Re: [PATCH v2 3/3] drm/msm/dp: check main link status before start aux read

From: khsieh
Date: Thu Apr 15 2021 - 13:37:43 EST

On 2021-04-14 14:09, Stephen Boyd wrote:
Quoting Kuogee Hsieh (2021-04-13 16:11:44)
Make sure main link is in connection state before start aux
read/write operation to avoid unnecessary long delay due to
main link had been unplugged.

Signed-off-by: Kuogee Hsieh <khsieh@xxxxxxxxxxxxxx>
---
drivers/gpu/drm/msm/dp/dp_aux.c | 5 +++++
drivers/gpu/drm/msm/dp/dp_link.c | 20 +++++++++++++++-----
2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_aux.c b/drivers/gpu/drm/msm/dp/dp_aux.c
index 7c22bfe..fae3806 100644
--- a/drivers/gpu/drm/msm/dp/dp_aux.c
+++ b/drivers/gpu/drm/msm/dp/dp_aux.c
@@ -343,6 +343,11 @@ static ssize_t dp_aux_transfer(struct drm_dp_aux *dp_aux,

mutex_lock(&aux->mutex);

+ if (!dp_catalog_link_is_connected(aux->catalog)) {
+ ret = -ETIMEDOUT;
+ goto unlock_exit;
+ }

I get a crash here sometimes when plugging and unplugging an apple HDMI
dongle during suspend/resume. I guess device power management
(dp_pm_suspend()) is happening in parallel with aux transfers from the
kthread. Why doesn't the aux communication start reporting NAKs once the
cable is disconnected?

[ 366.210058] hdmi-audio-codec hdmi-audio-codec.15.auto: calling
platform_pm_suspend+0x0/0x60 @ 7175, parent:
ae90000.displayport-controller
[ 366.222825] hdmi-audio-codec hdmi-audio-codec.15.auto:
platform_pm_suspend+0x0/0x60 returned 0 after 1 usecs
[ 366.232939] msm-dp-display ae90000.displayport-controller: calling
dp_pm_suspend+0x0/0x80 @ 7175, parent: ae00000.mdss
[ 366.244006] msm-dp-display ae90000.displayport-controller:
dp_pm_suspend+0x0/0x80 returned 0 after 79 usecs
[ 366.254025] msm_dsi ae94000.dsi: calling
pm_runtime_force_suspend+0x0/0xb4 @ 7175, parent: ae00000.mdss
[ 366.263669] msm_dsi ae94000.dsi: pm_runtime_force_suspend+0x0/0xb4
returned 0 after 0 usecs
[ 366.272290] panel-simple panel: calling
platform_pm_suspend+0x0/0x60 @ 7175, parent: platform
[ 366.272501] ti_sn65dsi86 2-002d: calling
pm_runtime_force_suspend+0x0/0xb4 @ 176, parent: i2c-2
[ 366.281055] panel-simple panel: platform_pm_suspend+0x0/0x60
returned 0 after 0 usecs
[ 366.281081] leds mmc1::: calling led_suspend+0x0/0x4c @ 7175,
parent: 7c4000.sdhci
[ 366.290065] ti_sn65dsi86 2-002d: pm_runtime_force_suspend+0x0/0xb4
returned 0 after 0 usecs
[ 366.298046] leds mmc1::: led_suspend+0x0/0x4c returned 0 after 1 usecs
[ 366.302994] Internal error: synchronous external abort: 96000010
[#1] PREEMPT SMP
[ 366.303006] Modules linked in: vhost_vsock
vmw_vsock_virtio_transport_common vsock vhost rfcomm algif_hash
algif_skcipher af_alg xt_cgroup uinput xt_MASQUERADE venus_enc
hci_uart venus_dec btqca cros_ec_typec typec bluetooth qcom_spmi_adc5
snd_soc_sc7180 qcom_spmi_temp_alarm ecdh_generic qcom_spmi_adc_tm5
qcom_vadc_common snd_soc_qcom_common ecc snd_soc_rt5682_i2c
snd_soc_rt5682 snd_soc_rl6231 venus_core v4l2_mem2mem
snd_soc_lpass_sc7180 snd_soc_lpass_hdmi snd_soc_lpass_cpu
snd_soc_lpass_platform snd_soc_max98357a fuse iio_trig_sysfs
cros_ec_sensors cros_ec_sensors_ring cros_ec_lid_angle
cros_ec_sensors_core industrialio_triggered_buffer kfifo_buf
cros_ec_sensorhub lzo_rle lzo_compress zram ath10k_snoc ath10k_core
ath mac80211 cfg80211 cdc_ether usbnet r8152 mii uvcvideo
videobuf2_vmalloc joydev
[ 366.303211] CPU: 0 PID: 224 Comm: dp_hpd_handler Not tainted 5.4.109 #27
[ 366.303216] Hardware name: Google Lazor (rev3+) with KB Backlight (DT)
[ 366.303225] pstate: 60c00009 (nZCv daif +PAN +UAO)
[ 366.303234] pc : dp_catalog_link_is_connected+0x20/0x34
[ 366.303244] lr : dp_aux_transfer+0x44/0x284
[ 366.303250] sp : ffffffc011bfbbe0
[ 366.303254] x29: ffffffc011bfbbe0 x28: aaaaaaaaaaaaaaaa
[ 366.303262] x27: 000000000000000c x26: ffffff896f8212bc
[ 366.303269] x25: 0000000000000001 x24: 0000000000000001
[ 366.303275] x23: 0000000000000020 x22: ffffff896ff82118
[ 366.303282] x21: ffffffc011bfbc50 x20: ffffff896ff82090
[ 366.303289] x19: ffffff896ffc3598 x18: 0000000000000000
[ 366.303295] x17: 0000000000000000 x16: 0000000000000001
[ 366.303303] x15: 0000000000000000 x14: 00000000000002ef
[ 366.303311] x13: 0000000000000400 x12: ffffffeb896ea060
[ 366.303317] x11: 0000000000000000 x10: 0000000000000000
[ 366.303324] x9 : ffffff896f061100 x8 : ffffffc010582204
[ 366.303331] x7 : 000000b2b5593519 x6 : 00000000003033ff
[ 366.303338] x5 : 0000000000000000 x4 : 0000000000000001
[ 366.303345] x3 : ffffff896ff432a1 x2 : 0000000000000000
[ 366.303352] x1 : 0000000000000119 x0 : ffffff896ffc3598
[ 366.303360] Call trace:
[ 366.303367] dp_catalog_link_is_connected+0x20/0x34
[ 366.303374] dp_aux_transfer+0x44/0x284
[ 366.303387] drm_dp_dpcd_access+0x8c/0x11c
[ 366.303393] drm_dp_dpcd_read+0x64/0x10c
[ 366.303399] dp_link_process_request+0x94/0xaf8
[ 366.303405] dp_display_usbpd_attention_cb+0x38/0x140
[ 366.303411] hpd_event_thread+0x3f0/0x48c
[ 366.303426] kthread+0x140/0x17c
[ 366.303439] ret_from_fork+0x10/0x18
[ 366.303458] Code: d503201f f85f0268 f9400508 91081108 (b9400108)

