Early init drm_dp_aux for internal use before i2c-core is ready

Early init drm_dp_aux for internal use before i2c-core is ready

[Chris Wilson]

In order to break a chicken-and-egg problem in wanting to use
i2c_transfer on the drm_dp_aux before it is registered with userspace
(which is a requirement for i2c_add_adapter() sadly), we need to prepare
enough state internally so that drm_dp_aux->algo->master_xfer() is
operation. A trio of patches to expose this operation from i2c has been
sent, which we can plug in here to replace the open-coding. I want to
get the ball rolling on this as I have a regression fix pending getting
i915 init reordered.
-Chris

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[PATCH 1/2] drm: Pass the drm_dp_aux->hw_mutex to i2c for its locking

[Chris Wilson]

Rather than have both drm_dp_aux lock within its transfer, and i2c to
lock around the transfer, use the same lock by filling in the locking
callbacks that i2c wants to use. We require our own hw_mutex as we
bypass i2c_transfer for drm_dp_dpcd_access().

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Rafael Antognolli <rafael.antognolli@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: dri-devel@lists.freedesktop.org
---
 drivers/gpu/drm/drm_dp_helper.c | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index eeaf5a7c3aa7..4b088afa21b2 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -708,8 +708,6 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
 
 	memset(&msg, 0, sizeof(msg));
 
-	mutex_lock(&aux->hw_mutex);
-
 	for (i = 0; i < num; i++) {
 		msg.address = msgs[i].addr;
 		drm_dp_i2c_msg_set_request(&msg, &msgs[i]);
@@ -764,8 +762,6 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
 	msg.size = 0;
 	(void)drm_dp_i2c_do_msg(aux, &msg);
 
-	mutex_unlock(&aux->hw_mutex);
-
 	return err;
 }
 
@@ -774,6 +770,26 @@ static const struct i2c_algorithm drm_dp_i2c_algo = {
 	.master_xfer = drm_dp_i2c_xfer,
 };
 
+static struct drm_dp_aux *i2c_to_aux(struct i2c_adapter *i2c)
+{
+	return container_of(i2c, struct drm_dp_aux, ddc);
+}
+
+static void lock_bus(struct i2c_adapter *i2c, unsigned int flags)
+{
+	mutex_lock(&i2c_to_aux(i2c)->hw_mutex);
+}
+
+static int trylock_bus(struct i2c_adapter *i2c, unsigned int flags)
+{
+	return mutex_trylock(&i2c_to_aux(i2c)->hw_mutex);
+}
+
+static void unlock_bus(struct i2c_adapter *i2c, unsigned int flags)
+{
+	mutex_unlock(&i2c_to_aux(i2c)->hw_mutex);
+}
+
 /**
  * drm_dp_aux_register() - initialise and register aux channel
  * @aux: DisplayPort AUX channel
@@ -790,6 +806,10 @@ int drm_dp_aux_register(struct drm_dp_aux *aux)
 	aux->ddc.algo_data = aux;
 	aux->ddc.retries = 3;
 
+	aux->ddc.lock_bus = lock_bus;
+	aux->ddc.trylock_bus = trylock_bus;
+	aux->ddc.unlock_bus = unlock_bus;
+
 	aux->ddc.class = I2C_CLASS_DDC;
 	aux->ddc.owner = THIS_MODULE;
 	aux->ddc.dev.parent = aux->dev;
-- 
2.8.1

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[PATCH 2/2] drm: Minimally initialise drm_dp_aux

[Chris Wilson]

When trying to split up the initialisation phase and the registration
phase, one immediate problem encountered is trying to use our own i2c
devices before registration with userspace (to read EDID during device
discovery). drm_dp_aux in particular only offers an interface for setting
up the device *after* we have exposed the connector via sysfs. In order
to break the chicken-and-egg problem, export drm_dp_aux_init() to
minimally prepare the i2c device for internal use before
drm_connector_register().

