Re: [PATCH 10/12] drm: bridge/dw_hdmi: fix phy enable/disable handling

[Yakir Yang <ykk@rock-chips.com>]

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On 10/07/2015 05:48 PM, Russell King - ARM Linux wrote:
> On Wed, Oct 07, 2015 at 12:05:37PM +0800, Yakir Yang wrote:
>>
>> On 08/09/2015 12:04 AM, Russell King wrote:
>>> The dw_hdmi enable/disable handling is particularly weak in several
>>> regards:
>>> * The hotplug interrupt could call hdmi_poweron() or hdmi_poweroff()
>>>    while DRM is setting a mode, which could race with a mode being set.
>>> * Hotplug will always re-enable the phy whenever it detects an active
>>>    hotplug signal, even if DRM has disabled the output.
>>>
>>> Resolve all of these by introducing a mutex to prevent races, and a
>>> state-tracking bool so we know whether DRM wishes the output to be
>>> enabled.  We choose to use our own mutex rather than ->struct_mutex
>>> so that we can still process interrupts in a timely fashion.
>>>
>>> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
>>> ---
>>>   drivers/gpu/drm/bridge/dw_hdmi.c | 29 ++++++++++++++++++++++-------
>>>   1 file changed, 22 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/bridge/dw_hdmi.c b/drivers/gpu/drm/bridge/dw_hdmi.c
>>> index 7b8a4e942a71..0ee188930d26 100644
>>> --- a/drivers/gpu/drm/bridge/dw_hdmi.c
>>> +++ b/drivers/gpu/drm/bridge/dw_hdmi.c
>>> @@ -125,6 +125,9 @@ struct dw_hdmi {
>>>   	bool sink_is_hdmi;
>>>   	bool sink_has_audio;
>>> +	struct mutex mutex;		/* for state below and previous_mode */
>>> +	bool disabled;			/* DRM has disabled our bridge */
>>> +
>>>   	spinlock_t audio_lock;
>>>   	struct mutex audio_mutex;
>>>   	unsigned int sample_rate;
>>> @@ -1389,8 +1392,12 @@ static void dw_hdmi_bridge_mode_set(struct drm_bridge *bridge,
>>>   {
>>>   	struct dw_hdmi *hdmi = bridge->driver_private;
>>> +	mutex_lock(&hdmi->mutex);
>>> +
>>>   	/* Store the display mode for plugin/DKMS poweron events */
>>>   	memcpy(&hdmi->previous_mode, mode, sizeof(hdmi->previous_mode));
>>> +
>>> +	mutex_unlock(&hdmi->mutex);
>>>   }
>>>   static bool dw_hdmi_bridge_mode_fixup(struct drm_bridge *bridge,
>>> @@ -1404,14 +1411,20 @@ static void dw_hdmi_bridge_disable(struct drm_bridge *bridge)
>>>   {
>>>   	struct dw_hdmi *hdmi = bridge->driver_private;
>>> +	mutex_lock(&hdmi->mutex);
>>> +	hdmi->disabled = true;
>>>   	dw_hdmi_poweroff(hdmi);
>>> +	mutex_unlock(&hdmi->mutex);
>>>   }
>>>   static void dw_hdmi_bridge_enable(struct drm_bridge *bridge)
>>>   {
>>>   	struct dw_hdmi *hdmi = bridge->driver_private;
>>> +	mutex_lock(&hdmi->mutex);
>>>   	dw_hdmi_poweron(hdmi);
>>> +	hdmi->disabled = false;
>>> +	mutex_unlock(&hdmi->mutex);
>>>   }
>>>   static void dw_hdmi_bridge_nop(struct drm_bridge *bridge)
>>> @@ -1534,20 +1547,20 @@ static irqreturn_t dw_hdmi_irq(int irq, void *dev_id)
>>>   	phy_int_pol = hdmi_readb(hdmi, HDMI_PHY_POL0);
>>>   	if (intr_stat & HDMI_IH_PHY_STAT0_HPD) {
>>> +		hdmi_modb(hdmi, ~phy_int_pol, HDMI_PHY_HPD, HDMI_PHY_POL0);
>>> +		mutex_lock(&hdmi->mutex);
>>>   		if (phy_int_pol & HDMI_PHY_HPD) {
>>>   			dev_dbg(hdmi->dev, "EVENT=plugin\n");
>>> -			hdmi_modb(hdmi, 0, HDMI_PHY_HPD, HDMI_PHY_POL0);
>>> -
>>> -			dw_hdmi_poweron(hdmi);
>>> +			if (!hdmi->disabled)
>>> +				dw_hdmi_poweron(hdmi);
>>>   		} else {
>>>   			dev_dbg(hdmi->dev, "EVENT=plugout\n");
>>> -			hdmi_modb(hdmi, HDMI_PHY_HPD, HDMI_PHY_HPD,
>>> -				  HDMI_PHY_POL0);
>>> -
>>> -			dw_hdmi_poweroff(hdmi);
>>> +			if (!hdmi->disabled)
>>> +				dw_hdmi_poweroff(hdmi);
>> Just like my reply on 08/12, I thought this could be removed, so
>> poweron/poweroff would only be called with bridge->enable/
>> bridge->disable, them maybe no need mutex here.
> The bridge enable/disable methods do not get called on hotplug changes.
>
> [    1.363011] dwhdmi-imx 120000.hdmi: Detected HDMI controller 0x13:0xa:0xa0:0xc1
> [    1.371341] dwhdmi-imx 120000.hdmi: dw_hdmi_irq(I:RX----,HPD P:RX3210,HPD S:RX----,HPD)
> [    1.381345] imx-drm display-subsystem: bound 120000.hdmi (ops dw_hdmi_imx_ops)
> [    1.448691] dwhdmi-imx 120000.hdmi: dw_hdmi_bridge_disable()
> [    1.450963] dwhdmi-imx 120000.hdmi: dw_hdmi_bridge_enable()
>
> and then unplugging and re-plugging the HDMI cable:
>
> [   68.307505] dwhdmi-imx 120000.hdmi: dw_hdmi_irq(I:RX----,HPD P:RX3210,--- S:RX----,---)
> [   73.813970] dwhdmi-imx 120000.hdmi: dw_hdmi_irq(I:RX----,HPD P:RX3210,HPD S:RX----,HPD)
>
> As you can see, during the period of disconnection for five seconds,
> dw_hdmi_bridge_disable() was not called.
>
> So, without the code above, we'd be needlessly wasting power with the
> bridge enabled, trying to drive a disconnected display.

