From d2aa1356834d845ffdac0d8c01b58aa60d1bdc65 Mon Sep 17 00:00:00 2001 From: Aurabindo Pillai Date: Wed, 19 May 2021 16:51:01 -0400 Subject: [PATCH] drm/amd/display: take dc_lock in short pulse handler only [Why] Conditions that end up modifying the global dc state must be locked. However, during mst allocate payload sequence, lock is already taken. With StarTech 1.2 DP hub, we get an HPD RX interrupt for a reason other than to indicate down reply availability right after sending payload allocation. The handler again takes dc lock before calling the dc's HPD RX handler. Due to this contention, the DRM thread which waits for MST down reply never gets a chance to finish its waiting successfully and ends up timing out. Once the lock is released, the hpd rx handler fires and goes ahead to read from the MST HUB, but now its too late and the HUB doesnt lightup all displays since DRM lacks error handling when payload allocation fails. [How] Take lock only if there is a change in link status or if automated test pattern bit is set. The latter fixes the null pointer dereference when running certain DP Link Layer Compliance test. Fixes: c8ea79a8a276 ("drm/amd/display: NULL pointer error during compliance test") Signed-off-by: Aurabindo Pillai Reviewed-by: Nicholas Kazlauskas Signed-off-by: Alex Deucher --- .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 19 +++++++++++++++++-- .../gpu/drm/amd/display/dc/core/dc_link_dp.c | 2 +- .../gpu/drm/amd/display/dc/inc/dc_link_dp.h | 4 ++++ 3 files changed, 22 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c index 515b6d7d91287..a4016fff51cdc 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c @@ -28,6 +28,7 @@ #include "dm_services_types.h" #include "dc.h" +#include "dc_link_dp.h" #include "dc/inc/core_types.h" #include "dal_asic_id.h" #include "dmub/dmub_srv.h" @@ -2739,6 +2740,7 @@ static void handle_hpd_rx_irq(void *param) enum dc_connection_type new_connection_type = dc_connection_none; struct amdgpu_device *adev = drm_to_adev(dev); union hpd_irq_data hpd_irq_data; + bool lock_flag = 0; memset(&hpd_irq_data, 0, sizeof(hpd_irq_data)); @@ -2768,15 +2770,28 @@ static void handle_hpd_rx_irq(void *param) } } - if (!amdgpu_in_reset(adev)) { + /* + * TODO: We need the lock to avoid touching DC state while it's being + * modified during automated compliance testing, or when link loss + * happens. While this should be split into subhandlers and proper + * interfaces to avoid having to conditionally lock like this in the + * outer layer, we need this workaround temporarily to allow MST + * lightup in some scenarios to avoid timeout. + */ + if (!amdgpu_in_reset(adev) && + (hpd_rx_irq_check_link_loss_status(dc_link, &hpd_irq_data) || + hpd_irq_data.bytes.device_service_irq.bits.AUTOMATED_TEST)) { mutex_lock(&adev->dm.dc_lock); + lock_flag = 1; + } + #ifdef CONFIG_DRM_AMD_DC_HDCP result = dc_link_handle_hpd_rx_irq(dc_link, &hpd_irq_data, NULL); #else result = dc_link_handle_hpd_rx_irq(dc_link, NULL, NULL); #endif + if (!amdgpu_in_reset(adev) && lock_flag) mutex_unlock(&adev->dm.dc_lock); - } out: if (result && !is_mst_root_connector) { diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c index 9e08410bfdfd5..32fb9cdbd9801 100644 --- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c +++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c @@ -2070,7 +2070,7 @@ enum dc_status read_hpd_rx_irq_data( return retval; } -static bool hpd_rx_irq_check_link_loss_status( +bool hpd_rx_irq_check_link_loss_status( struct dc_link *link, union hpd_irq_data *hpd_irq_dpcd_data) { diff --git a/drivers/gpu/drm/amd/display/dc/inc/dc_link_dp.h b/drivers/gpu/drm/amd/display/dc/inc/dc_link_dp.h index ffc3f2c63db84..7dd8bca542b96 100644 --- a/drivers/gpu/drm/amd/display/dc/inc/dc_link_dp.h +++ b/drivers/gpu/drm/amd/display/dc/inc/dc_link_dp.h @@ -68,6 +68,10 @@ bool perform_link_training_with_retries( enum signal_type signal, bool do_fallback); +bool hpd_rx_irq_check_link_loss_status( + struct dc_link *link, + union hpd_irq_data *hpd_irq_dpcd_data); + bool is_mst_supported(struct dc_link *link); bool detect_dp_sink_caps(struct dc_link *link); -- 2.39.5