linux-kernel - [PATCH v2 4/4] spi: amd: Don't wait for a write-only transfer to finish

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Date:   Fri, 10 Sep 2021 12:15:29 +0100
From:   Lucas Tanure <tanureal@...nsource.cirrus.com>
To:     Mark Brown <broonie@...nel.org>,
        Sanjay R Mehta <sanju.mehta@....com>,
        Nehal Bakulchandra Shah <Nehal-Bakulchandra.shah@....com>
CC:     <linux-kernel@...r.kernel.org>, <linux-spi@...r.kernel.org>,
        <patches@...nsource.cirrus.com>,
        Lucas Tanure <tanureal@...nsource.cirrus.com>
Subject: [PATCH v2 4/4] spi: amd: Don't wait for a write-only transfer to finish

Return from a write-only transfer without waiting for
it to finish
But wait before a new transfer as the previous may
still happening and also wait before reading the data
from the FIFO

Signed-off-by: Lucas Tanure <tanureal@...nsource.cirrus.com>
---

Changes in v2:
Add wait before read data
New explanation

 drivers/spi/spi-amd.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi-amd.c b/drivers/spi/spi-amd.c
index 97838b57871c..4b3ac7aceaf6 100644
--- a/drivers/spi/spi-amd.c
+++ b/drivers/spi/spi-amd.c
@@ -115,11 +115,18 @@ static int amd_spi_busy_wait(struct amd_spi *amd_spi)
 	return 0;
 }
 
-static void amd_spi_execute_opcode(struct amd_spi *amd_spi)
+static int amd_spi_execute_opcode(struct amd_spi *amd_spi)
 {
+	int ret;
+
+	ret = amd_spi_busy_wait(amd_spi);
+	if (ret)
+		return ret;
+
 	/* Set ExecuteOpCode bit in the CTRL0 register */
 	amd_spi_setclear_reg32(amd_spi, AMD_SPI_CTRL0_REG, AMD_SPI_EXEC_CMD, AMD_SPI_EXEC_CMD);
-	amd_spi_busy_wait(amd_spi);
+
+	return 0;
 }
 
 static int amd_spi_master_setup(struct spi_device *spi)
@@ -178,6 +185,7 @@ static inline int amd_spi_fifo_xfer(struct amd_spi *amd_spi,
 			amd_spi_clear_fifo_ptr(amd_spi);
 			/* Execute command */
 			amd_spi_execute_opcode(amd_spi);
+			amd_spi_busy_wait(amd_spi);
 			/* Read data from FIFO to receive buffer  */
 			for (i = 0; i < rx_len; i++)
 				buf[i] = amd_spi_readreg8(amd_spi, AMD_SPI_FIFO_BASE + tx_len + i);
-- 
2.33.0