Re: [PATCH] drm/amd/display: Possible divide by zero in set_speed()

2020-03-12 Thread Alex Deucher
Applied.  Thanks!

Alex

On Thu, Jan 30, 2020 at 11:58 PM Dan Carpenter  wrote:
>
> 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: 9eeec26a1339 ("drm/amd/display: Refine i2c frequency calculating 
> sequence")
> Signed-off-by: Dan Carpenter 
> ---
>  drivers/gpu/drm/amd/display/dc/dce/dce_i2c_hw.c | 23 ---
>  1 file changed, 12 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/dce/dce_i2c_hw.c 
> b/drivers/gpu/drm/amd/display/dc/dce/dce_i2c_hw.c
> index 066188ba7949..24adec407972 100644
> --- a/drivers/gpu/drm/amd/display/dc/dce/dce_i2c_hw.c
> +++ b/drivers/gpu/drm/amd/display/dc/dce/dce_i2c_hw.c
> @@ -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, _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(
> --
> 2.11.0
>
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[PATCH] drm/amd/display: Possible divide by zero in set_speed()

2020-01-31 Thread Dan Carpenter
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: 9eeec26a1339 ("drm/amd/display: Refine i2c frequency calculating 
sequence")
Signed-off-by: Dan Carpenter 
---
 drivers/gpu/drm/amd/display/dc/dce/dce_i2c_hw.c | 23 ---
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dce/dce_i2c_hw.c 
b/drivers/gpu/drm/amd/display/dc/dce/dce_i2c_hw.c
index 066188ba7949..24adec407972 100644
--- a/drivers/gpu/drm/amd/display/dc/dce/dce_i2c_hw.c
+++ b/drivers/gpu/drm/amd/display/dc/dce/dce_i2c_hw.c
@@ -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, _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(
-- 
2.11.0

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