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spi: sh-msiof: Fix bit field overflow writes to TSCR/RSCR 

The change fixes a bit field overflow which allows to write to higher
bits while calculating SPI transfer clock and setting BRPS and BRDV
bit fields, the problem is reproduced if 'parent_rate' to 'spi_hz'
ratio is greater than 1024, for instance

  p->min_div      = 2,
  MSO rate        = 33333333,
  SPI device rate = 10000

results in

  k          = 5, i.e. BRDV = 0b100 or 1/32 prescaler output,
  BRPS       = 105,
  TSCR value = 0x6804, thus MSSEL and MSIMM bit fields are non-zero.

Fixes: 65d5665bb2 ("spi: sh-msiof: Update calculation of frequency dividing")
Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
zero-colors
Vladimir Zapolskiy 2018-04-13 15:44:16 +03:00 committed by Mark Brown
parent af82800cd2
commit 10b4640833
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GPG Key ID: 24D68B725D5487D0
1 changed files with 1 additions and 0 deletions
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drivers/spi/spi-sh-msiof.c
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@ -283,6 +283,7 @@ static void sh_msiof_spi_set_clk_regs(struct sh_msiof_spi_priv *p,
}
k = min_t(int, k, ARRAY_SIZE(sh_msiof_spi_div_table) - 1);
brps = min_t(int, brps, 32);
scr = sh_msiof_spi_div_table[k].brdv | SCR_BRPS(brps);
sh_msiof_write(p, TSCR, scr);