[3/3] drm/msm/dp: Handle aux timeouts, nacks, defers

Message ID 20210507212505.1224111-4-swboyd@chromium.org
State New
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Series
  • drm/msm/dp: Simplify aux code
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Commit Message

Stephen Boyd May 7, 2021, 9:25 p.m.
Let's look at the irq status bits after a transfer and see if we got a
nack or a defer or a timeout, instead of telling drm layers that
everything was fine, while still printing an error message. I wasn't
sure about NACK+DEFER so I lumped all those various errors along with a
nack so that the drm core can figure out that things are just not going
well. The important thing is that we're now returning -ETIMEDOUT when
the message times out and nacks for bad addresses.

Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc: Abhinav Kumar <abhinavk@codeaurora.org>
Cc: Kuogee Hsieh <khsieh@codeaurora.org>
Cc: aravindh@codeaurora.org
Cc: Sean Paul <sean@poorly.run>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
---
 drivers/gpu/drm/msm/dp/dp_aux.c | 140 ++++++++++++++------------------
 drivers/gpu/drm/msm/dp/dp_aux.h |   8 --
 2 files changed, 61 insertions(+), 87 deletions(-)

Comments

Kuogee Hsieh May 24, 2021, 4:33 p.m. | #1
On 2021-05-07 14:25, Stephen Boyd wrote:
> Let's look at the irq status bits after a transfer and see if we got a

> nack or a defer or a timeout, instead of telling drm layers that

> everything was fine, while still printing an error message. I wasn't

> sure about NACK+DEFER so I lumped all those various errors along with a

> nack so that the drm core can figure out that things are just not going

> well. The important thing is that we're now returning -ETIMEDOUT when

> the message times out and nacks for bad addresses.

> 

> Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

> Cc: Abhinav Kumar <abhinavk@codeaurora.org>

> Cc: Kuogee Hsieh <khsieh@codeaurora.org>

> Cc: aravindh@codeaurora.org

> Cc: Sean Paul <sean@poorly.run>

> Signed-off-by: Stephen Boyd <swboyd@chromium.org>

> ---

>  drivers/gpu/drm/msm/dp/dp_aux.c | 140 ++++++++++++++------------------

>  drivers/gpu/drm/msm/dp/dp_aux.h |   8 --

>  2 files changed, 61 insertions(+), 87 deletions(-)

> 

> diff --git a/drivers/gpu/drm/msm/dp/dp_aux.c 

> b/drivers/gpu/drm/msm/dp/dp_aux.c

> index b49810396513..4a3293b590b0 100644

> --- a/drivers/gpu/drm/msm/dp/dp_aux.c

> +++ b/drivers/gpu/drm/msm/dp/dp_aux.c

> @@ -9,7 +9,15 @@

>  #include "dp_reg.h"

>  #include "dp_aux.h"

> 

> -#define DP_AUX_ENUM_STR(x)		#x

> +enum msm_dp_aux_err {

> +	DP_AUX_ERR_NONE,

> +	DP_AUX_ERR_ADDR,

> +	DP_AUX_ERR_TOUT,

> +	DP_AUX_ERR_NACK,

> +	DP_AUX_ERR_DEFER,

> +	DP_AUX_ERR_NACK_DEFER,

> +	DP_AUX_ERR_PHY,

> +};

> 

>  struct dp_aux_private {

>  	struct device *dev;

> @@ -18,7 +26,7 @@ struct dp_aux_private {

>  	struct mutex mutex;

>  	struct completion comp;

> 

> -	u32 aux_error_num;

> +	enum msm_dp_aux_err aux_error_num;

>  	u32 retry_cnt;

>  	bool cmd_busy;

>  	bool native;

> @@ -33,62 +41,45 @@ struct dp_aux_private {

> 

>  #define MAX_AUX_RETRIES			5

> 

> -static const char *dp_aux_get_error(u32 aux_error)

> -{

> -	switch (aux_error) {

> -	case DP_AUX_ERR_NONE:

> -		return DP_AUX_ENUM_STR(DP_AUX_ERR_NONE);

> -	case DP_AUX_ERR_ADDR:

