[PATCH v2 0/6] drm/dp: i2c-over-aux short write support

[PATCH v2 0/6] drm/dp: i2c-over-aux short write support

[ville.syrjala]

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

I found these lying around in a branch. Most have r-b or ack from last time
[1] (the tegra patch doesn't). I also included the radeon 20bit AUX address
fix that seems to have fallen through the cracks as well.

I rebased these on top of my i2c-over-aux retry count series [2] since that
fixes a regression and so it's more urgent to get in.

[1] http://lists.freedesktop.org/archives/dri-devel/2015-March/079254.html
[2] http://lists.freedesktop.org/archives/dri-devel/2015-August/089250.html

Ville Syrjälä (6):
  drm/dp: s/I2C_STATUS/I2C_WRITE_STATUS_UPDATE/
  drm/i915: Handle DP_AUX_I2C_WRITE_STATUS_UPDATE
  drm/radeon: Handle DP_AUX_I2C_WRITE_STATUS_UPDATE
  drm/tegra: Handle I2C_WRITE_STATUS_UPDATE for address only writes
  drm/dp: Use I2C_WRITE_STATUS_UPDATE to drain partial I2C_WRITE
    requests
  drm/radeon: Send out the full AUX address

 drivers/gpu/drm/drm_dp_helper.c      | 43 ++++++++++++++++++++++++++++++++----
 drivers/gpu/drm/i915/intel_dp.c      |  1 +
 drivers/gpu/drm/radeon/atombios_dp.c |  6 +++--
 drivers/gpu/drm/tegra/dpaux.c        |  3 ++-
 include/drm/drm_dp_helper.h          |  2 +-
 5 files changed, 47 insertions(+), 8 deletions(-)

-- 
2.4.6

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[PATCH 1/6] drm/dp: s/I2C_STATUS/I2C_WRITE_STATUS_UPDATE/

[ville.syrjala]

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

Rename the I2C_STATUS request to I2C_WRITE_STATUS_UPDATE to match the
spec.

Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/tegra/dpaux.c | 2 +-
 include/drm/drm_dp_helper.h   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/tegra/dpaux.c b/drivers/gpu/drm/tegra/dpaux.c
index 224a7dc..1cc09ff 100644
--- a/drivers/gpu/drm/tegra/dpaux.c
+++ b/drivers/gpu/drm/tegra/dpaux.c
@@ -149,7 +149,7 @@ static ssize_t tegra_dpaux_transfer(struct drm_dp_aux *aux,
 
 		break;
 
-	case DP_AUX_I2C_STATUS:
+	case DP_AUX_I2C_WRITE_STATUS_UPDATE:
 		if (msg->request & DP_AUX_I2C_MOT)
 			value |= DPAUX_DP_AUXCTL_CMD_MOT_RQ;
 		else
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 499e9f6..d0c8810 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -46,7 +46,7 @@
 
 #define DP_AUX_I2C_WRITE		0x0
 #define DP_AUX_I2C_READ			0x1
-#define DP_AUX_I2C_STATUS		0x2
+#define DP_AUX_I2C_WRITE_STATUS_UPDATE	0x2
 #define DP_AUX_I2C_MOT			0x4
 #define DP_AUX_NATIVE_WRITE		0x8
 #define DP_AUX_NATIVE_READ		0x9
-- 
2.4.6

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[PATCH 2/6] drm/i915: Handle DP_AUX_I2C_WRITE_STATUS_UPDATE

[ville.syrjala]

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

When we get an i2c defer or short ack for i2c-over-aux write we need
to switch to WRITE_STATUS_UPDATE to poll for the completion of the
original request.

i915 doesn't try to interpret wht request type apart from separating
reads from writes, and so we should be able to treat this the same as
a normal i2c write.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 8a66a44..acd01da 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -974,6 +974,7 @@ intel_dp_aux_transfer(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
 	switch (msg->request & ~DP_AUX_I2C_MOT) {
 	case DP_AUX_NATIVE_WRITE:
 	case DP_AUX_I2C_WRITE:
+	case DP_AUX_I2C_WRITE_STATUS_UPDATE:
 		txsize = msg->size ? HEADER_SIZE + msg->size : BARE_ADDRESS_SIZE;
 		rxsize = 2; /* 0 or 1 data bytes */
 
