linux-kernel - Re: [PATCH v4 5/6] spi: at91-usart: add driver for at91-usart as spi

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Date:   Mon, 28 May 2018 11:21:26 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Radu Pirea <radu.pirea@...rochip.com>
Cc:     Mark Brown <broonie@...nel.org>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        alexandre.belloni@...tlin.com, Lee Jones <lee.jones@...aro.org>,
        Richard Genoud <richard.genoud@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-spi <linux-spi@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>
Subject: Re: [PATCH v4 5/6] spi: at91-usart: add driver for at91-usart as spi

On Fri, May 25, 2018 at 8:19 PM, Radu Pirea <radu.pirea@...rochip.com> wrote:
> This is the driver for at91-usart in spi mode. The USART IP can be configured
> to work in many modes and one of them is SPI.
>
> The driver was tested on sama5d3-xplained and sama5d4-xplained boards with
> enc28j60 ethernet controller as slave.

> +#include <linux/of_gpio.h>

What is the use of it?

> +#define US_INIT                        (US_MR_SPI_MASTER | US_MR_CHRL | US_MR_CLKO | \
> +                               US_MR_WRDBT)

Don't split lines like this, it's hard to read.

#define FOO \
 (BAR1 | BAR2)

I think I already told this to someone recently, maybe to you.

> +/* Register access macros */
> +#define spi_readl(port, reg) \
> +       readl_relaxed((port)->regs + US_##reg)
> +#define spi_writel(port, reg, value) \
> +       writel_relaxed((value), (port)->regs + US_##reg)
> +
> +#define spi_readb(port, reg) \
> +       readb_relaxed((port)->regs + US_##reg)
> +#define spi_writeb(port, reg, value) \
> +       writeb_relaxed((value), (port)->regs + US_##reg)

Names are too generic. You better to use the same prefix as for the
rest, i.e. at91_spi_

> +       /*used in interrupt to protect data reading*/

Comment style.

You need to read some existing code, perhaps, to see how it's done.

> +static inline void at91_usart_spi_tx(struct at91_usart_spi *aus)
> +{
> +       unsigned int len = aus->current_transfer->len;
> +       unsigned int remaining = aus->current_tx_remaining_bytes;
> +       const u8  *tx_buf = aus->current_transfer->tx_buf;
> +

> +       if (remaining)
> +               if (at91_usart_spi_tx_ready(aus)) {

if (x) {
 if (y) {
...
 }
}

is equivalent to if (x && y) {}.

Though, considering your intention here, I would rather go with better
pattern, i.e.

if (!remaining)
 return;

> +                       spi_writeb(aus, THR, tx_buf[len - remaining]);
> +                       aus->current_tx_remaining_bytes--;
> +               }
> +}
> +
> +static inline void at91_usart_spi_rx(struct at91_usart_spi *aus)
> +{

> +       if (remaining) {
> +               rx_buf[len - remaining] = spi_readb(aus, RHR);
> +               aus->current_rx_remaining_bytes--;
> +       }

Ditto.

> +}


> +static int at91_usart_gpio_setup(struct platform_device *pdev)
> +{

> +       struct device_node      *np = pdev->dev.parent->of_node;

Your driver is not OF specific as far as I can see. Drop all these
device_node stuff and change API calls respectively.

> +       int                     i;

> +       int                     ret = 0;
> +       int                     nb = 0;

What happened to indentation?

Redundnant assignment for both.

> +       if (!np)
> +               return -EINVAL;
> +
> +       nb = of_gpio_named_count(np, "cs-gpios");
> +       for (i = 0; i < nb; i++) {
> +               int cs_gpio = of_get_named_gpio(np, "cs-gpios", i);
> +
> +               if (cs_gpio < 0)
> +                       return cs_gpio;
> +
> +               if (gpio_is_valid(cs_gpio)) {
> +                       ret = devm_gpio_request_one(&pdev->dev, cs_gpio,
> +                                                   GPIOF_DIR_OUT,
> +                                                   dev_name(&pdev->dev));
> +                       if (ret)
> +                               return ret;
> +               }
> +       }
> +
> +       return 0;
> +}
> +
> +static int at91_usart_spi_probe(struct platform_device *pdev)
> +{

> +       regs = platform_get_resource(to_platform_device(pdev->dev.parent),
> +                                    IORESOURCE_MEM, 0);
> +       if (!regs)
> +               return -EINVAL;

This looks weird. Supply resource to _this_ device in your MFD code.

> +       dev_info(&pdev->dev,
> +                "Atmel USART SPI Controller version 0x%x at 0x%08lx (irq %d)\n",
> +                spi_readl(aus, VERSION),
> +                (unsigned long)regs->start, irq);

I think I already told you, don't use explicit casting when print.
If it wasn't you, do you homework then. But above is no go.

> +       return 0;

> +static struct platform_driver at91_usart_spi_driver = {
> +       .driver = {
> +               .name = "at91_usart_spi",

> +               .of_match_table = of_match_ptr(at91_usart_spi_dt_ids),

Drop of_match_ptr(). It's not needed.

> +       },
> +       .probe = at91_usart_spi_probe,

> +       .remove = at91_usart_spi_remove, };

Already told ya, split lines correctly.

-- 
With Best Regards,
Andy Shevchenko