> -		return DP_AUX_ENUM_STR(DP_AUX_ERR_ADDR);

> -	case DP_AUX_ERR_TOUT:

> -		return DP_AUX_ENUM_STR(DP_AUX_ERR_TOUT);

> -	case DP_AUX_ERR_NACK:

> -		return DP_AUX_ENUM_STR(DP_AUX_ERR_NACK);

> -	case DP_AUX_ERR_DEFER:

> -		return DP_AUX_ENUM_STR(DP_AUX_ERR_DEFER);

> -	case DP_AUX_ERR_NACK_DEFER:

> -		return DP_AUX_ENUM_STR(DP_AUX_ERR_NACK_DEFER);

> -	default:

> -		return "unknown";

> -	}

> -}

> -

> -static u32 dp_aux_write(struct dp_aux_private *aux,

> +static ssize_t dp_aux_write(struct dp_aux_private *aux,

>  			struct drm_dp_aux_msg *msg)

>  {

> -	u32 data[4], reg, len;

> +	u8 data[4];

> +	u32 reg;

> +	ssize_t len;

>  	u8 *msgdata = msg->buffer;

>  	int const AUX_CMD_FIFO_LEN = 128;

>  	int i = 0;

> 

>  	if (aux->read)

> -		len = 4;

> +		len = 0;

>  	else

> -		len = msg->size + 4;

> +		len = msg->size;

> 

>  	/*

>  	 * cmd fifo only has depth of 144 bytes

>  	 * limit buf length to 128 bytes here

>  	 */

> -	if (len > AUX_CMD_FIFO_LEN) {

> +	if (len > AUX_CMD_FIFO_LEN - 4) {

>  		DRM_ERROR("buf size greater than allowed size of 128 bytes\n");

> -		return 0;

> +		return -EINVAL;

>  	}

> 

>  	/* Pack cmd and write to HW */

> -	data[0] = (msg->address >> 16) & 0xf; /* addr[19:16] */

> +	data[0] = (msg->address >> 16) & 0xf;	/* addr[19:16] */

>  	if (aux->read)

> -		data[0] |=  BIT(4); /* R/W */

> +		data[0] |=  BIT(4);		/* R/W */

> 

> -	data[1] = (msg->address >> 8) & 0xff;	/* addr[15:8] */

> -	data[2] = msg->address & 0xff;		/* addr[7:0] */

> -	data[3] = (msg->size - 1) & 0xff;	/* len[7:0] */

> +	data[1] = msg->address >> 8;		/* addr[15:8] */

> +	data[2] = msg->address;			/* addr[7:0] */

> +	data[3] = msg->size - 1;		/* len[7:0] */

> 

> -	for (i = 0; i < len; i++) {

> +	for (i = 0; i < len + 4; i++) {

>  		reg = (i < 4) ? data[i] : msgdata[i - 4];

> +		reg <<= DP_AUX_DATA_OFFSET;

> +		reg &= DP_AUX_DATA_MASK;

> +		reg |= DP_AUX_DATA_WRITE;

>  		/* index = 0, write */

> -		reg = (((reg) << DP_AUX_DATA_OFFSET)

> -		       & DP_AUX_DATA_MASK) | DP_AUX_DATA_WRITE;

>  		if (i == 0)

>  			reg |= DP_AUX_DATA_INDEX_WRITE;

>  		aux->catalog->aux_data = reg;

> @@ -116,39 +107,27 @@ static u32 dp_aux_write(struct dp_aux_private 

> *aux,

>  	return len;

>  }

> 

> -static int dp_aux_cmd_fifo_tx(struct dp_aux_private *aux,

> +static ssize_t dp_aux_cmd_fifo_tx(struct dp_aux_private *aux,

>  			      struct drm_dp_aux_msg *msg)

>  {

> -	u32 ret, len, timeout;

> -	int aux_timeout_ms = HZ/4;

> +	ssize_t ret;

> +	unsigned long time_left;

> 

>  	reinit_completion(&aux->comp);

> 

> -	len = dp_aux_write(aux, msg);

