[PATCH v2 08/11] spi: cadence-qspi: add early busywait to cqspi_wait_for_bit()

[Théo Lebrun]

If the CQSPI_BUSYWAIT_EARLY quirk flag is on, call
readl_relaxed_poll_timeout() with no sleep at the start of
cqspi_wait_for_bit(). If its short timeout expires, a sleeping
readl_relaxed_poll_timeout() call takes the relay.

Behavior is hidden behind a quirk flag to keep the previous behavior the
same on all platforms.

The reason is to avoid hrtimer interrupts on the system. All read
operations take less than 100µs.

Signed-off-by: Théo Lebrun <theo.lebrun@xxxxxxxxxxx>
---
 drivers/spi/spi-cadence-quadspi.c | 34 +++++++++++++++++++++++++---------
 1 file changed, 25 insertions(+), 9 deletions(-)

diff --git a/drivers/spi/spi-cadence-quadspi.c b/drivers/spi/spi-cadence-quadspi.c
index ebb8c35f50fd..230aad490e03 100644
--- a/drivers/spi/spi-cadence-quadspi.c
+++ b/drivers/spi/spi-cadence-quadspi.c
@@ -44,6 +44,7 @@ static_assert(CQSPI_MAX_CHIPSELECT <= SPI_CS_CNT_MAX);
 #define CQSPI_NEEDS_APB_AHB_HAZARD_WAR	BIT(5)
 #define CQSPI_DETECT_FIFO_DEPTH		BIT(6)
 #define CQSPI_RD_NO_IRQ			BIT(7)
+#define CQSPI_BUSYWAIT_EARLY		BIT(8)
 
 /* Capabilities */
 #define CQSPI_SUPPORTS_OCTAL		BIT(0)
@@ -110,7 +111,7 @@ struct cqspi_st {
 
 struct cqspi_driver_platdata {
 	u32 hwcaps_mask;
-	u8 quirks;
+	u16 quirks;
 	int (*indirect_read_dma)(struct cqspi_flash_pdata *f_pdata,
 				 u_char *rxbuf, loff_t from_addr, size_t n_rx);
 	u32 (*get_dma_status)(struct cqspi_st *cqspi);
@@ -121,6 +122,7 @@ struct cqspi_driver_platdata {
 /* Operation timeout value */
 #define CQSPI_TIMEOUT_MS			500
 #define CQSPI_READ_TIMEOUT_MS			10
+#define CQSPI_BUSYWAIT_TIMEOUT_US		500
 
 /* Runtime_pm autosuspend delay */
 #define CQSPI_AUTOSUSPEND_TIMEOUT		2000
@@ -299,13 +301,27 @@ struct cqspi_driver_platdata {
 
 #define CQSPI_REG_VERSAL_DMA_VAL		0x602
 
-static int cqspi_wait_for_bit(void __iomem *reg, const u32 mask, bool clr)
+static int cqspi_wait_for_bit(const struct cqspi_driver_platdata *ddata,
+			      void __iomem *reg, const u32 mask, bool clr,
+			      bool busywait)
 {
+	u64 timeout_us = CQSPI_TIMEOUT_MS * USEC_PER_MSEC;
 	u32 val;
 
+	if (busywait && ddata && ddata->quirks & CQSPI_BUSYWAIT_EARLY) {
+		int ret = readl_relaxed_poll_timeout(reg, val,
+						     (((clr ? ~val : val) & mask) == mask),
+						     0, CQSPI_BUSYWAIT_TIMEOUT_US);
+
+		if (ret != -ETIMEDOUT)
+			return ret;
+
+		timeout_us -= CQSPI_BUSYWAIT_TIMEOUT_US;
+	}
+
 	return readl_relaxed_poll_timeout(reg, val,
 					  (((clr ? ~val : val) & mask) == mask),
-					  10, CQSPI_TIMEOUT_MS * 1000);
+					  10, timeout_us);
 }
 
 static bool cqspi_is_idle(struct cqspi_st *cqspi)
@@ -435,8 +451,8 @@ static int cqspi_exec_flash_cmd(struct cqspi_st *cqspi, unsigned int reg)
 	writel(reg, reg_base + CQSPI_REG_CMDCTRL);
 
 	/* Polling for completion. */
-	ret = cqspi_wait_for_bit(reg_base + CQSPI_REG_CMDCTRL,
-				 CQSPI_REG_CMDCTRL_INPROGRESS_MASK, 1);
+	ret = cqspi_wait_for_bit(cqspi->ddata, reg_base + CQSPI_REG_CMDCTRL,
+				 CQSPI_REG_CMDCTRL_INPROGRESS_MASK, 1, true);
 	if (ret) {
 		dev_err(&cqspi->pdev->dev,
 			"Flash command execution timed out.\n");
@@ -791,8 +807,8 @@ static int cqspi_indirect_read_execute(struct cqspi_flash_pdata *f_pdata,
 	}
 
 	/* Check indirect done status */
-	ret = cqspi_wait_for_bit(reg_base + CQSPI_REG_INDIRECTRD,
-				 CQSPI_REG_INDIRECTRD_DONE_MASK, 0);
+	ret = cqspi_wait_for_bit(cqspi->ddata, reg_base + CQSPI_REG_INDIRECTRD,
+				 CQSPI_REG_INDIRECTRD_DONE_MASK, 0, true);
 	if (ret) {
 		dev_err(dev, "Indirect read completion error (%i)\n", ret);
 		goto failrd;
@@ -1092,8 +1108,8 @@ static int cqspi_indirect_write_execute(struct cqspi_flash_pdata *f_pdata,
 	}
 
 	/* Check indirect done status */
-	ret = cqspi_wait_for_bit(reg_base + CQSPI_REG_INDIRECTWR,
-				 CQSPI_REG_INDIRECTWR_DONE_MASK, 0);
+	ret = cqspi_wait_for_bit(cqspi->ddata, reg_base + CQSPI_REG_INDIRECTWR,
+				 CQSPI_REG_INDIRECTWR_DONE_MASK, 0, false);
 	if (ret) {
 		dev_err(dev, "Indirect write completion error (%i)\n", ret);
 		goto failwr;

-- 
2.44.0