-- 
2.4.6

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[PATCH 3/6] drm/radeon: Handle DP_AUX_I2C_WRITE_STATUS_UPDATE

[ville.syrjala]

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

When we get an i2c defer or short ack for i2c-over-aux write we need
to switch to WRITE_STATUS_UPDATE to poll for the completion of the
original request.

Looks like radeon doesn't do anything special with the request type,
so hopefully just treating it the same as a i2c write is enough.

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/radeon/atombios_dp.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/radeon/atombios_dp.c b/drivers/gpu/drm/radeon/atombios_dp.c
index f81e0d7..ca372c5 100644
--- a/drivers/gpu/drm/radeon/atombios_dp.c
+++ b/drivers/gpu/drm/radeon/atombios_dp.c
@@ -178,6 +178,7 @@ radeon_dp_aux_transfer_atom(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
 	switch (msg->request & ~DP_AUX_I2C_MOT) {
 	case DP_AUX_NATIVE_WRITE:
 	case DP_AUX_I2C_WRITE:
+	case DP_AUX_I2C_WRITE_STATUS_UPDATE:
 		/* The atom implementation only supports writes with a max payload of
 		 * 12 bytes since it uses 4 bits for the total count (header + payload)
 		 * in the parameter space.  The atom interface supports 16 byte
-- 
2.4.6

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[PATCH 4/6] drm/tegra: Handle I2C_WRITE_STATUS_UPDATE for address only writes

[ville.syrjala]

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

A address-only I2C_WRITE can't be replied with a short i2c ack, but I
suppose it could be replied with an i2c defer. So the code should be
prepared for an address-only I2C_WRITE_STATUS_UPDATE.

Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: "Terje Bergström" <tbergstrom@nvidia.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/tegra/dpaux.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/tegra/dpaux.c b/drivers/gpu/drm/tegra/dpaux.c
index 1cc09ff..6aecb66 100644
--- a/drivers/gpu/drm/tegra/dpaux.c
+++ b/drivers/gpu/drm/tegra/dpaux.c
@@ -119,6 +119,7 @@ static ssize_t tegra_dpaux_transfer(struct drm_dp_aux *aux,
 	 */
 	if (msg->size < 1) {
 		switch (msg->request & ~DP_AUX_I2C_MOT) {
+		case DP_AUX_I2C_WRITE_STATUS_UPDATE:
 		case DP_AUX_I2C_WRITE:
 		case DP_AUX_I2C_READ:
 			value = DPAUX_DP_AUXCTL_CMD_ADDRESS_ONLY;
-- 
2.4.6

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[PATCH 5/6] drm/dp: Use I2C_WRITE_STATUS_UPDATE to drain partial I2C_WRITE requests

[ville.syrjala]

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

When an i2c WRITE gets an i2c defer or short i2c ack reply, we are
supposed to switch the request from I2C_WRITE to I2C_WRITE_STATUS_UPDATE
when we continue to poll for the completion of the request.

v2: Don't assume DP_AUX_I2C_WRITE is 0 even though it is, to make the
    code more obvious to the casual reader (Jani)

Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/drm_dp_helper.c | 43 +++++++++++++++++++++++++++++++++++++----
 1 file changed, 39 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index ee5cd86..a717f4c 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -496,6 +496,27 @@ static int drm_dp_i2c_retry_count(const struct drm_dp_aux_msg *msg,
 	return DIV_ROUND_UP(i2c_len, aux_len + AUX_RETRY_INTERVAL);
 }
 
