Re: drm/mgag200: don't use uninitialized variables in mga_g200se_set_plls()

[Mathieu Larouche <mathieu.larouche@matrox.com>]

On 19/10/2015 6:29 AM, Jan Beulich wrote:
> I can only guess that instead of testm/testn (which are either
> uninitialized or have pre-determined values at the end of the preceding
> loops) n and m were meant to be used by commit e829d7ef9f
> ("drm/mgag200: Add support for a new rev of G200e"). In any event the
> compiler is right in warning that testm/testn are possibly uninitalized
> at this point, i.e. some change is needed no matter what.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> Cc: Mathieu Larouche <mathieu.larouche@matrox.com>
> ---
>   drivers/gpu/drm/mgag200/mgag200_mode.c |    2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- 4.3-rc6/drivers/gpu/drm/mgag200/mgag200_mode.c
> +++ 4.3-rc6-mgag200-uninit/drivers/gpu/drm/mgag200/mgag200_mode.c
> @@ -194,7 +194,7 @@ static int mga_g200se_set_plls(struct mg
>   			}
>   		}
>   
> -		fvv = pllreffreq * testn / testm;
> +		fvv = pllreffreq * n / m;
>   		fvv = (fvv - 800000) / 50000;
>   
>   		if (fvv > 15)
>
>
>
>
If you are using n/m instead of testn/testm, you need to
add 1 to the variables to keep consistency. However, you
have the same issue where m/n could be used without being
initialized. So, I propose to keep testm, testn & testp
and initialized them with the default value.

Signed-off-by: Mathieu Larouche <mathieu.larouche@matrox.com>
---
  drivers/gpu/drm/mgag200/mgag200_mode.c | 6 ++++++
  1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c b/drivers/gpu/drm/mgag200/mgag200_mode.c
index c99d3fe..055799c 100644
--- a/drivers/gpu/drm/mgag200/mgag200_mode.c
+++ b/drivers/gpu/drm/mgag200/mgag200_mode.c
@@ -123,6 +123,9 @@ static int mga_g200se_set_plls(struct mga_device *mdev, long clock)
  		vcomax = 320000;
  		vcomin = 160000;
  		pllreffreq = 25000;
+		testm = 1;
+		testn = 17;
+		testp = 8;
  
  		delta = 0xffffffff;
  		permitteddelta = clock * 5 / 1000;
@@ -157,6 +160,9 @@ static int mga_g200se_set_plls(struct mga_device *mdev, long clock)
  		vcomax        = 1600000;
  		vcomin        = 800000;
  		pllreffreq    = 25000;
+		testm         = 1;
+		testn         = 50;
+		testp         = 16;
  
  		if (clock < 25000)
  			clock = 25000;

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