Re: [PATCH 3/3] spi: stm32-qspi: add automatic poll status feature

[Boris Brezillon]

On Mon, 26 Apr 2021 16:39:34 +0200
<patrice.chotard@xxxxxxxxxxx> wrote:

> From: Christophe Kerello <christophe.kerello@xxxxxxxxxxx>
> 
> STM32 QSPI is able to automatically poll a specified register inside the
> memory and relieve the CPU from this task.
> 
> As example, when erasing a large memory area, we got cpu load
> equal to 50%.

Ouch! I feel like this should be fixed at the core level too so we
don't poll the status so frequently, or at least wait a bit before
polling the status (especially for erase/write operations).

> This patch allows to perform the same operation
> with a cpu load around 2%.
> 
> Signed-off-by: Christophe Kerello <christophe.kerello@xxxxxxxxxxx>
> Signed-off-by: Patrice Chotard <patrice.chotard@xxxxxxxxxxx>
> ---
>  drivers/spi/spi-stm32-qspi.c | 80 ++++++++++++++++++++++++++++++++----
>  1 file changed, 72 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/spi/spi-stm32-qspi.c b/drivers/spi/spi-stm32-qspi.c
> index 7e640ccc7e77..2f9e5941f14f 100644
> --- a/drivers/spi/spi-stm32-qspi.c
> +++ b/drivers/spi/spi-stm32-qspi.c
> @@ -36,6 +36,7 @@
>  #define CR_FTIE			BIT(18)
>  #define CR_SMIE			BIT(19)
>  #define CR_TOIE			BIT(20)
> +#define CR_APMS			BIT(22)
>  #define CR_PRESC_MASK		GENMASK(31, 24)
>  
>  #define QSPI_DCR		0x04
> @@ -53,6 +54,7 @@
>  #define QSPI_FCR		0x0c
>  #define FCR_CTEF		BIT(0)
>  #define FCR_CTCF		BIT(1)
> +#define FCR_CSMF		BIT(3)
>  
>  #define QSPI_DLR		0x10
>  
> @@ -107,6 +109,7 @@ struct stm32_qspi {
>  	u32 clk_rate;
>  	struct stm32_qspi_flash flash[STM32_QSPI_MAX_NORCHIP];
>  	struct completion data_completion;
> +	struct completion match_completion;
>  	u32 fmode;
>  
>  	struct dma_chan *dma_chtx;
> @@ -115,6 +118,7 @@ struct stm32_qspi {
>  
>  	u32 cr_reg;
>  	u32 dcr_reg;
> +	u16 status_timeout;
>  
>  	/*
>  	 * to protect device configuration, could be different between
> @@ -128,11 +132,20 @@ static irqreturn_t stm32_qspi_irq(int irq, void *dev_id)
>  	struct stm32_qspi *qspi = (struct stm32_qspi *)dev_id;
>  	u32 cr, sr;
>  
> +	cr = readl_relaxed(qspi->io_base + QSPI_CR);
>  	sr = readl_relaxed(qspi->io_base + QSPI_SR);
>  
> +	if (cr & CR_SMIE && sr & SR_SMF) {
> +		/* disable irq */
> +		cr &= ~CR_SMIE;
> +		writel_relaxed(cr, qspi->io_base + QSPI_CR);
> +		complete(&qspi->match_completion);
> +
> +		return IRQ_HANDLED;
> +	}
> +
>  	if (sr & (SR_TEF | SR_TCF)) {
>  		/* disable irq */
> -		cr = readl_relaxed(qspi->io_base + QSPI_CR);
>  		cr &= ~CR_TCIE & ~CR_TEIE;
>  		writel_relaxed(cr, qspi->io_base + QSPI_CR);
>  		complete(&qspi->data_completion);
> @@ -319,6 +332,24 @@ static int stm32_qspi_wait_cmd(struct stm32_qspi *qspi,
>  	return err;
>  }
>  
> +static int stm32_qspi_wait_poll_status(struct stm32_qspi *qspi,
> +				       const struct spi_mem_op *op)
> +{
> +	u32 cr;
> +
> +	reinit_completion(&qspi->match_completion);
> +	cr = readl_relaxed(qspi->io_base + QSPI_CR);
> +	writel_relaxed(cr | CR_SMIE, qspi->io_base + QSPI_CR);
> +
> +	if (!wait_for_completion_timeout(&qspi->match_completion,
> +				msecs_to_jiffies(qspi->status_timeout)))
> +		return -ETIMEDOUT;
> +
> +	writel_relaxed(FCR_CSMF, qspi->io_base + QSPI_FCR);
> +
> +	return 0;
> +}
> +
>  static int stm32_qspi_get_mode(struct stm32_qspi *qspi, u8 buswidth)
>  {
>  	if (buswidth == 4)
> @@ -332,7 +363,7 @@ static int stm32_qspi_send(struct spi_mem *mem, const struct spi_mem_op *op)
>  	struct stm32_qspi *qspi = spi_controller_get_devdata(mem->spi->master);