> -	if (len == 0) {

> -		DRM_ERROR("DP AUX write failed\n");

> -		return -EINVAL;

> -	}

> +	ret = dp_aux_write(aux, msg);

> +	if (ret < 0)

> +		return ret;

> 

> -	timeout = wait_for_completion_timeout(&aux->comp, aux_timeout_ms);

> -	if (!timeout) {

> -		DRM_ERROR("aux %s timeout\n", (aux->read ? "read" : "write"));

> +	time_left = wait_for_completion_timeout(&aux->comp,

> +						msecs_to_jiffies(250));

> +	if (!time_left)

>  		return -ETIMEDOUT;

> -	}

> -

> -	if (aux->aux_error_num == DP_AUX_ERR_NONE) {

> -		ret = len;

> -	} else {

> -		DRM_ERROR_RATELIMITED("aux err: %s\n",

> -			dp_aux_get_error(aux->aux_error_num));

> -

> -		ret = -EINVAL;

> -	}

> 

>  	return ret;

>  }

> 

> -static void dp_aux_cmd_fifo_rx(struct dp_aux_private *aux,

> +static ssize_t dp_aux_cmd_fifo_rx(struct dp_aux_private *aux,

>  		struct drm_dp_aux_msg *msg)

>  {

>  	u32 data;

> @@ -175,9 +154,10 @@ static void dp_aux_cmd_fifo_rx(struct 

> dp_aux_private *aux,

> 

>  		actual_i = (data >> DP_AUX_DATA_INDEX_OFFSET) & 0xFF;

>  		if (i != actual_i)

> -			DRM_ERROR("Index mismatch: expected %d, found %d\n",

> -				i, actual_i);

> +			break;

>  	}

> +

> +	return i;

>  }

> 

>  static void dp_aux_native_handler(struct dp_aux_private *aux, u32 isr)

> @@ -367,36 +347,38 @@ static ssize_t dp_aux_transfer(struct drm_dp_aux 

> *dp_aux,

>  	}

> 

>  	ret = dp_aux_cmd_fifo_tx(aux, msg);

> -

>  	if (ret < 0) {

>  		if (aux->native) {

>  			aux->retry_cnt++;

>  			if (!(aux->retry_cnt % MAX_AUX_RETRIES))

>  				dp_catalog_aux_update_cfg(aux->catalog);

>  		}

> -		usleep_range(400, 500); /* at least 400us to next try */

> -		goto unlock_exit;

> -	}


1) dp_catalog_aux_update_cfg(aux->catalog) will not work without  
dp_catalog_aux_reset(aux->catalog);
dp_catalog_aux_reset(aux->catalog) will reset hpd control block and 
potentially cause pending hpd interrupts got lost.
Therefore I think we should not do 
dp_catalog_aux_update_cfg(aux->catalog) for now.
reset aux controller will reset hpd control block probolem will be fixed 
at next chipset.
after that we can add dp_catalog_aux_update_cfg(aux->catalog) followed 
by dp_catalog_aux_reset(aux->catalog) back at next chipset.

2) according to DP specification, aux read/write failed have to wait at 
least 400us before next try can start.
Otherwise, DP compliant test will failed


> -

> -	if (aux->aux_error_num == DP_AUX_ERR_NONE) {

> -		if (aux->read)

> -			dp_aux_cmd_fifo_rx(aux, msg);

> -

> -		msg->reply = aux->native ?

> -			DP_AUX_NATIVE_REPLY_ACK : DP_AUX_I2C_REPLY_ACK;

>  	} else {

> -		/* Reply defer to retry */

> -		msg->reply = aux->native ?

