Re: [RESEND PATCH v2 4/8] mfd: stm32-timers: add support for dmas

Lee Jones
2018-03-28T15:22:51Z

On Wed, 14 Feb 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 add routine to implement burst reads using DMA from timer registers.
> This is exported. So, it can be used by child drivers, PWM capture
> for instance (but not limited to).
>
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
> Reviewed-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
> ---
> Changes in v2:
> - Abstract DMA handling from child driver: move it to MFD core
> - Add comments on optional dma support
> ---
> drivers/mfd/stm32-timers.c | 215 ++++++++++++++++++++++++++++++++++++++-
> include/linux/mfd/stm32-timers.h | 27 +++++
> 2 files changed, 238 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/mfd/stm32-timers.c b/drivers/mfd/stm32-timers.c
> index a6675a4..2cdad2c 100644
> --- a/drivers/mfd/stm32-timers.c
> +++ b/drivers/mfd/stm32-timers.c
> @@ -6,16 +6,166 @@
> * License terms: GNU General Public License (GPL), version 2
> */
>
> +#include <linux/bitfield.h>
> +#include <linux/dmaengine.h>
> +#include <linux/dma-mapping.h>
> #include <linux/mfd/stm32-timers.h>
> #include <linux/module.h>
> #include <linux/of_platform.h>
> #include <linux/reset.h>
>
> +#define STM32_TIMERS_MAX_REGISTERS 0x3fc
> +
> +struct stm32_timers_priv {
> + struct device *dev;
> + struct completion completion;
> + phys_addr_t phys_base; /* timers physical addr for dma */
> + struct mutex lock; /* protect dma access */
> + struct dma_chan *dma_chan; /* dma channel in use */

I think kerneldoc would be better than inline comments.

> + struct dma_chan *dmas[STM32_TIMERS_MAX_DMAS];
> + struct stm32_timers ddata;

This looks odd to me. Why can't you expand the current ddata
structure? Wouldn't it be better to create a stm32_timers_dma
structure to place all this information in (except *dev, that should
live in the ddata struct), then place a reference in the existing
stm32_timers struct?

> +};
> +
> +static struct stm32_timers_priv *to_stm32_timers_priv(struct stm32_timers *d)
> +{
> + return container_of(d, struct stm32_timers_priv, ddata);
> +}

If you take my other suggestions, you can remove this function.

> +/* DIER register DMA enable bits */
> +static const u32 stm32_timers_dier_dmaen[STM32_TIMERS_MAX_DMAS] = {
> + TIM_DIER_CC1DE, TIM_DIER_CC2DE, TIM_DIER_CC3DE, TIM_DIER_CC4DE,
> + TIM_DIER_UIE, TIM_DIER_TDE, TIM_DIER_COMDE
> +};

Maybe one per line would be kinder on the eye?

> +static void stm32_timers_dma_done(void *p)
> +{
> + struct stm32_timers_priv *priv = p;
> + struct dma_chan *dma_chan = priv->dma_chan;
> + struct dma_tx_state state;
> + enum dma_status status;
> +
> + status = dmaengine_tx_status(dma_chan, dma_chan->cookie, &state);
> + if (status == DMA_COMPLETE)
> + complete(&priv->completion);
> +}
> +
> +/**
> + * stm32_timers_dma_burst_read - Read from timers registers using DMA.
> + *
> + * Read from STM32 timers registers using DMA on a single event.
> + * @ddata: reference to stm32_timers

It's odd to pass device data back like this.

Better to pass a pointer to 'struct device', then use the normal
helpers.

