On 2015-05-20 18:14, Daniel Stone wrote:
Hi,
On 20 May 2015 at 17:04, Tobias Jakobi <tjakobi@xxxxxxxxxxxxxxxxxxxxx>
wrote:
Hmm,
I wonder if that really 'fixes' anything, because now we get a WARN_ON
which
is immediately followed by a div-by-zero. Furthermore we then still
use the
result of that operation as input for a hw register (bad idea?)
I thought of something like this. Change fimd_calc_clkdiv() to return
a
signed value (this shouldn't be a problem, since the returned number
range
is small anywary). Let fimd_calc_clkdiv() return -1 when it encounters
the
'ideal_clk == 0' case. Move computation of clkdiv in fimd_commit() to
the
top of the function (right after the {h,v}total checks). If 'clkdiv ==
-1'
case is encountered, then do WARN_ON and return immediately from
fimd_commit().
Should I prepare a patch for this, or does someone see an issue with
this
approach?
Commit should never fail; as I said earlier, the right fix is to
reject these modes during checking, by making sure that any mode which
passes mode_fixup() and/or mode_valid() never trips this condition.
But then in this case it wouldn't help to call drm_mode_vrefresh()
during fixup, since it still returns zero, so we're in the same
situation as before.
I even wonder if fixup is doing anything at all. See my previous log in:
http://www.spinics.net/lists/linux-samsung-soc/msg44683.html
This is with the old code in fixup that should set vrefresh to 60.
And we see that it's actually called:
[ 135.978878] [drm:fimd_mode_fixup] vrefresh 0
But then a small while later:
[ 135.979048] [drm:fimd_calc_clkdiv] vrefresh 0
So apparantly nothing was fixed up here anyway?!
With best wishes,
Tobias
Cheers,
Daniel
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