linux-kernel - Re: [PATCH 1/3] mfd: Add support for FTDI FT232H devices

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Message-ID: <20170725143441.2debeff6@crub>
Date:   Tue, 25 Jul 2017 14:34:41 +0200
From:   Anatolij Gustschin <agust@...x.de>
To:     Johan Hovold <johan@...nel.org>
Cc:     Lee Jones <lee.jones@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Alan Tull <atull@...nel.org>,
        Moritz Fischer <moritz.fischer@...us.com>,
        linux-gpio@...r.kernel.org, linux-fpga@...r.kernel.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        David Laight <David.Laight@...lab.com>
Subject: Re: [PATCH 1/3] mfd: Add support for FTDI FT232H devices

On Tue, 25 Jul 2017 13:49:08 +0200
Johan Hovold johan@...nel.org wrote:

>On Wed, Jul 19, 2017 at 01:58:30PM +0200, Anatolij Gustschin wrote:
>> On Mon, 10 Jul 2017 14:52:10 +0200
>> Johan Hovold johan@...nel.org wrote:
>>   
>> >On Thu, Jul 06, 2017 at 10:49:16PM +0200, Anatolij Gustschin wrote:  
>> >> Add USB part with common functions for USB-GPIO/I2C/SPI master
>> >> adapters. These allow communication with chip's control, transmit
>> >> and receive endpoints and will be used by various FT232H drivers.    
>> >  
>> >> +static const struct mfd_cell ftdi_cells[] = {
>> >> +	{ .name = "ftdi-cbus-gpio", },
>> >> +	{ .name = "ftdi-mpsse-i2c", },
>> >> +	{ .name = "ftdi-mpsse-spi", },
>> >> +	{ .name = "ftdi-fifo-fpp-mgr", },
>> >> +};    
>> >
>> >Correct me if I'm wrong, but aren't these modes really mutually
>> >exclusive, possibly with exception of cbus-gpio (some pins are at least
>> >available as GPIOs in MPSSE mode)? Then MFD is not is not the right fit
>> >here either.  
>> 
>> MPSSE and FIFO modes are mutually exclusive, but I'm not sure about
>> MPSSE and CBUS-GPIO. CBUS-GPIO didn't work as expected when I was
>> testing with MPSSE SPI master driver, but maybe it is a driver issue.  
>
>Yes, that wasn't clear to me either from just looking at the data
>sheets. MPSSE seems to deal with its GPIOs differently.

yes, the GPIOs are at different pins in MPSSE mode and these pins are
controlled via writes/reads to/from bulk endpoint with MPSSE commands.

>> FT245 FIFO and CBUS GPIO can be switched by a control request, when
>> FIFO mode is configured in the EEPROM.  
>
>Since the set_bitmode command is used to control the CBUS gpios, does
>that mean that they cannot be toggled independently while FIFO mode is
>in use (as the same command is used to set FIFO mode)?

yes.

Thanks,
Anatolij