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Commit 57c2ecd9 authored by Vignesh R's avatar Vignesh R Committed by Mark Brown
Browse files

spi: spi-ti-qspi: switch to polling mode for better r/w performance 



Currently word completion interrupt is fired for transfer of every
word(8bit to 128bit in size). This adds a lot of overhead, and decreases
r/w throughput. It hardly takes 3us(@48MHz) for 128bit r/w to complete,
hence its better to poll on word complete bit to be set in
QSPI_SPI_STATUS_REG instead of using interrupts.
This increases the throughput by 30% in both read and write case.

So, switch to polling mode instead of interrupts to determine completion
of word transfer.

Signed-off-by: default avatarVignesh R <vigneshr@ti.com>
Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent 6ff33f39

drivers/spi/spi-ti-qspi.c

+20 −54
Original line number Diff line number Diff line
@@ -39,8 +39,6 @@ struct ti_qspi_regs { 
};



struct ti_qspi {

	struct completion       transfer_complete;



	/* list synchronization */

	struct mutex            list_lock;
@@ -62,10 +60,6 @@ struct ti_qspi { 


#define QSPI_PID			(0x0)

#define QSPI_SYSCONFIG			(0x10)

#define QSPI_INTR_STATUS_RAW_SET	(0x20)

#define QSPI_INTR_STATUS_ENABLED_CLEAR	(0x24)

#define QSPI_INTR_ENABLE_SET_REG	(0x28)

#define QSPI_INTR_ENABLE_CLEAR_REG	(0x2c)

#define QSPI_SPI_CLOCK_CNTRL_REG	(0x40)

#define QSPI_SPI_DC_REG			(0x44)

#define QSPI_SPI_CMD_REG		(0x48)
@@ -97,7 +91,6 @@ struct ti_qspi { 
#define QSPI_RD_DUAL			(3 << 16)

#define QSPI_RD_QUAD			(7 << 16)

#define QSPI_INVAL			(4 << 16)

#define QSPI_WC_CMD_INT_EN			(1 << 14)

#define QSPI_FLEN(n)			((n - 1) << 0)

#define QSPI_WLEN_MAX_BITS		128

#define QSPI_WLEN_MAX_BYTES		16
@@ -106,10 +99,6 @@ struct ti_qspi { 
#define BUSY				0x01

#define WC				0x02



/* INTERRUPT REGISTER */

#define QSPI_WC_INT_EN				(1 << 1)

#define QSPI_WC_INT_DISABLE			(1 << 1)



/* Device Control */

#define QSPI_DD(m, n)			(m << (3 + n * 8))

#define QSPI_CKPHA(n)			(1 << (2 + n * 8))
@@ -217,6 +206,24 @@ static inline u32 qspi_is_busy(struct ti_qspi *qspi) 
	return stat & BUSY;

}



static inline int ti_qspi_poll_wc(struct ti_qspi *qspi)

{

	u32 stat;

	unsigned long timeout = jiffies + QSPI_COMPLETION_TIMEOUT;



	do {

		stat = ti_qspi_read(qspi, QSPI_SPI_STATUS_REG);

		if (stat & WC)

			return 0;

		cpu_relax();

	} while (time_after(timeout, jiffies));



	stat = ti_qspi_read(qspi, QSPI_SPI_STATUS_REG);

	if (stat & WC)

		return 0;

	return  -ETIMEDOUT;

}



static int qspi_write_msg(struct ti_qspi *qspi, struct spi_transfer *t)

{

	int wlen, count, xfer_len;
@@ -275,8 +282,7 @@ static int qspi_write_msg(struct ti_qspi *qspi, struct spi_transfer *t) 
		}



		ti_qspi_write(qspi, cmd, QSPI_SPI_CMD_REG);

		if (!wait_for_completion_timeout(&qspi->transfer_complete,

						 QSPI_COMPLETION_TIMEOUT)) {

		if (ti_qspi_poll_wc(qspi)) {

			dev_err(qspi->dev, "write timed out\n");

			return -ETIMEDOUT;

		}
@@ -315,8 +321,7 @@ static int qspi_read_msg(struct ti_qspi *qspi, struct spi_transfer *t) 
			return -EBUSY;



		ti_qspi_write(qspi, cmd, QSPI_SPI_CMD_REG);

		if (!wait_for_completion_timeout(&qspi->transfer_complete,

						 QSPI_COMPLETION_TIMEOUT)) {

		if (ti_qspi_poll_wc(qspi)) {

			dev_err(qspi->dev, "read timed out\n");

			return -ETIMEDOUT;

		}
@@ -388,9 +393,7 @@ static int ti_qspi_start_transfer_one(struct spi_master *master, 
	qspi->cmd = 0;

	qspi->cmd |= QSPI_EN_CS(spi->chip_select);

	qspi->cmd |= QSPI_FLEN(frame_length);

	qspi->cmd |= QSPI_WC_CMD_INT_EN;



	ti_qspi_write(qspi, QSPI_WC_INT_EN, QSPI_INTR_ENABLE_SET_REG);

	ti_qspi_write(qspi, qspi->dc, QSPI_SPI_DC_REG);



	mutex_lock(&qspi->list_lock);
@@ -418,31 +421,6 @@ static int ti_qspi_start_transfer_one(struct spi_master *master, 
	return status;

}



static irqreturn_t ti_qspi_isr(int irq, void *dev_id)

{

	struct ti_qspi *qspi = dev_id;

	u16 int_stat;

	u32 stat;



	irqreturn_t ret = IRQ_HANDLED;



	int_stat = ti_qspi_read(qspi, QSPI_INTR_STATUS_ENABLED_CLEAR);

	stat = ti_qspi_read(qspi, QSPI_SPI_STATUS_REG);



	if (!int_stat) {

		dev_dbg(qspi->dev, "No IRQ triggered\n");

		ret = IRQ_NONE;

		goto out;

	}



	ti_qspi_write(qspi, QSPI_WC_INT_DISABLE,

				QSPI_INTR_STATUS_ENABLED_CLEAR);

	if (stat & WC)

		complete(&qspi->transfer_complete);

out:

	return ret;

}



static int ti_qspi_runtime_resume(struct device *dev)

{

	struct ti_qspi      *qspi;
@@ -551,22 +529,12 @@ static int ti_qspi_probe(struct platform_device *pdev) 
		}

	}



	ret = devm_request_irq(&pdev->dev, irq, ti_qspi_isr, 0,

			dev_name(&pdev->dev), qspi);

	if (ret < 0) {

		dev_err(&pdev->dev, "Failed to register ISR for IRQ %d\n",

				irq);

		goto free_master;

	}



	qspi->fclk = devm_clk_get(&pdev->dev, "fck");

	if (IS_ERR(qspi->fclk)) {

		ret = PTR_ERR(qspi->fclk);

		dev_err(&pdev->dev, "could not get clk: %d\n", ret);

	}



	init_completion(&qspi->transfer_complete);



	pm_runtime_use_autosuspend(&pdev->dev);

	pm_runtime_set_autosuspend_delay(&pdev->dev, QSPI_AUTOSUSPEND_TIMEOUT);

	pm_runtime_enable(&pdev->dev);
@@ -596,8 +564,6 @@ static int ti_qspi_remove(struct platform_device *pdev) 
		return ret;

	}



	ti_qspi_write(qspi, QSPI_WC_INT_DISABLE, QSPI_INTR_ENABLE_CLEAR_REG);



	pm_runtime_put(qspi->dev);

	pm_runtime_disable(&pdev->dev);