spi: spi-fsl-lpspi: Fix scldiv calculation

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The effective SPI clock frequency should never exceed speed_hz
otherwise this might result in undefined behavior of the SPI device.

Currently the scldiv calculation could violate this constraint.
For the example parameters perclk_rate = 24 MHz and speed_hz = 7 MHz,
the function fsl_lpspi_set_bitrate will determine perscale = 0 and
scldiv = 1, which is a effective SPI clock of 8 MHz.

So fix this by rounding up the quotient of perclk_rate and speed_hz.
While this never change within the loop, we can pull this out.

Fixes: 5314987de5 ("spi: imx: add lpspi bus driver")
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Link: https://patch.msgid.link/20240804113611.83613-1-wahrenst@gmx.net
Signed-off-by: Mark Brown <broonie@kernel.org>

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Stefan Wahren 2024-08-04 13:36:11 +02:00 • committed by Mark Brown

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commit 730bbfaf7d

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drivers/spi/spi-fsl-lpspi.c

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