+static void drm_dp_i2c_msg_set_request(struct drm_dp_aux_msg *msg,
+				       const struct i2c_msg *i2c_msg)
+{
+	msg->request = (i2c_msg->flags & I2C_M_RD) ?
+		DP_AUX_I2C_READ : DP_AUX_I2C_WRITE;
+	msg->request |= DP_AUX_I2C_MOT;
+}
+
+static void drm_dp_i2c_msg_write_status_update(struct drm_dp_aux_msg *msg)
+{
+	/*
+	 * In case of i2c defer or short i2c ack reply to a write,
+	 * we need to switch to WRITE_STATUS_UPDATE to drain the
+	 * rest of the message
+	 */
+	if ((msg->request & ~DP_AUX_I2C_MOT) == DP_AUX_I2C_WRITE) {
+		msg->request &= DP_AUX_I2C_MOT;
+		msg->request |= DP_AUX_I2C_WRITE_STATUS_UPDATE;
+	}
+}
+
 /*
  * FIXME currently assumes 10 kHz as some real world devices seem
  * to require it. We should query/set the speed via DPCD if supported.
@@ -576,6 +597,8 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
 			 * Both native ACK and I2C ACK replies received. We
 			 * can assume the transfer was successful.
 			 */
+			if (ret != msg->size)
+				drm_dp_i2c_msg_write_status_update(msg);
 			return ret;
 
 		case DP_AUX_I2C_REPLY_NACK:
@@ -593,6 +616,7 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
 			if (defer_i2c < 7)
 				defer_i2c++;
 			usleep_range(AUX_RETRY_INTERVAL, AUX_RETRY_INTERVAL + 100);
+			drm_dp_i2c_msg_write_status_update(msg);
 			continue;
 
 		default:
@@ -658,10 +682,7 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
 
 	for (i = 0; i < num; i++) {
 		msg.address = msgs[i].addr;
-		msg.request = (msgs[i].flags & I2C_M_RD) ?
-			DP_AUX_I2C_READ :
-			DP_AUX_I2C_WRITE;
-		msg.request |= DP_AUX_I2C_MOT;
+		drm_dp_i2c_msg_set_request(&msg, &msgs[i]);
 		/* Send a bare address packet to start the transaction.
 		 * Zero sized messages specify an address only (bare
 		 * address) transaction.
@@ -669,6 +690,13 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
 		msg.buffer = NULL;
 		msg.size = 0;
 		err = drm_dp_i2c_do_msg(aux, &msg);
+
+		/*
+		 * Reset msg.request in case in case it got
+		 * changed into a WRITE_STATUS_UPDATE.
+		 */
+		drm_dp_i2c_msg_set_request(&msg, &msgs[i]);
+
 		if (err < 0)
 			break;
 		/* We want each transaction to be as large as possible, but
@@ -681,6 +709,13 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
 			msg.size = min(transfer_size, msgs[i].len - j);
 
 			err = drm_dp_i2c_drain_msg(aux, &msg);
+
+			/*
+			 * Reset msg.request in case in case it got
+			 * changed into a WRITE_STATUS_UPDATE.
+			 */
+			drm_dp_i2c_msg_set_request(&msg, &msgs[i]);
+
 			if (err < 0)
 				break;
 			transfer_size = err;
-- 
2.4.6

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[PATCH 6/6] drm/radeon: Send out the full AUX address

[ville.syrjala]

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

AUX addresses are 20 bits long. Send out the entire address instead of
just the low 16 bits.

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/radeon/atombios_dp.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/radeon/atombios_dp.c b/drivers/gpu/drm/radeon/atombios_dp.c
index ca372c5..bd73b40 100644
--- a/drivers/gpu/drm/radeon/atombios_dp.c
+++ b/drivers/gpu/drm/radeon/atombios_dp.c
@@ -171,8 +171,9 @@ radeon_dp_aux_transfer_atom(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
 		return -E2BIG;
 
 	tx_buf[0] = msg->address & 0xff;
-	tx_buf[1] = msg->address >> 8;
-	tx_buf[2] = msg->request << 4;
+	tx_buf[1] = (msg->address >> 8) & 0xff;
+	tx_buf[2] = (msg->request << 4) |
+		((msg->address >> 16) & 0xf);
 	tx_buf[3] = msg->size ? (msg->size - 1) : 0;
 
 	switch (msg->request & ~DP_AUX_I2C_MOT) {
-- 
2.4.6

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Re: [PATCH v2 0/6] drm/dp: i2c-over-aux short write support

