drm/vc4: Skip input lines when doing a large downscale#7387
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The TPZ filter wants ideally 3 lines of image to give good quality downscaling. More than that leads to excessive SDRAM bandwidth for no gain. If the downsample factor allows for it, reduce the programmed image height and increase the pitch to compensate. This currently does not handle T-format images where we need to configure it slightly differently. Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
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Confirmed as working. |
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I understand the logic behind it. Provided the downsample value gets set in all code paths (it wasn't trivially obvious that it was), and the results looks OK, I approve. |
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The existing behaviour is, in the worst case, to cease displaying video at all so this is a great improvement |
popcornmix
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kernel: edatec Open Source HMI for 10 inches panel driver See: raspberrypi/linux#7362 kernel: configs: Enable MT7921 and MT7922 support See: raspberrypi/linux#7416 kernel: drm/vc4: Skip input lines when doing a large downscale See: raspberrypi/linux#7387 kernel: Revert "random: do not use jump labels before they are initialized" See: raspberrypi/linux#7425
popcornmix
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Jun 10, 2026
kernel: edatec Open Source HMI for 10 inches panel driver See: raspberrypi/linux#7362 kernel: configs: Enable MT7921 and MT7922 support See: raspberrypi/linux#7416 kernel: drm/vc4: Skip input lines when doing a large downscale See: raspberrypi/linux#7387 kernel: Revert "random: do not use jump labels before they are initialized" See: raspberrypi/linux#7425
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The TPZ filter wants ideally 3 lines of image to give good quality downscaling. More than that leads to excessive SDRAM bandwidth for no gain.
If the downsample factor allows for it, reduce the programmed image height and increase the pitch to compensate.
This currently does not handle T-format images where we need to configure it slightly differently.
@jc-kynesim : This should solve your 10bittest massive downscale issue.