Re: [PATCH 03/10] drm/i915: Write out crc frame counts in hex

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Dec 16, 2015 at 11:23:54AM +0100, Daniel Vetter wrote:
> On Mon, Dec 14, 2015 at 06:23:42PM +0200, ville.syrjala@linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > The crc code assumes that the printed frame counter value takes
> > exactly 8 characters. The counter is a 32bit value, so to fit
> > it into 8 characters we need to print it in hex, in decimal it
> > would take 10 characters.
> > 
> > This obviously needs a corresponding change in intel-gpu-tools.
> > 
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> ugh, and we hardcode the same %8u on the igt side. What about instead
> changing igt to just parse for an %u, push that, then change the kernel to
> dump a %u without length? With a few months in between.
> 
> At least some backwards compat must be there, otherwise bisecting will be
> slightly painful.

So the other idea I had was to limit the counter to 24 bits always. That
would avoid having to change the printf format string at all, and it
would gives us a consistent wraparound behaviour (since gen3/4 frame
counter is only 24 bits).


> -Daniel
> 
> > ---
> >  drivers/gpu/drm/i915/i915_debugfs.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> > index 24318b79bcfc..96d6e5de0811 100644
> > --- a/drivers/gpu/drm/i915/i915_debugfs.c
> > +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> > @@ -3518,7 +3518,7 @@ i915_pipe_crc_read(struct file *filep, char __user *user_buf, size_t count,
> >  		pipe_crc->tail = (pipe_crc->tail + 1) & (INTEL_PIPE_CRC_ENTRIES_NR - 1);
> >  
> >  		bytes_read += snprintf(buf, PIPE_CRC_BUFFER_LEN,
> > -				       "%8u %8x %8x %8x %8x %8x\n",
> > +				       "%8x %8x %8x %8x %8x %8x\n",
> >  				       entry->frame, entry->crc[0],
> >  				       entry->crc[1], entry->crc[2],
> >  				       entry->crc[3], entry->crc[4]);
> > -- 
> > 2.4.10
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

-- 
Ville Syrjälä
Intel OTC
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