> + * @buf: dma'able destination buffer
> + * @id: stm32_timers_dmas event identifier (ch[1..4], up, trig or com)
> + * @reg: registers start offset for DMA to read from (like CCRx for capture)
> + * @num_reg: number of registers to read upon each dma request, starting @reg.
> + * @bursts: number of bursts to read (e.g. like two for pwm period capture)
> + * @tmo_ms: timeout (milliseconds)
> + */
> +int stm32_timers_dma_burst_read(struct stm32_timers *ddata, u32 *buf,
> + enum stm32_timers_dmas id, u32 reg,
> + unsigned int num_reg, unsigned int bursts,
> + unsigned long tmo_ms)
> +{
> + struct stm32_timers_priv *priv = to_stm32_timers_priv(ddata);
> + unsigned long timeout = msecs_to_jiffies(tmo_ms);
> + struct regmap *regmap = priv->ddata.regmap;
> + size_t len = num_reg * bursts * sizeof(u32);
> + struct dma_async_tx_descriptor *desc;
> + struct dma_slave_config config;
> + dma_cookie_t cookie;
> + dma_addr_t dma_buf;
> + u32 dbl, dba;
> + long err;
> + int ret;
> +
> + /* sanity check */
> + if (id < STM32_TIMERS_DMA_CH1 || id >= STM32_TIMERS_MAX_DMAS)
> + return -EINVAL;
> +
> + if (!num_reg || !bursts || reg > STM32_TIMERS_MAX_REGISTERS ||
> + (reg + num_reg * sizeof(u32)) > STM32_TIMERS_MAX_REGISTERS)
> + return -EINVAL;
> +
> + if (!priv->dmas[id])
> + return -ENODEV;
> + mutex_lock(&priv->lock);
> + priv->dma_chan = priv->dmas[id];
> +
> + dma_buf = dma_map_single(priv->dev, buf, len, DMA_FROM_DEVICE);
> + ret = dma_mapping_error(priv->dev, dma_buf);
> + if (ret)
> + goto unlock;
> +
> + /* Prepare DMA read from timer registers, using DMA burst mode */
> + memset(&config, 0, sizeof(config));
> + config.src_addr = (dma_addr_t)priv->phys_base + TIM_DMAR;
> + config.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
> + ret = dmaengine_slave_config(priv->dma_chan, &config);
> + if (ret)
> + goto unmap;
> +
> + desc = dmaengine_prep_slave_single(priv->dma_chan, dma_buf, len,
> + DMA_DEV_TO_MEM, DMA_PREP_INTERRUPT);
> + if (!desc) {
> + ret = -EBUSY;
> + goto unmap;
> + }
> +
> + desc->callback = stm32_timers_dma_done;
> + desc->callback_param = priv;
> + cookie = dmaengine_submit(desc);
> + ret = dma_submit_error(cookie);
> + if (ret)
> + goto dma_term;
> +
> + reinit_completion(&priv->completion);
> + dma_async_issue_pending(priv->dma_chan);
> +
> + /* Setup and enable timer DMA burst mode */
> + dbl = FIELD_PREP(TIM_DCR_DBL, bursts - 1);
> + dba = FIELD_PREP(TIM_DCR_DBA, reg >> 2);
> + ret = regmap_write(regmap, TIM_DCR, dbl | dba);
> + if (ret)
> + goto dma_term;
> +
> + /* Clear pending flags before enabling DMA request */
> + ret = regmap_write(regmap, TIM_SR, 0);
> + if (ret)
> + goto dcr_clr;
> +
> + ret = regmap_update_bits(regmap, TIM_DIER, stm32_timers_dier_dmaen[id],
> + stm32_timers_dier_dmaen[id]);
> + if (ret)
> + goto dcr_clr;
> +
> + err = wait_for_completion_interruptible_timeout(&priv->completion,
> + timeout);
> + if (err == 0)
> + ret = -ETIMEDOUT;
> + else if (err < 0)
> + ret = err;
> +
> + regmap_update_bits(regmap, TIM_DIER, stm32_timers_dier_dmaen[id], 0);
> + regmap_write(regmap, TIM_SR, 0);
> +dcr_clr:
> + regmap_write(regmap, TIM_DCR, 0);
> +dma_term:
> + dmaengine_terminate_all(priv->dma_chan);
> +unmap:
> + dma_unmap_single(priv->dev, dma_buf, len, DMA_FROM_DEVICE);
> +unlock:
> + priv->dma_chan = NULL;
> + mutex_unlock(&priv->lock);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(stm32_timers_dma_burst_read);
> +
> static const struct regmap_config stm32_timers_regmap_cfg = {
> .reg_bits = 32,
> .val_bits = 32,
> .reg_stride = sizeof(u32),
> - .max_register = 0x3fc,
> + .max_register = STM32_TIMERS_MAX_REGISTERS,
> };
>
> static void stm32_timers_get_arr_size(struct stm32_timers *ddata)
> @@ -29,21 +179,55 @@ 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_priv *priv)
> +{
> + int i;
> + char name[4];
> + struct dma_chan **dmas = priv->dmas;
> +
> + /* Optional DMA support: get valid dma channel(s) or NULL */
> + for (i = STM32_TIMERS_DMA_CH1; i <= STM32_TIMERS_DMA_CH4; i++) {
> + snprintf(name, ARRAY_SIZE(name), "ch%1d", i + 1);
> + dmas[i] = dma_request_slave_channel(dev, name);
> + }
> + dmas[STM32_TIMERS_DMA_UP] = dma_request_slave_channel(dev, "up");
> + dmas[STM32_TIMERS_DMA_TRIG] = dma_request_slave_channel(dev, "trig");
> + dmas[STM32_TIMERS_DMA_COM] = dma_request_slave_channel(dev, "com");
> +}
> +
> +static void stm32_timers_dma_remove(struct device *dev,
> + struct stm32_timers_priv *priv)
> +{
> + int i;
> +
> + for (i = STM32_TIMERS_DMA_CH1; i < STM32_TIMERS_MAX_DMAS; i++)
> + if (priv->dmas[i])
> + dma_release_channel(priv->dmas[i]);
> +}
> +
> static int stm32_timers_probe(struct platform_device *pdev)
> {
> struct device *dev = &pdev->dev;
> + struct stm32_timers_priv *priv;
> struct stm32_timers *ddata;
> struct resource *res;
> void __iomem *mmio;
> + int ret;
>
> - ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
> - if (!ddata)
> + priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> + if (!priv)
> return -ENOMEM;
> + ddata = &priv->ddata;
> + init_completion(&priv->completion);
> + mutex_init(&priv->lock);
> + priv->dev = dev;
>
> res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> mmio = devm_ioremap_resource(dev, res);
> if (IS_ERR(mmio))
> return PTR_ERR(mmio);
> + priv->phys_base = res->start;
>
> ddata->regmap = devm_regmap_init_mmio_clk(dev, "int", mmio,
> &stm32_timers_regmap_cfg);
> @@ -56,9 +240,31 @@ static int stm32_timers_probe(struct platform_device *pdev)
>
> stm32_timers_get_arr_size(ddata);
>
> + stm32_timers_dma_probe(dev, priv);
> +
> platform_set_drvdata(pdev, ddata);
>
> - return devm_of_platform_populate(&pdev->dev);
> + ret = of_platform_populate(pdev->dev.of_node, NULL, NULL, &pdev->dev);
> + if (ret)
> + goto dma_remove;
> +
> + return 0;
> +
> +dma_remove:
> + stm32_timers_dma_remove(dev, priv);