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Rafael Antognolli <rafael.antognolli@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: dri-devel@lists.freedesktop.org
---
 drivers/gpu/drm/drm_dp_helper.c | 26 +++++++++++++++++++++-----
 include/drm/drm_dp_helper.h     |  1 +
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 4b088afa21b2..9b4ec65e1de6 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -791,15 +791,16 @@ static void unlock_bus(struct i2c_adapter *i2c, unsigned int flags)
 }
 
 /**
- * drm_dp_aux_register() - initialise and register aux channel
+ * drm_dp_aux_init() - minimally initialise an aux channel
  * @aux: DisplayPort AUX channel
  *
- * Returns 0 on success or a negative error code on failure.
+ * If you need to use the drm_dp_aux's i2c adapter prior to registering it
+ * with the outside world, call drm_dp_aux_init() first. You must still
+ * call drm_dp_aux_register() once the connector has been registered to
+ * allow userspace access to the auxiliary DP channel.
  */
-int drm_dp_aux_register(struct drm_dp_aux *aux)
+void drm_dp_aux_init(struct drm_dp_aux *aux)
 {
-	int ret;
-
 	mutex_init(&aux->hw_mutex);
 
 	aux->ddc.algo = &drm_dp_i2c_algo;
@@ -809,6 +810,21 @@ int drm_dp_aux_register(struct drm_dp_aux *aux)
 	aux->ddc.lock_bus = lock_bus;
 	aux->ddc.trylock_bus = trylock_bus;
 	aux->ddc.unlock_bus = unlock_bus;
+}
+EXPORT_SYMBOL(drm_dp_aux_init);
+
+/**
+ * drm_dp_aux_register() - initialise and register aux channel
+ * @aux: DisplayPort AUX channel
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+int drm_dp_aux_register(struct drm_dp_aux *aux)
+{
+	int ret;
+
+	if (!aux->ddc.algo)
+		drm_dp_aux_init(aux);
 
 	aux->ddc.class = I2C_CLASS_DDC;
 	aux->ddc.owner = THIS_MODULE;
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 5a848e734422..4d85cf2874af 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -805,6 +805,7 @@ int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link);
 int drm_dp_link_power_down(struct drm_dp_aux *aux, struct drm_dp_link *link);
 int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link);
 
+void drm_dp_aux_init(struct drm_dp_aux *aux);
 int drm_dp_aux_register(struct drm_dp_aux *aux);
 void drm_dp_aux_unregister(struct drm_dp_aux *aux);
 
-- 
2.8.1

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✗ Ro.CI.BAT: failure for series starting with [1/2] drm: Pass the drm_dp_aux->hw_mutex to i2c for its locking

[Patchwork]

== Series Details ==

Series: series starting with [1/2] drm: Pass the drm_dp_aux->hw_mutex to i2c for its locking
URL   : https://patchwork.freedesktop.org/series/8815/
State : failure

== Summary ==

Series 8815v1 Series without cover letter
http://patchwork.freedesktop.org/api/1.0/series/8815/revisions/1/mbox

Test kms_flip:
        Subgroup basic-flip-vs-wf_vblank:
                pass       -> FAIL       (ro-bdw-i7-5600u)
Test kms_pipe_crc_basic:
        Subgroup suspend-read-crc-pipe-a:
                pass       -> INCOMPLETE (fi-skl-i7-6700k)

fi-skl-i5-6260u  total:213  pass:202  dwarn:0   dfail:0   fail:0   skip:11 
fi-skl-i7-6700k  total:188  pass:164  dwarn:0   dfail:0   fail:0   skip:23 
ro-bdw-i5-5250u  total:213  pass:197  dwarn:1   dfail:0   fail:0   skip:15 
ro-bdw-i7-5557U  total:213  pass:198  dwarn:0   dfail:0   fail:0   skip:15 
ro-bdw-i7-5600u  total:213  pass:184  dwarn:0   dfail:0   fail:1   skip:28 
ro-bsw-n3050     total:213  pass:172  dwarn:0   dfail:0   fail:2   skip:39 
ro-byt-n2820     total:213  pass:173  dwarn:0   dfail:0   fail:3   skip:37 
ro-hsw-i3-4010u  total:213  pass:190  dwarn:0   dfail:0   fail:0   skip:23 
ro-hsw-i7-4770r  total:213  pass:190  dwarn:0   dfail:0   fail:0   skip:23 
ro-ilk-i7-620lm  total:213  pass:150  dwarn:0   dfail:0   fail:1   skip:62 
ro-ilk1-i5-650   total:208  pass:150  dwarn:0   dfail:0   fail:1   skip:57 
ro-ivb-i7-3770   total:213  pass:181  dwarn:0   dfail:0   fail:0   skip:32 
ro-ivb2-i7-3770  total:213  pass:185  dwarn:0   dfail:0   fail:0   skip:28 
ro-skl3-i5-6260u total:213  pass:201  dwarn:1   dfail:0   fail:0   skip:11 
ro-snb-i7-2620M  total:213  pass:174  dwarn:0   dfail:0   fail:1   skip:38 
fi-hsw-i7-4770k failed to connect after reboot

