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From:   Eddie James <eajames@linux.ibm.com>
To:     linux-spi@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
        joel@jms.id.au, broonie@kernel.org, bradleyb@fuzziesquirrel.com,
        robh+dt@kernel.org, arnd@arndb.de, eajames@linux.ibm.com
Subject: [PATCH v2 2/6] spi: fsi: Fix clock running too fast
Date:   Wed,  9 Sep 2020 17:28:53 -0500
Message-Id: <20200909222857.28653-3-eajames@linux.ibm.com>
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From: Brad Bishop <bradleyb@fuzziesquirrel.com>

Use a clock divider tuned to a 200MHz FSI bus frequency (the maximum). 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. With FSI
frequencies slower than 200MHz, the SPI clock will simply run slower, but
safely.

Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
Signed-off-by: Eddie James <eajames@linux.ibm.com>
Signed-off-by: Joel Stanley <joel@jms.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