[Jani Nikula]

On Thu, 27 Aug 2015, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> I found these lying around in a branch. Most have r-b or ack from last time
> [1] (the tegra patch doesn't). I also included the radeon 20bit AUX address
> fix that seems to have fallen through the cracks as well.
>
> I rebased these on top of my i2c-over-aux retry count series [2] since that
> fixes a regression and so it's more urgent to get in.

How about pushing both to a branch on some repo, and throwing them at
some of the bugs we have open?

BR,
Jani.

>
> [1] http://lists.freedesktop.org/archives/dri-devel/2015-March/079254.html
> [2] http://lists.freedesktop.org/archives/dri-devel/2015-August/089250.html
>
> Ville Syrjälä (6):
>   drm/dp: s/I2C_STATUS/I2C_WRITE_STATUS_UPDATE/
>   drm/i915: Handle DP_AUX_I2C_WRITE_STATUS_UPDATE
>   drm/radeon: Handle DP_AUX_I2C_WRITE_STATUS_UPDATE
>   drm/tegra: Handle I2C_WRITE_STATUS_UPDATE for address only writes
>   drm/dp: Use I2C_WRITE_STATUS_UPDATE to drain partial I2C_WRITE
>     requests
>   drm/radeon: Send out the full AUX address
>
>  drivers/gpu/drm/drm_dp_helper.c      | 43 ++++++++++++++++++++++++++++++++----
>  drivers/gpu/drm/i915/intel_dp.c      |  1 +
>  drivers/gpu/drm/radeon/atombios_dp.c |  6 +++--
>  drivers/gpu/drm/tegra/dpaux.c        |  3 ++-
>  include/drm/drm_dp_helper.h          |  2 +-
>  5 files changed, 47 insertions(+), 8 deletions(-)
>
> -- 
> 2.4.6
>
> _______________________________________________
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> dri-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
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Re: [PATCH v2 0/6] drm/dp: i2c-over-aux short write support

[Ville Syrjälä]

On Thu, Aug 27, 2015 at 05:34:45PM +0300, Jani Nikula wrote:
> On Thu, 27 Aug 2015, ville.syrjala@linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >
> > I found these lying around in a branch. Most have r-b or ack from last time
> > [1] (the tegra patch doesn't). I also included the radeon 20bit AUX address
> > fix that seems to have fallen through the cracks as well.
> >
> > I rebased these on top of my i2c-over-aux retry count series [2] since that
> > fixes a regression and so it's more urgent to get in.
> 
> How about pushing both to a branch on some repo, and throwing them at
> some of the bugs we have open?

Pushed the lot to: git://github.com/vsyrjala/linux.git i2c_aux_short_write_4

It's sitting top of drm-intel-nightly from a few days ago.

> 
> BR,
> Jani.
> 
> >
> > [1] http://lists.freedesktop.org/archives/dri-devel/2015-March/079254.html
> > [2] http://lists.freedesktop.org/archives/dri-devel/2015-August/089250.html
> >
> > Ville Syrjälä (6):
> >   drm/dp: s/I2C_STATUS/I2C_WRITE_STATUS_UPDATE/
> >   drm/i915: Handle DP_AUX_I2C_WRITE_STATUS_UPDATE
> >   drm/radeon: Handle DP_AUX_I2C_WRITE_STATUS_UPDATE
> >   drm/tegra: Handle I2C_WRITE_STATUS_UPDATE for address only writes
> >   drm/dp: Use I2C_WRITE_STATUS_UPDATE to drain partial I2C_WRITE
> >     requests
> >   drm/radeon: Send out the full AUX address
> >
> >  drivers/gpu/drm/drm_dp_helper.c      | 43 ++++++++++++++++++++++++++++++++----
> >  drivers/gpu/drm/i915/intel_dp.c      |  1 +
> >  drivers/gpu/drm/radeon/atombios_dp.c |  6 +++--
> >  drivers/gpu/drm/tegra/dpaux.c        |  3 ++-
> >  include/drm/drm_dp_helper.h          |  2 +-
> >  5 files changed, 47 insertions(+), 8 deletions(-)
> >
> > -- 
> > 2.4.6
> >
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
> -- 
> Jani Nikula, Intel Open Source Technology Center