Results at /archive/results/CI_IGT_test/RO_Patchwork_1204/

1ed16fe drm-intel-nightly: 2016y-06m-17d-07h-46m-19s UTC integration manifest
1289c19 drm: Minimally initialise drm_dp_aux
39b4329 drm: Pass the drm_dp_aux->hw_mutex to i2c for its locking

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Re: [PATCH 2/2] drm: Minimally initialise drm_dp_aux

[Daniel Vetter]

On Fri, Jun 17, 2016 at 09:33:18AM +0100, Chris Wilson wrote:
> When trying to split up the initialisation phase and the registration
> phase, one immediate problem encountered is trying to use our own i2c
> devices before registration with userspace (to read EDID during device
> discovery). drm_dp_aux in particular only offers an interface for setting
> up the device *after* we have exposed the connector via sysfs. In order
> to break the chicken-and-egg problem, export drm_dp_aux_init() to
> minimally prepare the i2c device for internal use before
> drm_connector_register().
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Dave Airlie <airlied@redhat.com>
> Cc: Rafael Antognolli <rafael.antognolli@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: dri-devel@lists.freedesktop.org
> ---
>  drivers/gpu/drm/drm_dp_helper.c | 26 +++++++++++++++++++++-----
>  include/drm/drm_dp_helper.h     |  1 +
>  2 files changed, 22 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index 4b088afa21b2..9b4ec65e1de6 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -791,15 +791,16 @@ static void unlock_bus(struct i2c_adapter *i2c, unsigned int flags)
>  }
>  
>  /**
> - * drm_dp_aux_register() - initialise and register aux channel
> + * drm_dp_aux_init() - minimally initialise an aux channel
>   * @aux: DisplayPort AUX channel
>   *
> - * Returns 0 on success or a negative error code on failure.
> + * If you need to use the drm_dp_aux's i2c adapter prior to registering it
> + * with the outside world, call drm_dp_aux_init() first. You must still
> + * call drm_dp_aux_register() once the connector has been registered to
> + * allow userspace access to the auxiliary DP channel.
>   */
> -int drm_dp_aux_register(struct drm_dp_aux *aux)
> +void drm_dp_aux_init(struct drm_dp_aux *aux)
>  {
> -	int ret;
> -
>  	mutex_init(&aux->hw_mutex);
>  
>  	aux->ddc.algo = &drm_dp_i2c_algo;
> @@ -809,6 +810,21 @@ int drm_dp_aux_register(struct drm_dp_aux *aux)
>  	aux->ddc.lock_bus = lock_bus;
>  	aux->ddc.trylock_bus = trylock_bus;
>  	aux->ddc.unlock_bus = unlock_bus;
> +}
> +EXPORT_SYMBOL(drm_dp_aux_init);
> +
> +/**
> + * drm_dp_aux_register() - initialise and register aux channel
> + * @aux: DisplayPort AUX channel
> + *
> + * Returns 0 on success or a negative error code on failure.

I amended kerneldoc slightly here and merged both, thanks.
-Daniel

> + */
> +int drm_dp_aux_register(struct drm_dp_aux *aux)
> +{
> +	int ret;
> +
> +	if (!aux->ddc.algo)
> +		drm_dp_aux_init(aux);
>  
>  	aux->ddc.class = I2C_CLASS_DDC;
>  	aux->ddc.owner = THIS_MODULE;
> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> index 5a848e734422..4d85cf2874af 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -805,6 +805,7 @@ int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link);
>  int drm_dp_link_power_down(struct drm_dp_aux *aux, struct drm_dp_link *link);
>  int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link);
>  
> +void drm_dp_aux_init(struct drm_dp_aux *aux);
>  int drm_dp_aux_register(struct drm_dp_aux *aux);
>  void drm_dp_aux_unregister(struct drm_dp_aux *aux);
>  
> -- 
> 2.8.1
> 
> _______________________________________________
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> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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