linux-kernel - [PATCH 2/7] spi: fsi: Fix clock running too fast

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Message-Id: <20200820170228.42053-3-eajames@linux.ibm.com>
Date:   Thu, 20 Aug 2020 12:02:23 -0500
From:   Eddie James <eajames@...ux.ibm.com>
To:     linux-spi@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        eajames@...ux.ibm.com, joel@....id.au, bradleyb@...ziesquirrel.com,
        broonie@...nel.org, robh+dt@...nel.org, arnd@...db.de
Subject: [PATCH 2/7] spi: fsi: Fix clock running too fast

From: Brad Bishop <bradleyb@...ziesquirrel.com>

Use a clock divider tuned to a 200MHz FSI clock.  Use of the previous
divider at 200MHz results in corrupt data from endpoint devices. Ideally
the clock divider would be calculated from the FSI clock, but that
would require some significant work on the FSI driver.

Signed-off-by: Brad Bishop <bradleyb@...ziesquirrel.com>
Signed-off-by: Eddie James <eajames@...ux.ibm.com>
Signed-off-by: Joel Stanley <joel@....id.au>
---
 drivers/spi/spi-fsi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/spi/spi-fsi.c b/drivers/spi/spi-fsi.c
index 8f64af0140e0..559d0ff981f3 100644
--- a/drivers/spi/spi-fsi.c
+++ b/drivers/spi/spi-fsi.c
@@ -350,7 +350,7 @@ static int fsi_spi_transfer_init(struct fsi_spi *ctx)
 	u64 status = 0ULL;
 	u64 wanted_clock_cfg = SPI_FSI_CLOCK_CFG_ECC_DISABLE |
 		SPI_FSI_CLOCK_CFG_SCK_NO_DEL |
-		FIELD_PREP(SPI_FSI_CLOCK_CFG_SCK_DIV, 4);
+		FIELD_PREP(SPI_FSI_CLOCK_CFG_SCK_DIV, 19);
 
 	end = jiffies + msecs_to_jiffies(SPI_FSI_INIT_TIMEOUT_MS);
 	do {
-- 
2.26.2