From b8a204fb1a97b39a7fcaefbf2c6c4d01aa4f3c57 Mon Sep 17 00:00:00 2001 From: Nicholas Kazlauskas Date: Thu, 14 Dec 2023 16:46:35 -0500 Subject: [PATCH] drm/amd/display: Verify disallow bits were cleared for idle [Why] A hang was observed where a read-modify-write access occurred due to the register for idle state being shared between DMCUB and driver. dmcub read - idle allow / no commit driver read - idle allow / no commit driver write - idle disallow / no commit dmcub write - idle allow / commit Resulting in DMCUB re-entering IPS after a disable and keeping the allow high. [How] Long term we need to split commit/allow into two registers or use shared DRAM state, but short term we can reduce the repro rate by ensuring that the disallow went through by bounding the expected worst case scenario. Tested-by: Daniel Wheeler Reviewed-by: Hansen Dsouza Reviewed-by: Ovidiu Bunea Acked-by: Rodrigo Siqueira Signed-off-by: Nicholas Kazlauskas Signed-off-by: Alex Deucher --- drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c b/drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c index dadeaa9c92dd5..a65c485b0b49a 100644 --- a/drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c +++ b/drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c @@ -1233,8 +1233,16 @@ static void dc_dmub_srv_exit_low_power_state(const struct dc *dc) if (!(allow_state & DMUB_IPS2_ALLOW_MASK)) { // Wait for evaluation time - udelay(dc->debug.ips2_eval_delay_us); - commit_state = dc->hwss.get_idle_state(dc); + for (;;) { + udelay(dc->debug.ips2_eval_delay_us); + commit_state = dc->hwss.get_idle_state(dc); + if (commit_state & DMUB_IPS2_ALLOW_MASK) + break; + + /* allow was still set, retry eval delay */ + dc->hwss.set_idle_state(dc, false); + } + if (!(commit_state & DMUB_IPS2_COMMIT_MASK)) { // Tell PMFW to exit low power state dc->clk_mgr->funcs->exit_low_power_state(dc->clk_mgr); -- 2.30.2