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spi: pxa2xx: Set minimum transfer speed

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It is possible to request a transfer with a speed lower than supported
by the HW. This causes silent divider calculation underflow in
ssp_get_clk_div() which leads to a frequency higher than requested. Up to
maximum speed of the controller.

Set the minimum supported transfer speed and let the SPI core to
validate no transfers have speed lower than supported.

Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Jarkko Nikula 2019-06-28 17:07:17 +03:00 committed by Mark Brown
parent 775c4c0032
commit 23cdddb21f
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GPG key ID: 24D68B725D5487D0
1 changed files with 10 additions and 0 deletions
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10
drivers/spi/spi-pxa2xx.c
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@ -1704,6 +1704,16 @@ static int pxa2xx_spi_probe(struct platform_device *pdev)
goto out_error_dma_irq_alloc;
controller->max_speed_hz = clk_get_rate(ssp->clk);
/*
* Set minimum speed for all other platforms than Intel Quark which is
* able do under 1 Hz transfers.
*/
if (!pxa25x_ssp_comp(drv_data))
controller->min_speed_hz =
DIV_ROUND_UP(controller->max_speed_hz, 4096);
else if (!is_quark_x1000_ssp(drv_data))
controller->min_speed_hz =
DIV_ROUND_UP(controller->max_speed_hz, 512);
/* Load default SSP configuration */
pxa2xx_spi_write(drv_data, SSCR0, 0);