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drm/amd/display: Possible divide by zero in set_speed() 

If "speed" is zero then we use it as a divisor to find "prescale".  It's
better to move the check for zero to the very start of the function.

Fixes: 9eeec26a13 ("drm/amd/display: Refine i2c frequency calculating sequence")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
Dan Carpenter 2020-01-31 07:57:39 +03:00 committed by Alex Deucher
parent 95f247e73f
commit 9543a9c3e2
1 changed files with 12 additions and 11 deletions
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23
drivers/gpu/drm/amd/display/dc/dce/dce_i2c_hw.c
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@ -267,6 +267,9 @@ static void set_speed(
uint32_t xtal_ref_div = 0;
uint32_t prescale = 0;
if (speed == 0)
return;
REG_GET(MICROSECOND_TIME_BASE_DIV, XTAL_REF_DIV, &xtal_ref_div);
if (xtal_ref_div == 0)
@ -274,17 +277,15 @@ static void set_speed(
prescale = ((dce_i2c_hw->reference_frequency * 2) / xtal_ref_div) / speed;
if (speed) {
if (dce_i2c_hw->masks->DC_I2C_DDC1_START_STOP_TIMING_CNTL)
REG_UPDATE_N(SPEED, 3,
FN(DC_I2C_DDC1_SPEED, DC_I2C_DDC1_PRESCALE), prescale,
FN(DC_I2C_DDC1_SPEED, DC_I2C_DDC1_THRESHOLD), 2,
FN(DC_I2C_DDC1_SPEED, DC_I2C_DDC1_START_STOP_TIMING_CNTL), speed > 50 ? 2:1);
else
REG_UPDATE_N(SPEED, 2,
FN(DC_I2C_DDC1_SPEED, DC_I2C_DDC1_PRESCALE), prescale,
FN(DC_I2C_DDC1_SPEED, DC_I2C_DDC1_THRESHOLD), 2);
}
if (dce_i2c_hw->masks->DC_I2C_DDC1_START_STOP_TIMING_CNTL)
REG_UPDATE_N(SPEED, 3,
FN(DC_I2C_DDC1_SPEED, DC_I2C_DDC1_PRESCALE), prescale,
FN(DC_I2C_DDC1_SPEED, DC_I2C_DDC1_THRESHOLD), 2,
FN(DC_I2C_DDC1_SPEED, DC_I2C_DDC1_START_STOP_TIMING_CNTL), speed > 50 ? 2:1);
else
REG_UPDATE_N(SPEED, 2,
FN(DC_I2C_DDC1_SPEED, DC_I2C_DDC1_PRESCALE), prescale,
FN(DC_I2C_DDC1_SPEED, DC_I2C_DDC1_THRESHOLD), 2);
}
static bool setup_engine(