Strangely, I do see bridge enable/disable in my side, past the log and 
dump_stack bellow.

And I guess your HDMI maybe not really hot pluged, could you confirm 
that the "status"
of HDMI display card have been changed between "connected" and 
"disconnected".


Do see bridge_disable when I unpluging the HDMI cable
[   16.358717] dwhdmi-rockchip ff980000.hdmi: EVENT=plugout
[   20.613221] [<c010e030>] (unwind_backtrace) from [<c010a4e0>] 
(show_stack+0x20/0x24)
[   20.631561] [<c010a4e0>] (show_stack) from [<c0896828>] 
(dump_stack+0x70/0x8c)
[   20.649337] [<c0896828>] (dump_stack) from [<c0414038>] 
(dw_hdmi_bridge_disable+0x1c/0x88)
[   20.668178] [<c0414038>] (dw_hdmi_bridge_disable) from [<c03e3888>] 
(drm_encoder_disable+0x34/0x78)
[   20.687857] [<c03e3888>] (drm_encoder_disable) from [<c03e3b1c>] 
(__drm_helper_disable_unused_functions+0x68/0xe4)
[   20.708975] [<c03e3b1c>] (__drm_helper_disable_unused_functions) from 
[<c03e4320>] (drm_crtc_helper_set_config+0x128/0x85c)
[   20.731180] [<c03e4320>] (drm_crtc_helper_set_config) from 
[<c03f5e3c>] (drm_mode_set_config_internal+0x58/0xdc)
[   20.752507] [<c03f5e3c>] (drm_mode_set_config_internal) from 
[<c0405ed0>] (commit_crtc_state+0x124/0x1ec)
[   20.773342] [<c0405ed0>] (commit_crtc_state) from [<c04055d4>] 
(atomic_commit.isra.3+0x5c/0xc8)
[   20.793397] [<c04055d4>] (atomic_commit.isra.3) from [<c040565c>] 
(drm_atomic_commit+0x1c/0x20)
[   20.813467] [<c040565c>] (drm_atomic_commit) from [<c03fa480>] 
(drm_mode_setcrtc+0x324/0x3e4)
[   20.833379] [<c03fa480>] (drm_mode_setcrtc) from [<c03eb320>] 
(drm_ioctl+0x304/0x478)
[   20.852557] [<c03eb320>] (drm_ioctl) from [<c021f024>] 
(do_vfs_ioctl+0x494/0x5a8)
[   20.871377] [<c021f024>] (do_vfs_ioctl) from [<c021f194>] 
(SyS_ioctl+0x5c/0x84)
[   20.890038] [<c021f194>] (SyS_ioctl) from [<c010646c>] 
(__sys_trace_return+0x0/0x14)
[   16.890157] ------- YAKIR: dw_hdmi_bridge_disable:1656
[   16.897907] ------- YAKIR: dw_hdmi_poweroff:1631