> -			DP_AUX_NATIVE_REPLY_DEFER : DP_AUX_I2C_REPLY_DEFER;

> +		aux->retry_cnt = 0;

> +		switch (aux->aux_error_num) {

> +		case DP_AUX_ERR_NONE:

> +			if (aux->read)

> +				ret = dp_aux_cmd_fifo_rx(aux, msg);

> +			msg->reply = aux->native ? DP_AUX_NATIVE_REPLY_ACK : 

> DP_AUX_I2C_REPLY_ACK;

> +			break;

> +		case DP_AUX_ERR_DEFER:

> +			msg->reply = aux->native ? DP_AUX_NATIVE_REPLY_DEFER :

> DP_AUX_I2C_REPLY_DEFER;

> +			break;

> +		case DP_AUX_ERR_PHY:

> +		case DP_AUX_ERR_ADDR:

> +		case DP_AUX_ERR_NACK:

> +		case DP_AUX_ERR_NACK_DEFER:

> +			msg->reply = aux->native ? DP_AUX_NATIVE_REPLY_NACK : 

> DP_AUX_I2C_REPLY_NACK;

> +			break;

> +		case DP_AUX_ERR_TOUT:

> +			ret = -ETIMEDOUT;

> +			break;

> +		}

>  	}

> 

> -	/* Return requested size for success or retry */

> -	ret = msg->size;

> -	aux->retry_cnt = 0;

> -

> -unlock_exit:

>  	aux->cmd_busy = false;

>  	mutex_unlock(&aux->mutex);

> +

>  	return ret;

>  }

> 

> diff --git a/drivers/gpu/drm/msm/dp/dp_aux.h 

> b/drivers/gpu/drm/msm/dp/dp_aux.h

> index f8b8ba919465..0728cc09c9ec 100644

> --- a/drivers/gpu/drm/msm/dp/dp_aux.h

> +++ b/drivers/gpu/drm/msm/dp/dp_aux.h

> @@ -9,14 +9,6 @@

>  #include "dp_catalog.h"

>  #include <drm/drm_dp_helper.h>

> 

> -#define DP_AUX_ERR_NONE		0

> -#define DP_AUX_ERR_ADDR		-1

> -#define DP_AUX_ERR_TOUT		-2

> -#define DP_AUX_ERR_NACK		-3

> -#define DP_AUX_ERR_DEFER	-4

> -#define DP_AUX_ERR_NACK_DEFER	-5

> -#define DP_AUX_ERR_PHY		-6

> -

>  int dp_aux_register(struct drm_dp_aux *dp_aux);

>  void dp_aux_unregister(struct drm_dp_aux *dp_aux);

>  void dp_aux_isr(struct drm_dp_aux *dp_aux);
Stephen Boyd May 24, 2021, 7:19 p.m. | #2
Quoting khsieh@codeaurora.org (2021-05-24 09:33:49)
> On 2021-05-07 14:25, Stephen Boyd wrote:
> > @@ -367,36 +347,38 @@ static ssize_t dp_aux_transfer(struct drm_dp_aux
> > *dp_aux,
> >       }
> >
> >       ret = dp_aux_cmd_fifo_tx(aux, msg);
> > -
> >       if (ret < 0) {
> >               if (aux->native) {
> >                       aux->retry_cnt++;
> >                       if (!(aux->retry_cnt % MAX_AUX_RETRIES))
> >                               dp_catalog_aux_update_cfg(aux->catalog);
> >               }
> > -             usleep_range(400, 500); /* at least 400us to next try */
> > -             goto unlock_exit;
> > -     }
>
> 1) dp_catalog_aux_update_cfg(aux->catalog) will not work without
> dp_catalog_aux_reset(aux->catalog);
> dp_catalog_aux_reset(aux->catalog) will reset hpd control block and
> potentially cause pending hpd interrupts got lost.
> Therefore I think we should not do
> dp_catalog_aux_update_cfg(aux->catalog) for now.
> reset aux controller will reset hpd control block probolem will be fixed
> at next chipset.
> after that we can add dp_catalog_aux_update_cfg(aux->catalog) followed
> by dp_catalog_aux_reset(aux->catalog) back at next chipset.

Hmm ok. So the phy calibration logic that tweaks the tuning values is
never used? Why can't the phy be tuned while it is active? I don't
understand why we would ever want to reset the aux phy when changing the
settings for a retry. Either way, this is not actually changing in this
patch so it would be another patch to remove this code.

