05:48 <TellowKrinkle> Hello! I'm trying to run Dolphin on a Libre Computer Solitude (Amlogic S905D3 / Mali G31), and it looks like tiles of the depth buffer are randomly getting cleared to 0.

05:48 <TellowKrinkle> This seems to always happen after a panfrost_flush call (usually caused by a glFenceSync from Dolphin, but I've also seen it happen with glReadPixels on the depth buffer).

05:48 <TellowKrinkle> Editing mesa to change the depth pre frame mode from MALI_PRE_POST_FRAME_SHADER_MODE_EARLY_ZS_ALWAYS to MALI_PRE_POST_FRAME_SHADER_MODE_ALWAYS seems to fix the issue. What's the difference between the various MALI_PRE_POST_FRAME_SHADER_MODEs?

20:17 <benjaminl> tellowkrinkle: the pre-frame modes control whether the pre-frame shader is run for each tile. NEVER and ALWAYS are no tiles/all tiles respectively. INTERSECT only runs the shader for tiles that contain geometry in a given draw. EARLY_ZS_ALWAYS is like ALWAYS but optimized for depth/stencil. The shader can only write ZS in this mode.

20:22 <benjaminl> ... is G31 actually v7?

20:23 <benjaminl> v6 doesn't support EARLY_ZS_ALWAYS, so if it's being misclassified that might be the problem

23:20 <pac85> benjaminl: Yeah mesa checks if it is on > v6 https://gitlab.freedesktop.org/mesa/mesa/-/blob/main/src/gallium/drivers/panfrost/pan_fb_preload.c?ref_type=heads#L1217

23:21 <pac85> Are there any requirements other than the shader only writing zs?

23:23 <pac85> I see the shader also doing ATEST, is that ok?

23:53 <benjaminl> pac85: it must only write zs, it must write zs for every fragment, the render state zs_update_operation must be set to MALI_PIXEL_KILL_FORCE_LATE (this is required whenever a shader writes zs)

23:54 <benjaminl> I believe ATEST is required if you use ZS_EMIT

23:54 <TellowKrinkle> I also tried adjusting the v7 check to fail, and then it picks _INTERSECT which ends up making the depth look slightly different but just as broken.

23:58 <pac85> benjaminl: I see thanks

23:59 <benjaminl> hmm... any idea if the cleared tiles are all the tiles that are touched by the next draws, or possibly all the tiles that *are not* touched by the next draws?