>  	struct stm32_qspi_flash *flash = &qspi->flash[mem->spi->chip_select];
>  	u32 ccr, cr;
> -	int timeout, err = 0;
> +	int timeout, err = 0, err_poll_status = 0;
>  
>  	dev_dbg(qspi->dev, "cmd:%#x mode:%d.%d.%d.%d addr:%#llx len:%#x\n",
>  		op->cmd.opcode, op->cmd.buswidth, op->addr.buswidth,
> @@ -378,6 +409,9 @@ static int stm32_qspi_send(struct spi_mem *mem, const struct spi_mem_op *op)
>  	if (op->addr.nbytes && qspi->fmode != CCR_FMODE_MM)
>  		writel_relaxed(op->addr.val, qspi->io_base + QSPI_AR);
>  
> +	if (qspi->fmode == CCR_FMODE_APM)
> +		err_poll_status = stm32_qspi_wait_poll_status(qspi, op);
> +
>  	err = stm32_qspi_tx(qspi, op);
>  
>  	/*
> @@ -387,7 +421,7 @@ static int stm32_qspi_send(struct spi_mem *mem, const struct spi_mem_op *op)
>  	 *  byte of device (device size - fifo size). like device size is not
>  	 *  knows, the prefetching is always stop.
>  	 */
> -	if (err || qspi->fmode == CCR_FMODE_MM)
> +	if (err || err_poll_status || qspi->fmode == CCR_FMODE_MM)
>  		goto abort;
>  
>  	/* wait end of tx in indirect mode */
> @@ -406,15 +440,43 @@ static int stm32_qspi_send(struct spi_mem *mem, const struct spi_mem_op *op)
>  						    cr, !(cr & CR_ABORT), 1,
>  						    STM32_ABT_TIMEOUT_US);
>  
> -	writel_relaxed(FCR_CTCF, qspi->io_base + QSPI_FCR);
> +	writel_relaxed(FCR_CTCF | FCR_CSMF, qspi->io_base + QSPI_FCR);
>  
> -	if (err || timeout)
> -		dev_err(qspi->dev, "%s err:%d abort timeout:%d\n",
> -			__func__, err, timeout);
> +	if (err || err_poll_status || timeout)
> +		dev_err(qspi->dev, "%s err:%d err_poll_status:%d abort timeout:%d\n",
> +			__func__, err, err_poll_status, timeout);
>  
>  	return err;
>  }
>  
> +static int stm32_qspi_poll_status(struct spi_mem *mem, const struct spi_mem_op *op,
> +				  u8 mask, u8 match, u16 timeout_ms)
> +{
> +	struct stm32_qspi *qspi = spi_controller_get_devdata(mem->spi->master);
> +	int ret;
> +
> +	ret = pm_runtime_get_sync(qspi->dev);
> +	if (ret < 0) {
> +		pm_runtime_put_noidle(qspi->dev);
> +		return ret;
> +	}
> +
> +	mutex_lock(&qspi->lock);
> +
> +	writel_relaxed(mask, qspi->io_base + QSPI_PSMKR);
> +	writel_relaxed(match, qspi->io_base + QSPI_PSMAR);
> +	qspi->fmode = CCR_FMODE_APM;
> +	qspi->status_timeout = timeout_ms;
> +
> +	ret = stm32_qspi_send(mem, op);
> +	mutex_unlock(&qspi->lock);
> +
> +	pm_runtime_mark_last_busy(qspi->dev);
> +	pm_runtime_put_autosuspend(qspi->dev);
> +
> +	return ret;
> +}
> +
>  static int stm32_qspi_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
>  {
>  	struct stm32_qspi *qspi = spi_controller_get_devdata(mem->spi->master);
> @@ -527,7 +589,7 @@ static int stm32_qspi_setup(struct spi_device *spi)
>  	flash->presc = presc;
>  
>  	mutex_lock(&qspi->lock);
> -	qspi->cr_reg = 3 << CR_FTHRES_SHIFT | CR_SSHIFT | CR_EN;
> +	qspi->cr_reg = CR_APMS | 3 << CR_FTHRES_SHIFT | CR_SSHIFT | CR_EN;
>  	writel_relaxed(qspi->cr_reg, qspi->io_base + QSPI_CR);
>  
>  	/* set dcr fsize to max address */
> @@ -607,6 +669,7 @@ static const struct spi_controller_mem_ops stm32_qspi_mem_ops = {
>  	.exec_op	= stm32_qspi_exec_op,
>  	.dirmap_create	= stm32_qspi_dirmap_create,
>  	.dirmap_read	= stm32_qspi_dirmap_read,
> +	.poll_status	= stm32_qspi_poll_status,
>  };
>  
>  static int stm32_qspi_probe(struct platform_device *pdev)
> @@ -661,6 +724,7 @@ static int stm32_qspi_probe(struct platform_device *pdev)
>  	}
>  
>  	init_completion(&qspi->data_completion);
> +	init_completion(&qspi->match_completion);
>  
>  	qspi->clk = devm_clk_get(dev, NULL);
>  	if (IS_ERR(qspi->clk)) {