>
> 2) according to DP specification, aux read/write failed have to wait at
> least 400us before next try can start.
> Otherwise, DP compliant test will failed

Yes. The caller of this function, drm_dp_dpcd_access(), has the delay
already

                if (ret != 0 && ret != -ETIMEDOUT) {
                        usleep_range(AUX_RETRY_INTERVAL,
                                     AUX_RETRY_INTERVAL + 100);
                }

so this delay here is redundant.
Kuogee Hsieh May 24, 2021, 7:57 p.m. | #3
On 2021-05-24 12:19, Stephen Boyd wrote:
> Quoting khsieh@codeaurora.org (2021-05-24 09:33:49)
>> On 2021-05-07 14:25, Stephen Boyd wrote:
>> > @@ -367,36 +347,38 @@ static ssize_t dp_aux_transfer(struct drm_dp_aux
>> > *dp_aux,
>> >       }
>> >
>> >       ret = dp_aux_cmd_fifo_tx(aux, msg);
>> > -
>> >       if (ret < 0) {
>> >               if (aux->native) {
>> >                       aux->retry_cnt++;
>> >                       if (!(aux->retry_cnt % MAX_AUX_RETRIES))
>> >                               dp_catalog_aux_update_cfg(aux->catalog);
>> >               }
>> > -             usleep_range(400, 500); /* at least 400us to next try */
>> > -             goto unlock_exit;
>> > -     }
>> 
>> 1) dp_catalog_aux_update_cfg(aux->catalog) will not work without
>> dp_catalog_aux_reset(aux->catalog);
>> dp_catalog_aux_reset(aux->catalog) will reset hpd control block and
>> potentially cause pending hpd interrupts got lost.
>> Therefore I think we should not do
>> dp_catalog_aux_update_cfg(aux->catalog) for now.
>> reset aux controller will reset hpd control block probolem will be 
>> fixed
>> at next chipset.
>> after that we can add dp_catalog_aux_update_cfg(aux->catalog) followed
>> by dp_catalog_aux_reset(aux->catalog) back at next chipset.
> 
> Hmm ok. So the phy calibration logic that tweaks the tuning values is
> never used? Why can't the phy be tuned while it is active? I don't
> understand why we would ever want to reset the aux phy when changing 
> the
> settings for a retry. Either way, this is not actually changing in this
> patch so it would be another patch to remove this code.
ok,
> 
>> 
>> 2) according to DP specification, aux read/write failed have to wait 
>> at
>> least 400us before next try can start.
>> Otherwise, DP compliant test will failed
> 
> Yes. The caller of this function, drm_dp_dpcd_access(), has the delay
> already
> 
>                 if (ret != 0 && ret != -ETIMEDOUT) {
>                         usleep_range(AUX_RETRY_INTERVAL,
>                                      AUX_RETRY_INTERVAL + 100);
>                 }
> 
> so this delay here is redundant.
yes, you are right. This is enough.
Kuogee Hsieh May 24, 2021, 7:59 p.m. | #4
On 2021-05-07 14:25, Stephen Boyd wrote:
> Let's look at the irq status bits after a transfer and see if we got a

> nack or a defer or a timeout, instead of telling drm layers that

> everything was fine, while still printing an error message. I wasn't

> sure about NACK+DEFER so I lumped all those various errors along with a

> nack so that the drm core can figure out that things are just not going

> well. The important thing is that we're now returning -ETIMEDOUT when

> the message times out and nacks for bad addresses.

> 

> Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

> Cc: Abhinav Kumar <abhinavk@codeaurora.org>

> Cc: Kuogee Hsieh <khsieh@codeaurora.org>

> Cc: aravindh@codeaurora.org

> Cc: Sean Paul <sean@poorly.run>

> Signed-off-by: Stephen Boyd <swboyd@chromium.org>


Reviewed-by: Kuogee Hsieh <khsieh@codeaurora.org>


> ---

>  drivers/gpu/drm/msm/dp/dp_aux.c | 140 ++++++++++++++------------------

>  drivers/gpu/drm/msm/dp/dp_aux.h |   8 --

>  2 files changed, 61 insertions(+), 87 deletions(-)

