linux-kernel - [PATCH 1/2] spi: cadence-quadspi: Disable Auto-HW polling

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Date:   Tue, 13 Jul 2021 12:57:41 +0000
From:   Apurva Nandan <a-nandan@...com>
To:     Mark Brown <broonie@...nel.org>, <linux-spi@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Apurva Nandan <a-nandan@...com>, Pratyush Yadav <p.yadav@...com>,
        Vignesh Raghavendra <vigneshr@...com>
Subject: [PATCH 1/2] spi: cadence-quadspi: Disable Auto-HW polling

cadence-quadspi has a builtin Auto-HW polling funtionality using which
it keep tracks of completion of write operations. When Auto-HW polling
is enabled, it automatically initiates status register read operation,
until the flash clears its busy bit.

cadence-quadspi controller doesn't allow an address phase when
auto-polling the busy bit on the status register. Unlike SPI NOR
flashes, SPI NAND flashes do require the address of status register
when polling the busy bit using the read register operation. As
Auto-HW polling is enabled by default, cadence-quadspi returns a
timeout for every write operation after an indefinite amount of
polling on SPI NAND flashes.

Disable Auto-HW polling completely as the spi-nor core, spinand core,
etc. take care of polling the busy bit on their own.

Signed-off-by: Apurva Nandan <a-nandan@...com>
---
 drivers/spi/spi-cadence-quadspi.c | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/drivers/spi/spi-cadence-quadspi.c b/drivers/spi/spi-cadence-quadspi.c
index 7a00346ff9b9..a2e1f4ce8b3e 100644
--- a/drivers/spi/spi-cadence-quadspi.c
+++ b/drivers/spi/spi-cadence-quadspi.c
@@ -797,19 +797,20 @@ static int cqspi_write_setup(struct cqspi_flash_pdata *f_pdata,
 	reg = cqspi_calc_rdreg(f_pdata);
 	writel(reg, reg_base + CQSPI_REG_RD_INSTR);
 
-	if (f_pdata->dtr) {
-		/*
-		 * Some flashes like the cypress Semper flash expect a 4-byte
-		 * dummy address with the Read SR command in DTR mode, but this
-		 * controller does not support sending address with the Read SR
-		 * command. So, disable write completion polling on the
-		 * controller's side. spi-nor will take care of polling the
-		 * status register.
-		 */
-		reg = readl(reg_base + CQSPI_REG_WR_COMPLETION_CTRL);
-		reg |= CQSPI_REG_WR_DISABLE_AUTO_POLL;
-		writel(reg, reg_base + CQSPI_REG_WR_COMPLETION_CTRL);
-	}
+	/*
+	 * SPI NAND flashes require the address of the status register to be
+	 * passed in the Read SR command. Also, some SPI NOR flashes like the
+	 * cypress Semper flash expect a 4-byte dummy address in the Read SR
+	 * command in DTR mode.
+	 *
+	 * But this controller does not support address phase in the Read SR
+	 * command when doing auto-HW polling. So, disable write completion
+	 * polling on the controller's side. spinand and spi-nor will take
+	 * care of polling the status register.
+	 */
+	reg = readl(reg_base + CQSPI_REG_WR_COMPLETION_CTRL);
+	reg |= CQSPI_REG_WR_DISABLE_AUTO_POLL;
+	writel(reg, reg_base + CQSPI_REG_WR_COMPLETION_CTRL);
 
 	reg = readl(reg_base + CQSPI_REG_SIZE);
 	reg &= ~CQSPI_REG_SIZE_ADDRESS_MASK;
-- 
2.17.1