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

From: [email-masked] (Yakir Yang)
Date: Thu, 08 Oct 2015 16:35:22 +0800

Oh, I haven't noticed that those patches already have been
merged into linux-next  :-)

On 10/08/2015 03:17 AM, Russell King - ARM Linux wrote:
> On Wed, Oct 07, 2015 at 06:40:11PM +0800, Yakir Yang wrote:
>>
>> 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 <[email-masked]>
>>>>> ---
>>>>>   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".
> It does.
>
>> 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)
> Your userspace is issuing an ioctl to disable the output.  I guess you
> have other active outputs besides HDMI.
>
>

Yeah, I do have another active eDP screen, but after removed the eDP
display card, I still see the bridge enable/disabled have been called.

I try to track the some userspace code, but due to little knowledge about
ChomeOS code, still can't found something directly. As drm framework
won't make bridge disabled when connector plug out, so feel free to agree
this isn't duplicate work.

Thanks,
- Yakir