linux-kernel - Re: [PATCH 4/8] mfd: stm32-timers: add support for dmas

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Message-ID: <20180123133234.xmep76cgdremnj47@dell>
Date:   Tue, 23 Jan 2018 13:32:34 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     Fabrice Gasnier <fabrice.gasnier@...com>
Cc:     thierry.reding@...il.com, robh+dt@...nel.org,
        alexandre.torgue@...com, benjamin.gaignard@...aro.org,
        mark.rutland@....com, linux@...linux.org.uk,
        mcoquelin.stm32@...il.com, benjamin.gaignard@...com,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-pwm@...r.kernel.org
Subject: Re: [PATCH 4/8] mfd: stm32-timers: add support for dmas

On Tue, 16 Jan 2018, Fabrice Gasnier wrote:

> STM32 Timers can support up to 7 dma requests:
> 4 channels, update, compare and trigger.
> Optionally request part, or all dmas from stm32-timers MFD core.
> Also, keep reference of device's bus address to allow child drivers to
> transfer data from/to device by using dma.
> 
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...com>
> ---
>  drivers/mfd/stm32-timers.c       | 37 ++++++++++++++++++++++++++++++++++++-
>  include/linux/mfd/stm32-timers.h | 14 ++++++++++++++
>  2 files changed, 50 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mfd/stm32-timers.c b/drivers/mfd/stm32-timers.c
> index a6675a4..372b51e 100644
> --- a/drivers/mfd/stm32-timers.c
> +++ b/drivers/mfd/stm32-timers.c
> @@ -29,6 +29,23 @@ static void stm32_timers_get_arr_size(struct stm32_timers *ddata)
>  	regmap_write(ddata->regmap, TIM_ARR, 0x0);
>  }
>  
> +static void stm32_timers_dma_probe(struct device *dev,
> +				   struct stm32_timers *ddata)
> +{
> +	int i;
> +	char name[4];
> +
> +	for (i = STM32_TIMERS_DMA_CH1; i <= STM32_TIMERS_DMA_CH4; i++) {
> +		snprintf(name, ARRAY_SIZE(name), "ch%1d", i + 1);
> +		ddata->dmas[i] = dma_request_slave_channel(dev, name);

And if any of them fail?

> +	}
> +	ddata->dmas[STM32_TIMERS_DMA_UP] = dma_request_slave_channel(dev, "up");
> +	ddata->dmas[STM32_TIMERS_DMA_TRIG] =
> +		dma_request_slave_channel(dev, "trig");
> +	ddata->dmas[STM32_TIMERS_DMA_COM] =
> +		dma_request_slave_channel(dev, "com");

Can you format these in the same why.  This hurts my eyes.

> +}
> +
>  static int stm32_timers_probe(struct platform_device *pdev)
>  {
>  	struct device *dev = &pdev->dev;
> @@ -44,6 +61,7 @@ static int stm32_timers_probe(struct platform_device *pdev)
>  	mmio = devm_ioremap_resource(dev, res);
>  	if (IS_ERR(mmio))
>  		return PTR_ERR(mmio);
> +	ddata->phys_base = res->start;

What do you use this for?

>  	ddata->regmap = devm_regmap_init_mmio_clk(dev, "int", mmio,
>  						  &stm32_timers_regmap_cfg);
> @@ -56,9 +74,25 @@ static int stm32_timers_probe(struct platform_device *pdev)
>  
>  	stm32_timers_get_arr_size(ddata);
>  
> +	stm32_timers_dma_probe(dev, ddata);
> +

Surely this can fail?

>  	platform_set_drvdata(pdev, ddata);
>  
> -	return devm_of_platform_populate(&pdev->dev);
> +	return of_platform_populate(pdev->dev.of_node, NULL, NULL, &pdev->dev);
> +}
> +
> +static int stm32_timers_remove(struct platform_device *pdev)
> +{
> +	struct stm32_timers *ddata = platform_get_drvdata(pdev);
> +	int i;
> +
> +	of_platform_depopulate(&pdev->dev);
> +
> +	for (i = 0; i < STM32_TIMERS_MAX_DMAS; i++)
> +		if (ddata->dmas[i])
> +			dma_release_channel(ddata->dmas[i]);
> +
> +	return 0;
>  }
>  
>  static const struct of_device_id stm32_timers_of_match[] = {
> @@ -69,6 +103,7 @@ static int stm32_timers_probe(struct platform_device *pdev)
>  
>  static struct platform_driver stm32_timers_driver = {
>  	.probe = stm32_timers_probe,
> +	.remove = stm32_timers_remove,
>  	.driver	= {
>  		.name = "stm32-timers",
>  		.of_match_table = stm32_timers_of_match,
> diff --git a/include/linux/mfd/stm32-timers.h b/include/linux/mfd/stm32-timers.h
> index ce7346e..2b4ffb9 100644
> --- a/include/linux/mfd/stm32-timers.h
> +++ b/include/linux/mfd/stm32-timers.h
> @@ -10,6 +10,7 @@
>  #define _LINUX_STM32_GPTIMER_H_
>  
>  #include <linux/clk.h>
> +#include <linux/dmaengine.h>
>  #include <linux/regmap.h>
>  
>  #define TIM_CR1		0x00	/* Control Register 1      */
> @@ -67,9 +68,22 @@
>  #define TIM_BDTR_BKF_SHIFT	16
>  #define TIM_BDTR_BK2F_SHIFT	20
>  
> +enum stm32_timers_dmas {
> +	STM32_TIMERS_DMA_CH1,
> +	STM32_TIMERS_DMA_CH2,
> +	STM32_TIMERS_DMA_CH3,
> +	STM32_TIMERS_DMA_CH4,
> +	STM32_TIMERS_DMA_UP,
> +	STM32_TIMERS_DMA_TRIG,
> +	STM32_TIMERS_DMA_COM,
> +	STM32_TIMERS_MAX_DMAS,
> +};
> +
>  struct stm32_timers {
>  	struct clk *clk;
>  	struct regmap *regmap;
> +	phys_addr_t phys_base;
>  	u32 max_arr;
> +	struct dma_chan *dmas[STM32_TIMERS_MAX_DMAS];
>  };
>  #endif

-- 
Lee Jones
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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