-- 
Ville Syrjälä
Intel OTC
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Re: [PATCH 6/6] drm/radeon: Send out the full AUX address

[Alex Deucher]

On Thu, Aug 27, 2015 at 10:23 AM,  <ville.syrjala@linux.intel.com> wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> AUX addresses are 20 bits long. Send out the entire address instead of
> just the low 16 bits.
>
> Cc: Alex Deucher <alexander.deucher@amd.com>
> Cc: "Christian König" <christian.koenig@amd.com>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

Applied.  thanks!

Alex

> ---
>  drivers/gpu/drm/radeon/atombios_dp.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/radeon/atombios_dp.c b/drivers/gpu/drm/radeon/atombios_dp.c
> index ca372c5..bd73b40 100644
> --- a/drivers/gpu/drm/radeon/atombios_dp.c
> +++ b/drivers/gpu/drm/radeon/atombios_dp.c
> @@ -171,8 +171,9 @@ radeon_dp_aux_transfer_atom(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
>                 return -E2BIG;
>
>         tx_buf[0] = msg->address & 0xff;
> -       tx_buf[1] = msg->address >> 8;
> -       tx_buf[2] = msg->request << 4;
> +       tx_buf[1] = (msg->address >> 8) & 0xff;
> +       tx_buf[2] = (msg->request << 4) |
> +               ((msg->address >> 16) & 0xf);
>         tx_buf[3] = msg->size ? (msg->size - 1) : 0;
>
>         switch (msg->request & ~DP_AUX_I2C_MOT) {
> --
> 2.4.6
>
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Re: [PATCH 4/6] drm/tegra: Handle I2C_WRITE_STATUS_UPDATE for address only writes

[Thierry Reding]

[-- Attachment #1.1: Type: text/plain, Size: 643 bytes --]

On Thu, Aug 27, 2015 at 05:23:29PM +0300, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> A address-only I2C_WRITE can't be replied with a short i2c ack, but I
> suppose it could be replied with an i2c defer. So the code should be
> prepared for an address-only I2C_WRITE_STATUS_UPDATE.
> 
> Cc: Thierry Reding <thierry.reding@gmail.com>
> Cc: "Terje Bergström" <tbergstrom@nvidia.com>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/tegra/dpaux.c | 1 +
>  1 file changed, 1 insertion(+)

Acked-by: Thierry Reding <treding@nvidia.com>

[-- Attachment #1.2: signature.asc --]
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[-- Attachment #2: Type: text/plain, Size: 159 bytes --]

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Re: [PATCH 5/6] drm/dp: Use I2C_WRITE_STATUS_UPDATE to drain partial I2C_WRITE requests

[Daniel Vetter]

On Thu, Aug 27, 2015 at 05:23:30PM +0300, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> When an i2c WRITE gets an i2c defer or short i2c ack reply, we are
> supposed to switch the request from I2C_WRITE to I2C_WRITE_STATUS_UPDATE
> when we continue to poll for the completion of the request.
> 
> v2: Don't assume DP_AUX_I2C_WRITE is 0 even though it is, to make the
>     code more obvious to the casual reader (Jani)
> 
> Acked-by: Alex Deucher <alexander.deucher@amd.com>
> Reviewed-by: Jani Nikula <jani.nikula@intel.com>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

Applied patches 1-5 to drm-misc, thanks. Some minor context conflicts in
this one here that I resolved by juggling
drm_dp_i2c_msg_write_status_update a bit upwards.

