Re: [PATCH v11 1/4] drm/msm/dp: do not initialize phy until plugin interrupt received

From: Kuogee Hsieh
Date: Wed Jan 12 2022 - 17:18:03 EST

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In reply to: Stephen Boyd: "Re: [PATCH v11 1/4] drm/msm/dp: do not initialize phy until plugin interrupt received"
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On 1/12/2022 12:00 PM, Stephen Boyd wrote:

Quoting Kuogee Hsieh (2022-01-11 10:43:23)

Current DP drivers have regulators, clocks, irq and phy are grouped
together within a function and executed not in a symmetric manner.
This increase difficulty of code maintenance and limited code scalability.
This patch divides the driver life cycle of operation into four states,
resume (including booting up), dongle plugin, dongle unplugged and suspend.
Regulators, core clocks and irq are grouped together and enabled at resume
(or booting up) so that the DP controller is armed and ready to receive HPD
plugin interrupts. HPD plugin interrupt is generated when a dongle plugs
into DUT (device under test). Once HPD plugin interrupt is received, DP
controller will initialize phy so that dpcd read/write will function and
following link training can be proceeded successfully. DP phy will be
disabled after main link is teared down at end of unplugged HPD interrupt
handle triggered by dongle unplugged out of DUT. Finally regulators, code
clocks and irq are disabled at corresponding suspension.

0) Please note that dongles are behavior differently.

1) Apple dongle will generate plug-in interrupt only if no hdmi monitor atatched to dongle. it will generate irq-hpd interrupt once hdmi monitor connect to dongle later.

2) Apple dongle will generate plugged-in interrupt followed by irq-hpd interrupt if dongle has hdmi monitor attached when connects to DUT.

3) other dongle will not generate plug-in interrupt unless dongle has hdmi monitor attached when connects to DUT. It only generate plug-in interrupt only and no irq-hpd interrupt generated on this case.

4) Note: phy_initialized only associated with plugged-in interrupt

5) irq-hpd interrupt must happen after plugged-in interrupt and before unplugged interrupt

I will fill up below question with Apple dongle case with the order of event happen timing.

I'll write out the various scenarios

#1
dongle plugged in with HDMI cable attached
driver probe

1) driver probe ==> core_initialized = false; phy_initialized = false;
2) dp_display_host_init() ==> core_initialized = true;
3) generate plugged-in interrupt triggers handler
4) dp_display_phy_init() ==> phy_initialized = true;

#2
dongle unplugged
driver probe

1) driver probe ==> core_initialized = false; phy_initialized = false;
2) dp_display_host_init() ==> core_initialized = true;

#3
dongle plugged in without HDMI cable attached
driver probe

1) driver probe ==> core_initialized = false; phy_initialized = false;
2) dp_display_host_init() ==> core_initialized = true;
3) generate plug-in interrupt triggers handler
4) dp_display_phy_init() ==> phy_initialized = true;

Note: same as case #1

#4
driver probe
dongle plugged in without HDMI cable attached

#5
driver probe
dongle plugged in with HDMI cable attached

#6
driver probe
dongle plugged in
suspend
resume

1) driver probe ==> core_initialized = false; phy_initialized = false;
2) dp_display_host_init() ==> core_initialized = true;
3) dongle plug in
4) generate plug-in interrupt triggers handler
5) dp_display_phy_init() ==> phy_initialized = true;
6) suspend
7) dp_display_host_deinit() ==> core_initialized = false;
8) dp_display_host_phy_exit() ==> phy_initialize = false;
9) resume
10) dp_display_host_init() ==> core_initialized = true;
11) generate plug-in interrupt
12) dp_display_phy_init() ==> phy_initialize = true;

#7
driver probe
dongle plugged in
suspend
dongle unplugged
resume

1) driver probe ==> core_initialized = false; phy_initialized = false;
2) dp_display_host_init() ==> core_initialized = true;
3) dongle plugged in
4) generate plug-in interrupt triggers handler
5) dp_display_phy_init() ==> phy_initialized = true;
6) suspend
7) dp_display_host_deinit() ==> core_initialized = false;
8) dp_display_host_phy_exit() ==> phy_initialize = false;
9) dongle unplugged
10) resume
11) dp_display_host_init() ==> core_initialized = true;

#8
driver probe
dongle plugged in without HDMI cable attached
suspend
resume

1) driver probe ==> core_initialized = false; phy_initialized = false;
2) dp_display_host_init() ==> core_initialized = true;
3) dongle plug in
4) generate plug-in interrupt triggers handler
5) dp_display_phy_init() ==> phy_initialized = true;
6) suspend
7) dp_display_host_deinit() ==> core_initialized = false;
8) dp_display_host_phy_exit() ==> phy_initialize = false;
9) resume
10) dp_display_host_init() ==> core_initialized = true;
11) generate plug-in interrupt
12) dp_display_phy_init() ==> phy_initialize = true;

NOTE: same case #6

#9
driver probe
dongle plugged in without HDMI cable attached
suspend
HDMI cable attached during suspend
resume

1) driver probe ==> core_initialized = false; phy_initialized = false;
2) dp_display_host_init() ==> core_initialized = true;
3) dongle plugged in
4) generate plug-in interrupt triggers handler
5) dp_display_phy_init() ==> phy_initialized = true;
6) suspend
7) dp_display_host_deinit() ==> core_initialized = false;
8) dp_display_host_phy_exit() ==> phy_initialize = false;
9) HDMI cable attached
10) resume
11) dp_display_host_init() ==> core_initialized = true;
12) generate plug-in interrupt
13) dp_display_phy_init() ==> phy_initialize = true;

What's the state of the phy and core initialized variable at the end of
each of these scenarios? Please fill out the truth table.