You can easily remove this label and the goto.

> + return ret;
> +}
> +
> +static int stm32_timers_remove(struct platform_device *pdev)
> +{
> + struct stm32_timers *ddata = platform_get_drvdata(pdev);
> + struct stm32_timers_priv *priv = to_stm32_timers_priv(ddata);
> +
> + of_platform_depopulate(&pdev->dev);

Why can't you continue using devm_*?

> + stm32_timers_dma_remove(&pdev->dev, priv);
> +
> + return 0;
> }
>
> static const struct of_device_id stm32_timers_of_match[] = {
> @@ -69,6 +275,7 @@ 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..5fd2d6b 100644
> --- a/include/linux/mfd/stm32-timers.h
> +++ b/include/linux/mfd/stm32-timers.h
> @@ -29,6 +29,8 @@
> #define TIM_CCR3 0x3C /* Capt/Comp Register 3 */
> #define TIM_CCR4 0x40 /* Capt/Comp Register 4 */
> #define TIM_BDTR 0x44 /* Break and Dead-Time Reg */
> +#define TIM_DCR 0x48 /* DMA control register */
> +#define TIM_DMAR 0x4C /* DMA register for transfer */
>
> #define TIM_CR1_CEN BIT(0) /* Counter Enable */
> #define TIM_CR1_DIR BIT(4) /* Counter Direction */
> @@ -38,6 +40,13 @@
> #define TIM_SMCR_SMS (BIT(0) | BIT(1) | BIT(2)) /* Slave mode selection */
> #define TIM_SMCR_TS (BIT(4) | BIT(5) | BIT(6)) /* Trigger selection */
> #define TIM_DIER_UIE BIT(0) /* Update interrupt */
> +#define TIM_DIER_UDE BIT(8) /* Update DMA request Enable */
> +#define TIM_DIER_CC1DE BIT(9) /* CC1 DMA request Enable */
> +#define TIM_DIER_CC2DE BIT(10) /* CC2 DMA request Enable */
> +#define TIM_DIER_CC3DE BIT(11) /* CC3 DMA request Enable */
> +#define TIM_DIER_CC4DE BIT(12) /* CC4 DMA request Enable */
> +#define TIM_DIER_COMDE BIT(13) /* COM DMA request Enable */
> +#define TIM_DIER_TDE BIT(14) /* Trigger DMA request Enable */
> #define TIM_SR_UIF BIT(0) /* Update interrupt flag */
> #define TIM_EGR_UG BIT(0) /* Update Generation */
> #define TIM_CCMR_PE BIT(3) /* Channel Preload Enable */
> @@ -58,6 +67,8 @@
> #define TIM_BDTR_BK2F (BIT(20) | BIT(21) | BIT(22) | BIT(23))
> #define TIM_BDTR_BK2E BIT(24) /* Break 2 input enable */
> #define TIM_BDTR_BK2P BIT(25) /* Break 2 input polarity */
> +#define TIM_DCR_DBA GENMASK(4, 0) /* DMA base addr */
> +#define TIM_DCR_DBL GENMASK(12, 8) /* DMA burst len */
>
> #define MAX_TIM_PSC 0xFFFF
> #define TIM_CR2_MMS_SHIFT 4
> @@ -67,9 +78,25 @@
> #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;
> u32 max_arr;
> };
> +
> +int stm32_timers_dma_burst_read(struct stm32_timers *ddata, u32 *buf,
> + enum stm32_timers_dmas id, u32 reg,
> + unsigned int num_reg, unsigned int bursts,
> + unsigned long tmo_ms);
> #endif

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