linux-kernel - [PATCH v4 3/6] spi: cadence-qspi: add early busywait to cqspi_wait_for

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Message-Id: <20240423-cdns-qspi-mbly-v4-3-3d2a7b535ad0@bootlin.com>
Date: Tue, 23 Apr 2024 12:01:42 +0200
From: Théo Lebrun <theo.lebrun@...tlin.com>
To: Mark Brown <broonie@...nel.org>, Rob Herring <robh+dt@...nel.org>, 
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, 
 Conor Dooley <conor+dt@...nel.org>, Vaishnav Achath <vaishnav.a@...com>, 
 Thomas Bogendoerfer <tsbogend@...ha.franken.de>, 
 Rob Herring <robh@...nel.org>
Cc: linux-spi@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-mips@...r.kernel.org, 
 Vladimir Kondratiev <vladimir.kondratiev@...ileye.com>, 
 Gregory CLEMENT <gregory.clement@...tlin.com>, 
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 Tawfik Bayouk <tawfik.bayouk@...ileye.com>, 
 Théo Lebrun <theo.lebrun@...tlin.com>
Subject: [PATCH v4 3/6] spi: cadence-qspi: add early busywait to
 cqspi_wait_for_bit()

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.

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

Signed-off-by: Théo Lebrun <theo.lebrun@...tlin.com>
---
 drivers/spi/spi-cadence-quadspi.c | 31 +++++++++++++++++++++++--------
 1 file changed, 23 insertions(+), 8 deletions(-)

diff --git a/drivers/spi/spi-cadence-quadspi.c b/drivers/spi/spi-cadence-quadspi.c
index a82e23526a6f..87c88ee708e4 100644
--- a/drivers/spi/spi-cadence-quadspi.c
+++ b/drivers/spi/spi-cadence-quadspi.c
@@ -120,6 +120,7 @@ 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
@@ -298,13 +299,27 @@ 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) {
+		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)
@@ -434,8 +449,8 @@ 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");
@@ -790,8 +805,8 @@ 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;
@@ -1091,8 +1106,8 @@ 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