spi: fsi: Fix clock running too fast

[ Upstream commit 0b546bbe9474ff23e6843916ad6d567f703b2396 ]

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>
Link: https://lore.kernel.org/r/20200909222857.28653-3-eajames@linux.ibm.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/spi/spi-fsi.c b/drivers/spi/spi-fsi.c
index ef5e0826a53c3f108949477e51d25be110e32a7b..a702e9d7d68c08108282f3998aa83540b08172d0 100644 (file)
--- a/drivers/spi/spi-fsi.c
+++ b/drivers/spi/spi-fsi.c
@@ -403,7 +403,7 @@ 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 {