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spi: sh-msiof: Avoid invalid clock generator parameters 

The conversion from a look-up table to a calculation for clock generator
parameters forgot to take into account that BRDV x 1/1 is valid only if
BRPS is x 1/1 or x 1/2, leading to undefined behavior (e.g. arbitrary
clock rates).

This limitation is documented for the MSIOF module in all supported
SH/R-Mobile and R-Car Gen2/Gen3 ARM SoCs.

Tested on r8a7791/koelsch and r8a7795/salvator-x.

Fixes: 65d5665bb2 ("spi: sh-msiof: Update calculation of frequency dividing")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Geert Uytterhoeven 2016-08-05 10:17:52 +02:00 committed by Mark Brown
parent dec34e8b67
commit c3ccf357c3
1 changed files with 3 additions and 0 deletions
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3
drivers/spi/spi-sh-msiof.c
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@ -262,6 +262,9 @@ static void sh_msiof_spi_set_clk_regs(struct sh_msiof_spi_priv *p,
for (k = 0; k < ARRAY_SIZE(sh_msiof_spi_div_table); k++) {
brps = DIV_ROUND_UP(div, sh_msiof_spi_div_table[k].div);
/* SCR_BRDV_DIV_1 is valid only if BRPS is x 1/1 or x 1/2 */
if (sh_msiof_spi_div_table[k].div == 1 && brps > 2)
continue;
if (brps <= 32) /* max of brdv is 32 */
break;
}