Also see bridge have been disabled once before try to bridge_enable when 
I try re-plugging the HDMI cable
[   20.494292] dwhdmi-rockchip ff980000.hdmi: EVENT=plugin
[   12.599389] [<c010e030>] (unwind_backtrace) from [<c010a4e0>] 
(show_stack+0x20/0x24)
[   12.612238] [<c010a4e0>] (show_stack) from [<c0896828>] 
(dump_stack+0x70/0x8c)
[   12.624609] [<c0896828>] (dump_stack) from [<c0414038>] 
(dw_hdmi_bridge_disable+0x1c/0x88)
[   12.638055] [<c0414038>] (dw_hdmi_bridge_disable) from [<c03e3dd4>] 
(drm_crtc_helper_set_mode+0x20c/0x4e0)
[   12.652878] [<c03e3dd4>] (drm_crtc_helper_set_mode) from [<c03e47ec>] 
(drm_crtc_helper_set_config+0x5f4/0x85c)
[   12.668019] [<c03e47ec>] (drm_crtc_helper_set_config) from 
[<c03f5e3c>] (drm_mode_set_config_internal+0x58/0xdc)
[   12.683442] [<c03f5e3c>] (drm_mode_set_config_internal) from 
[<c0405ed0>] (commit_crtc_state+0x124/0x1ec)
[   12.698287] [<c0405ed0>] (commit_crtc_state) from [<c04055d4>] 
(atomic_commit.isra.3+0x5c/0xc8)
[   12.712295] [<c04055d4>] (atomic_commit.isra.3) from [<c040565c>] 
(drm_atomic_commit+0x1c/0x20)
[   12.726258] [<c040565c>] (drm_atomic_commit) from [<c03fa480>] 
(drm_mode_setcrtc+0x324/0x3e4)
[   12.740226] [<c03fa480>] (drm_mode_setcrtc) from [<c03eb320>] 
(drm_ioctl+0x304/0x478)
[   12.753651] [<c03eb320>] (drm_ioctl) from [<c021f024>] 
(do_vfs_ioctl+0x494/0x5a8)
[   12.766794] [<c021f024>] (do_vfs_ioctl) from [<c021f194>] 
(SyS_ioctl+0x5c/0x84)
[   12.779861] [<c021f194>] (SyS_ioctl) from [<c010646c>] 
(__sys_trace_return+0x0/0x14)
[   21.059320] ------- YAKIR: dw_hdmi_bridge_disable:1656
[   21.068272] ------- YAKIR: dw_hdmi_poweroff:1631
[   21.076714] rockchip-vop ff930000.vop: start latency exceeded, new 
value 9333 ns
[   21.088037] rockchip-vop ff930000.vop: Attached to iommu domain
[   12.871336] [<c010e030>] (unwind_backtrace) from [<c010a4e0>] 
(show_stack+0x20/0x24)
[   12.882067] [<c010a4e0>] (show_stack) from [<c0896828>] 
(dump_stack+0x70/0x8c)
[   12.892311] [<c0896828>] (dump_stack) from [<c0414134>] 
(dw_hdmi_bridge_enable+0x3c/0xf28)
[   12.903569] [<c0414134>] (dw_hdmi_bridge_enable) from [<c03e3ff4>] 
(drm_crtc_helper_set_mode+0x42c/0x4e0)
[   12.916226] [<c03e3ff4>] (drm_crtc_helper_set_mode) from [<c03e47ec>] 
(drm_crtc_helper_set_config+0x5f4/0x85c)
[   12.929450] [<c03e47ec>] (drm_crtc_helper_set_config) from 
[<c03f5e3c>] (drm_mode_set_config_internal+0x58/0xdc)
[   12.942883] [<c03f5e3c>] (drm_mode_set_config_internal) from 
[<c0405ed0>] (commit_crtc_state+0x124/0x1ec)
[   12.955784] [<c0405ed0>] (commit_crtc_state) from [<c04055d4>] 
(atomic_commit.isra.3+0x5c/0xc8)
[   12.967753] [<c04055d4>] (atomic_commit.isra.3) from [<c040565c>] 
(drm_atomic_commit+0x1c/0x20)
[   12.979705] [<c040565c>] (drm_atomic_commit) from [<c03fa480>] 
(drm_mode_setcrtc+0x324/0x3e4)
[   12.991568] [<c03fa480>] (drm_mode_setcrtc) from [<c03eb320>] 
(drm_ioctl+0x304/0x478)
[   13.002817] [<c03eb320>] (drm_ioctl) from [<c021f024>] 
(do_vfs_ioctl+0x494/0x5a8)
[   13.013766] [<c021f024>] (do_vfs_ioctl) from [<c021f194>] 
(SyS_ioctl+0x5c/0x84)
[   13.024655] [<c021f194>] (SyS_ioctl) from [<c010646c>] 
(__sys_trace_return+0x0/0x14)
[   21.114556] ------- YAKIR: dw_hdmi_bridge_enable:1664
[   21.122889] ------- YAKIR: dw_hdmi_poweron:1625


- Yakir


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