Thanks, Daniel
> ---
>  drivers/gpu/drm/drm_dp_helper.c | 43 +++++++++++++++++++++++++++++++++++++----
>  1 file changed, 39 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index ee5cd86..a717f4c 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -496,6 +496,27 @@ static int drm_dp_i2c_retry_count(const struct drm_dp_aux_msg *msg,
>  	return DIV_ROUND_UP(i2c_len, aux_len + AUX_RETRY_INTERVAL);
>  }
>  
> +static void drm_dp_i2c_msg_set_request(struct drm_dp_aux_msg *msg,
> +				       const struct i2c_msg *i2c_msg)
> +{
> +	msg->request = (i2c_msg->flags & I2C_M_RD) ?
> +		DP_AUX_I2C_READ : DP_AUX_I2C_WRITE;
> +	msg->request |= DP_AUX_I2C_MOT;
> +}
> +
> +static void drm_dp_i2c_msg_write_status_update(struct drm_dp_aux_msg *msg)
> +{
> +	/*
> +	 * In case of i2c defer or short i2c ack reply to a write,
> +	 * we need to switch to WRITE_STATUS_UPDATE to drain the
> +	 * rest of the message
> +	 */
> +	if ((msg->request & ~DP_AUX_I2C_MOT) == DP_AUX_I2C_WRITE) {
> +		msg->request &= DP_AUX_I2C_MOT;
> +		msg->request |= DP_AUX_I2C_WRITE_STATUS_UPDATE;
> +	}
> +}
> +
>  /*
>   * FIXME currently assumes 10 kHz as some real world devices seem
>   * to require it. We should query/set the speed via DPCD if supported.
> @@ -576,6 +597,8 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
>  			 * Both native ACK and I2C ACK replies received. We
>  			 * can assume the transfer was successful.
>  			 */
> +			if (ret != msg->size)
> +				drm_dp_i2c_msg_write_status_update(msg);
>  			return ret;
>  
>  		case DP_AUX_I2C_REPLY_NACK:
> @@ -593,6 +616,7 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
>  			if (defer_i2c < 7)
>  				defer_i2c++;
>  			usleep_range(AUX_RETRY_INTERVAL, AUX_RETRY_INTERVAL + 100);
> +			drm_dp_i2c_msg_write_status_update(msg);
>  			continue;
>  
>  		default:
> @@ -658,10 +682,7 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
>  
>  	for (i = 0; i < num; i++) {
>  		msg.address = msgs[i].addr;
> -		msg.request = (msgs[i].flags & I2C_M_RD) ?
> -			DP_AUX_I2C_READ :
> -			DP_AUX_I2C_WRITE;
> -		msg.request |= DP_AUX_I2C_MOT;
> +		drm_dp_i2c_msg_set_request(&msg, &msgs[i]);
>  		/* Send a bare address packet to start the transaction.
>  		 * Zero sized messages specify an address only (bare
>  		 * address) transaction.
> @@ -669,6 +690,13 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
>  		msg.buffer = NULL;
>  		msg.size = 0;
>  		err = drm_dp_i2c_do_msg(aux, &msg);
> +
> +		/*
> +		 * Reset msg.request in case in case it got
> +		 * changed into a WRITE_STATUS_UPDATE.
> +		 */
> +		drm_dp_i2c_msg_set_request(&msg, &msgs[i]);
> +
>  		if (err < 0)
>  			break;
>  		/* We want each transaction to be as large as possible, but
> @@ -681,6 +709,13 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
>  			msg.size = min(transfer_size, msgs[i].len - j);
>  
>  			err = drm_dp_i2c_drain_msg(aux, &msg);
> +
> +			/*
> +			 * Reset msg.request in case in case it got
> +			 * changed into a WRITE_STATUS_UPDATE.
> +			 */
> +			drm_dp_i2c_msg_set_request(&msg, &msgs[i]);
> +
>  			if (err < 0)
>  				break;
>  			transfer_size = err;
> -- 
> 2.4.6
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

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