linux-kernel - Re: [PATCH v2 2/4] spi: rockchip: add support for "cs-gpios" dts property

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Message-ID: <20170613173346.GB9026@google.com>
Date:   Tue, 13 Jun 2017 10:33:46 -0700
From:   Brian Norris <briannorris@...omium.org>
To:     Jeffy Chen <jeffy.chen@...k-chips.com>
Cc:     linux-kernel@...r.kernel.org, broonie@...nel.org,
        dianders@...omium.org, heiko@...ech.de, linux-spi@...r.kernel.org,
        linux-rockchip@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 2/4] spi: rockchip: add support for "cs-gpios" dts
 property

Hi Jeffy,

On Tue, Jun 13, 2017 at 01:25:41PM +0800, Jeffy Chen wrote:
> Support using "cs-gpios" property to specify cs gpios.
> 
> Signed-off-by: Jeffy Chen <jeffy.chen@...k-chips.com>
> 1/ request cs gpios in probe for better error handling
> 2/ use gpiod* function
> (suggested by Heiko Stuebner)
> 
> 3/ split dt-binding changes to new patch
> (suggested by Shawn Lin & Heiko Stuebner)
> 
> ---
> 
> Changes in v2: None
> 
>  drivers/spi/spi-rockchip.c | 30 +++++++++++++++++++++++++++++-
>  1 file changed, 29 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/spi/spi-rockchip.c b/drivers/spi/spi-rockchip.c
> index bab9b13..ad8997b 100644
> --- a/drivers/spi/spi-rockchip.c
> +++ b/drivers/spi/spi-rockchip.c
> @@ -16,7 +16,7 @@
>  #include <linux/clk.h>
>  #include <linux/dmaengine.h>
>  #include <linux/module.h>
> -#include <linux/of.h>
> +#include <linux/of_gpio.h>
>  #include <linux/pinctrl/consumer.h>
>  #include <linux/platform_device.h>
>  #include <linux/spi/spi.h>
> @@ -663,6 +663,27 @@ static bool rockchip_spi_can_dma(struct spi_master *master,
>  	return (xfer->len > rs->fifo_len);
>  }
>  
> +static int rockchip_spi_setup_cs_gpios(struct device *dev)
> +{
> +	struct device_node *np = dev->of_node;
> +	struct gpio_desc *cs_gpio;
> +	int i, nb;
> +
> +	if (!np)
> +		return 0;
> +
> +	nb = of_gpio_named_count(np, "cs-gpios");
> +	for (i = 0; i < nb; i++) {
> +		/* We support both GPIO CS and HW CS */
> +		cs_gpio = devm_gpiod_get_index_optional(dev, "cs",
> +							i, GPIOD_ASIS);
> +		if (IS_ERR(cs_gpio))
> +			return PTR_ERR(cs_gpio);

I'm a bit confused why you need this function at all. You aren't using
the references that you're grabbing here, so essentially this is just
error-checking.

Are you doing anything here that isn't covered in
of_spi_register_master()?

> +	}
> +
> +	return 0;
> +}
> +
>  static int rockchip_spi_probe(struct platform_device *pdev)
>  {
>  	int ret = 0;
> @@ -749,6 +770,7 @@ static int rockchip_spi_probe(struct platform_device *pdev)
>  	master->transfer_one = rockchip_spi_transfer_one;
>  	master->max_transfer_size = rockchip_spi_max_transfer_size;
>  	master->handle_err = rockchip_spi_handle_err;
> +	master->flags = SPI_MASTER_GPIO_SS;

I'm curious, do you actually need to assert both the HW and GPIO CS?

Brian

>  
>  	rs->dma_tx.ch = dma_request_chan(rs->dev, "tx");
>  	if (IS_ERR(rs->dma_tx.ch)) {
> @@ -783,6 +805,12 @@ static int rockchip_spi_probe(struct platform_device *pdev)
>  		master->dma_rx = rs->dma_rx.ch;
>  	}
>  
> +	ret = rockchip_spi_setup_cs_gpios(&pdev->dev);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Failed to setup cs gpios\n");
> +		goto err_free_dma_rx;
> +	}
> +
>  	ret = devm_spi_register_master(&pdev->dev, master);
>  	if (ret) {
>  		dev_err(&pdev->dev, "Failed to register master\n");
> -- 
> 2.1.4
> 
>