it needs to make sure core clock enabled before access dp ctrl registers
I am look into it
+
aux->native = msg->request & (DP_AUX_NATIVE_WRITE & DP_AUX_NATIVE_READ);

/* Ignore address only message */
diff --git a/drivers/gpu/drm/msm/dp/dp_link.c b/drivers/gpu/drm/msm/dp/dp_link.c
index be986da..d35b18e 100644
--- a/drivers/gpu/drm/msm/dp/dp_link.c
+++ b/drivers/gpu/drm/msm/dp/dp_link.c
@@ -737,18 +737,25 @@ static int dp_link_parse_sink_count(struct dp_link *dp_link)
return 0;
}

-static void dp_link_parse_sink_status_field(struct dp_link_private *link)
+static int dp_link_parse_sink_status_field(struct dp_link_private *link)
{
int len = 0;

link->prev_sink_count = link->dp_link.sink_count;
- dp_link_parse_sink_count(&link->dp_link);
+ len = dp_link_parse_sink_count(&link->dp_link);
+ if (len < 0) {
+ DRM_ERROR("DP lparse sink count failed\n");

Is it 'lparse' on purpose?

+ return len;
+ }

len = drm_dp_dpcd_read_link_status(link->aux,
link->link_status);
- if (len < DP_LINK_STATUS_SIZE)
+ if (len < DP_LINK_STATUS_SIZE) {
DRM_ERROR("DP link status read failed\n");
- dp_link_parse_request(link);
+ return len;
+ }
+
+ return dp_link_parse_request(link);
}

/**
@@ -1032,7 +1039,10 @@ int dp_link_process_request(struct dp_link *dp_link)

dp_link_reset_data(link);

- dp_link_parse_sink_status_field(link);
+ ret = dp_link_parse_sink_status_field(link);
+ if (ret) {
+ return ret;
+ }

if (link->request.test_requested == DP_TEST_LINK_EDID_READ) {
dp_link->sink_request |= DP_TEST_LINK_EDID_READ;

These are probably good fixes on their own given that
dp_link_parse_sink_count() can return an error and that was being
ignored.