linux-kernel - Re: [PATCH v2 6/6] serial: exar: Add support for IOT2040 device

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Date:   Thu, 18 May 2017 18:39:50 +0200
From:   Jan Kiszka <jan.kiszka@...mens.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Alexandre Courbot <gnurou@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        Sudip Mukherjee <sudip.mukherjee@...ethink.co.uk>,
        Sascha Weisenberger <sascha.weisenberger@...mens.com>
Subject: Re: [PATCH v2 6/6] serial: exar: Add support for IOT2040 device

On 2017-05-18 18:33, Andy Shevchenko wrote:
> On Thu, May 18, 2017 at 5:59 PM, Jan Kiszka <jan.kiszka@...mens.com> wrote:
>> This implements the setup of RS232 and the switch-over to RS485 or RS422
>> for the Siemens IOT2040. That uses an EXAR XR17V352 with external logic
>> to switch between the different modes. The external logic is controlled
>> via MPIO pins of the EXAR controller.
>>
>> Only pin 10 can be exported as GPIO on the IOT2040. It is connected to
>> an LED.
>>
>> As the XR17V352 used on the IOT2040 is not equipped with an external
>> EEPROM, it cannot present itself as IOT2040-variant via subvendor/
>> subdevice IDs. Thus, we have to check via DMI for the target platform.
>>
>> Co-developed with Sascha Weisenberger.
> 
> Few nits below and one comment that should be addressed.
> 
>> +#define UART_EXAR_RS485_DLY(x) (x << 4)
> 
> ((x) << 4)

Yep.

> 
>> +static bool is_iot2040;
> 
> No, please, use driver data of DMI and hide this in corresponding structure.
> Or even assign  port->port.rs485_config in the callback function.
> 
> Moreover, can't you use port->port.rs485_config != NULL instead?

There are two cases to be handled on IOT2040: the setting of the
rs485_config and the different setup of the GPIOs, but the latter at a
specific point in the initialization only. So I don't see yet how
driver_data could come into play and help.

> 
>> +
>>  struct exar8250;
>>
>>  /**
>> @@ -212,6 +252,82 @@ xr17v35x_register_gpio(struct pci_dev *pcidev, unsigned int first_gpio,
>>         return pdev;
>>  }
>>
>> +static int iot2040_rs485_config(struct uart_port *port,
>> +                               struct serial_rs485 *rs485)
>> +{
>> +       u8 __iomem *p = port->membase;
>> +       u8 mask = IOT2040_UART1_MASK;
>> +       u8 mode, value;
> 
>> +       bool is_rs485 = false;
>> +
>> +       if (rs485->flags & SER_RS485_ENABLED) {
>> +               is_rs485 = true;
> 
> bool is_rs485 = !!(rs485->flags & SER_RS485_ENABLED);
> 
> if (is_rs485) {
> ...
> } else {
> ...
> }
> 

OK.

>> +       return 0;
>> +}
> 
>> +static int iot2040_match(const struct dmi_system_id *dmi)
>> +{
>> +       is_iot2040 = true;
>> +       return 1;
>> +}
> 
> See above.

See above.

Jan

> 
>> +
>> +static const struct dmi_system_id exar_platforms[] = {
>> +       {
>> +               .callback = iot2040_match,
>> +               .ident = "IOT2040",
>> +               .matches = {
>> +                       DMI_MATCH(DMI_BOARD_NAME, "SIMATIC IOT2000"),
>> +                       DMI_MATCH(DMI_BOARD_ASSET_TAG, "6ES7647-0AA00-1YA2"),
>> +               },
>> +       }
>> +};
>