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Message-ID: <1444731665-11359-1-git-send-email-vigneshr@ti.com>
Date: Tue, 13 Oct 2015 15:51:05 +0530
From: Vignesh R <vigneshr@...com>
To: Mark Brown <broonie@...nel.org>
CC: <linux-spi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<linux-omap@...r.kernel.org>, Vignesh R <vigneshr@...com>
Subject: [PATCH] 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: Vignesh R <vigneshr@...com>
---
Tested on DRA74 Rev G EVM.
drivers/spi/spi-ti-qspi.c | 74 +++++++++++++----------------------------------
1 file changed, 20 insertions(+), 54 deletions(-)
diff --git a/drivers/spi/spi-ti-qspi.c b/drivers/spi/spi-ti-qspi.c
index 81b84858cfee..69c1a95b0615 100644
--- a/drivers/spi/spi-ti-qspi.c
+++ b/drivers/spi/spi-ti-qspi.c
@@ -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);
@@ -417,31 +420,6 @@ 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;
@@ -550,22 +528,12 @@ 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);
@@ -595,8 +563,6 @@ 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);
--
2.6.1
--
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