer the compatible string for this kind
> >> of thing. But as we already use the version number, I can investigate
> >> this solution if it's the one you prefer.
> >>
> > 
> > ping about this question still in suspend in order to prepare a new version.
> Well, if we use the compatible string for this, we will have to add :
> - atmel,sama5d2-usart
> - atmel,sama5d3-usart
> - (maybe others ?)
> to the already existing :
> - atmel,at91sam9260-usart
> - atmel,at91rm9200-usart
> just for setting different limits on the fidi register.
> IMHO, it seems a bit overkill. Moreover, the ATMEL_US_VERSION has
> already been read, so...
> But if you think adding compatible strings is a better/cleaner solution, just convince me ! :)

I won't try to convince you since we already use the ATMEL_US_VERSION.
IMHO we should use the compatible string from the beginning but we
didn't have the necessary DT experience at this time to figure out it
was probably better than relying on the version number which can be not
incrimented by error.

I'll check the values of the ATMEL_US_VERSION and use it if everything
is okay.

Regards

Ludovic