+-----------------+------------------------
| false | true |
+-----------------+------------------------
phy_initialized | | |
+-----------------+------------------------
core_initialized | | #1, |
+-----------------+------------------------

I guess we also need eDP scenarios, but that's probably simpler

#10
eDP panel connected
driver probe

1) driver probe ==> core_initialized = false; phy_initialized = false;
2) dp_display_host_init() ==> core_initialized = true;
3) generate plug-in interrupt triggers handler
4) dp_display_phy_init() ==> phy_initialized = true;

#11
eDP panel disconnected
driver probe

NOTE: eDP panel can not be disconnected

#12
eDP panel disconnected
driver probe
suspend
resume

NOTE: assume edp panel connected
1) driver probe ==> core_initialized = false; phy_initialized = false;
2) dp_display_host_init() ==> core_initialized = true;
3) generate plug-in interrupt triggers handler
4) dp_display_phy_init() ==> phy_initialized = true;
5) suspend
6) dp_display_host_deinit() ==> core_initialized = false;
7) dp_display_host_phy_exit() ==> phy_initialize = false;
8) resume
9) dp_display_host_init() ==> core_initialized = true;
10) generate plug-in interrupt
11) dp_display_phy_init() ==> phy_initialize = true;

diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index 7cc4d21..f6bb4bc 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -83,6 +83,7 @@ struct dp_display_private {

/* state variables */
bool core_initialized;
+ bool phy_initialized;
bool hpd_irq_on;
bool audio_supported;

@@ -372,21 +373,46 @@ static int dp_display_process_hpd_high(struct dp_display_private *dp)
return rc;
}

-static void dp_display_host_init(struct dp_display_private *dp, int reset)
+static void dp_display_host_phy_init(struct dp_display_private *dp)
{
- bool flip = false;
+ DRM_DEBUG_DP("core_init=%d phy_init=%d\n",
+ dp->core_initialized, dp->phy_initialized);

+ if (!dp->phy_initialized) {
+ dp_ctrl_phy_init(dp->ctrl);
+ dp->phy_initialized = true;
+ }
+}
+
+static void dp_display_host_phy_exit(struct dp_display_private *dp)
+{
+ DRM_DEBUG_DP("core_init=%d phy_init=%d\n",
+ dp->core_initialized, dp->phy_initialized);
+
+ if (dp->phy_initialized) {
+ dp_ctrl_phy_exit(dp->ctrl);
+ dp->phy_initialized = false;
+ }
+}
+
+static void dp_display_host_init(struct dp_display_private *dp)
+{
DRM_DEBUG_DP("core_initialized=%d\n", dp->core_initialized);
if (dp->core_initialized) {
DRM_DEBUG_DP("DP core already initialized\n");
return;
}

- if (dp->usbpd->orientation == ORIENTATION_CC2)
- flip = true;
+ dp_power_init(dp->power, false);
+ dp_ctrl_reset_irq_ctrl(dp->ctrl, true);
+
+ /*
+ * eDP is the embedded primary display and has its own phy
+ * initialize phy immediately

Question still stands why we can't wait for hpd high from the eDP panel.
Also, I think "has its own phy" means that it's not part of a combo
USB+DP phy? Can you please clarify?

+ */
+ if (dp->dp_display.connector_type == DRM_MODE_CONNECTOR_eDP)
+ dp_display_host_phy_init(dp);

- dp_power_init(dp->power, flip);
- dp_ctrl_host_init(dp->ctrl, flip, reset);
dp_aux_init(dp->aux);
dp->core_initialized = true;
}
@@ -1306,20 +1330,23 @@ static int dp_pm_resume(struct device *dev)
dp->hpd_state = ST_DISCONNECTED;

/* turn on dp ctrl/phy */
- dp_display_host_init(dp, true);
+ dp_display_host_init(dp);

dp_catalog_ctrl_hpd_config(dp->catalog);

- /*
- * set sink to normal operation mode -- D0
- * before dpcd read
- */
- dp_link_psm_config(dp->link, &dp->panel->link_info, false);

if (dp_catalog_link_is_connected(dp->catalog)) {
+ /*
+ * set sink to normal operation mode -- D0
+ * before dpcd read
+ */
+ dp_display_host_phy_init(dp);
+ dp_link_psm_config(dp->link, &dp->panel->link_info, false);
sink_count = drm_dp_read_sink_count(dp->aux);
if (sink_count < 0)
sink_count = 0;
+
+ dp_display_host_phy_exit(dp);

Why is the phy exited on resume when the link is still connected? Is
this supposed to be done only when the sink_count is 0? And how does
this interact with eDP where the phy is initialized by the call to
dp_display_host_init() earlier in this function.

}

dp->link->sink_count = sink_count;
@@ -1366,6 +1393,8 @@ static int dp_pm_suspend(struct device *dev)
dp_display_host_deinit(dp);
}

+ dp_display_host_phy_exit(dp);
+
dp->hpd_state = ST_SUSPENDED;

/* host_init will be called at pm_resume */

Next message: Jens Axboe: "Re: [PATCH][RESEND] sata_fsl: Use struct_group() for memcpy() region"
Previous message: Nathan Chancellor: "Re: [PATCH v1 0/9] drivers: hv: dxgkrnl: Driver overview"
In reply to: Stephen Boyd: "Re: [PATCH v11 1/4] drm/msm/dp: do not initialize phy until plugin interrupt received"
Next in thread: Stephen Boyd: "Re: [PATCH v11 1/4] drm/msm/dp: do not initialize phy until plugin interrupt received"
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