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Specifically if the kernel has the DP AUX character device enabled and userspace accesses "/dev/drm_dp_auxN" directly then the AUX transfer function will be called regardless of whether a DP device is connected. For eDP panels we have a special rule where we wait (with a 5 second timeout) for HPD to go high. This rule was important before all panels drivers were converted to call wait_hpd_asserted() and actually can be removed in a future commit. For external DP devices we never checked for HPD. That means that trying to access the DP AUX character device (AKA `hexdump -C /dev/drm_dp_auxN`) would very, very slowly timeout. Specifically on my system: $ time hexdump -C /dev/drm_dp_aux0 hexdump: /dev/drm_dp_aux0: Connection timed out real 0m8.200s Let's add a check for HPD to avoid the slow timeout. This matches what, for instance, the intel_dp_aux_xfer() function does when it calls intel_tc_port_connected_locked(). That call has a document by it explaining that it's important to avoid the long timeouts. Fixes: c943b4948b58 ("drm/msm/dp: add displayPort driver support") Signed-off-by: Douglas Anderson --- drivers/gpu/drm/msm/dp/dp_aux.c | 8 +++++++- drivers/gpu/drm/msm/dp/dp_catalog.c | 10 ++++++++++ drivers/gpu/drm/msm/dp/dp_catalog.h | 1 + 3 files changed, 18 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/msm/dp/dp_aux.c b/drivers/gpu/drm/msm/dp/dp_aux.c index 03f4951c49f4..de0b0eabced9 100644 --- a/drivers/gpu/drm/msm/dp/dp_aux.c +++ b/drivers/gpu/drm/msm/dp/dp_aux.c @@ -307,7 +307,8 @@ static ssize_t dp_aux_transfer(struct drm_dp_aux *dp_aux, * turned on the panel and then tried to do an AUX transfer. The panel * driver has no way of knowing when the panel is ready, so it's up * to us to wait. For DP we never get into this situation so let's - * avoid ever doing the extra long wait for DP. + * avoid ever doing the extra long wait for DP and just query HPD + * directly. */ if (aux->is_edp) { ret = dp_catalog_aux_wait_for_hpd_connect_state(aux->catalog); @@ -315,6 +316,11 @@ static ssize_t dp_aux_transfer(struct drm_dp_aux *dp_aux, DRM_DEBUG_DP("Panel not ready for aux transactions\n"); goto exit; } + } else { + if (!dp_catalog_aux_is_hpd_connected(aux->catalog)) { + ret = -ENXIO; + goto exit; + } } dp_aux_update_offset_and_segment(aux, msg); diff --git a/drivers/gpu/drm/msm/dp/dp_catalog.c b/drivers/gpu/drm/msm/dp/dp_catalog.c index 5142aeb705a4..93e2d413a1e7 100644 --- a/drivers/gpu/drm/msm/dp/dp_catalog.c +++ b/drivers/gpu/drm/msm/dp/dp_catalog.c @@ -266,6 +266,16 @@ int dp_catalog_aux_wait_for_hpd_connect_state(struct dp_catalog *dp_catalog) 2000, 500000); } +bool dp_catalog_aux_is_hpd_connected(struct dp_catalog *dp_catalog) +{ + struct dp_catalog_private *catalog = container_of(dp_catalog, + struct dp_catalog_private, dp_catalog); + + /* poll for hpd connected status every 2ms and timeout after 500ms */ + return readl(catalog->io->dp_controller.aux.base + REG_DP_DP_HPD_INT_STATUS) & + DP_DP_HPD_STATE_STATUS_CONNECTED; +} + static void dump_regs(void __iomem *base, int len) { int i; diff --git a/drivers/gpu/drm/msm/dp/dp_catalog.h b/drivers/gpu/drm/msm/dp/dp_catalog.h index 38786e855b51..1694040c530f 100644 --- a/drivers/gpu/drm/msm/dp/dp_catalog.h +++ b/drivers/gpu/drm/msm/dp/dp_catalog.h @@ -86,6 +86,7 @@ void dp_catalog_aux_reset(struct dp_catalog *dp_catalog); void dp_catalog_aux_enable(struct dp_catalog *dp_catalog, bool enable); void dp_catalog_aux_update_cfg(struct dp_catalog *dp_catalog); int dp_catalog_aux_wait_for_hpd_connect_state(struct dp_catalog *dp_catalog); +bool dp_catalog_aux_is_hpd_connected(struct dp_catalog *dp_catalog); u32 dp_catalog_aux_get_irq(struct dp_catalog *dp_catalog); /* DP Controller APIs */