> 

> diff --git a/drivers/gpu/drm/msm/dp/dp_aux.c 

> b/drivers/gpu/drm/msm/dp/dp_aux.c

> index b49810396513..4a3293b590b0 100644

> --- a/drivers/gpu/drm/msm/dp/dp_aux.c

> +++ b/drivers/gpu/drm/msm/dp/dp_aux.c

> @@ -9,7 +9,15 @@

>  #include "dp_reg.h"

>  #include "dp_aux.h"

> 

> -#define DP_AUX_ENUM_STR(x)		#x

> +enum msm_dp_aux_err {

> +	DP_AUX_ERR_NONE,

> +	DP_AUX_ERR_ADDR,

> +	DP_AUX_ERR_TOUT,

> +	DP_AUX_ERR_NACK,

> +	DP_AUX_ERR_DEFER,

> +	DP_AUX_ERR_NACK_DEFER,

> +	DP_AUX_ERR_PHY,

> +};

> 

>  struct dp_aux_private {

>  	struct device *dev;

> @@ -18,7 +26,7 @@ struct dp_aux_private {

>  	struct mutex mutex;

>  	struct completion comp;

> 

> -	u32 aux_error_num;

> +	enum msm_dp_aux_err aux_error_num;

>  	u32 retry_cnt;

>  	bool cmd_busy;

>  	bool native;

> @@ -33,62 +41,45 @@ struct dp_aux_private {

> 

>  #define MAX_AUX_RETRIES			5

> 

> -static const char *dp_aux_get_error(u32 aux_error)

> -{

> -	switch (aux_error) {

> -	case DP_AUX_ERR_NONE:

> -		return DP_AUX_ENUM_STR(DP_AUX_ERR_NONE);

> -	case DP_AUX_ERR_ADDR:

> -		return DP_AUX_ENUM_STR(DP_AUX_ERR_ADDR);

> -	case DP_AUX_ERR_TOUT:

> -		return DP_AUX_ENUM_STR(DP_AUX_ERR_TOUT);

> -	case DP_AUX_ERR_NACK:

> -		return DP_AUX_ENUM_STR(DP_AUX_ERR_NACK);

> -	case DP_AUX_ERR_DEFER:

> -		return DP_AUX_ENUM_STR(DP_AUX_ERR_DEFER);

> -	case DP_AUX_ERR_NACK_DEFER:

> -		return DP_AUX_ENUM_STR(DP_AUX_ERR_NACK_DEFER);

> -	default:

> -		return "unknown";

> -	}

> -}

> -

> -static u32 dp_aux_write(struct dp_aux_private *aux,

> +static ssize_t dp_aux_write(struct dp_aux_private *aux,

>  			struct drm_dp_aux_msg *msg)

>  {

> -	u32 data[4], reg, len;

> +	u8 data[4];

> +	u32 reg;

> +	ssize_t len;

>  	u8 *msgdata = msg->buffer;

>  	int const AUX_CMD_FIFO_LEN = 128;

>  	int i = 0;

> 

>  	if (aux->read)

> -		len = 4;

> +		len = 0;

>  	else

> -		len = msg->size + 4;

> +		len = msg->size;

> 

>  	/*

>  	 * cmd fifo only has depth of 144 bytes

>  	 * limit buf length to 128 bytes here

>  	 */

> -	if (len > AUX_CMD_FIFO_LEN) {

> +	if (len > AUX_CMD_FIFO_LEN - 4) {

>  		DRM_ERROR("buf size greater than allowed size of 128 bytes\n");

> -		return 0;

> +		return -EINVAL;

>  	}

> 

>  	/* Pack cmd and write to HW */

> -	data[0] = (msg->address >> 16) & 0xf; /* addr[19:16] */

> +	data[0] = (msg->address >> 16) & 0xf;	/* addr[19:16] */

>  	if (aux->read)

> -		data[0] |=  BIT(4); /* R/W */

> +		data[0] |=  BIT(4);		/* R/W */

> 

> -	data[1] = (msg->address >> 8) & 0xff;	/* addr[15:8] */

> -	data[2] = msg->address & 0xff;		/* addr[7:0] */

> -	data[3] = (msg->size - 1) & 0xff;	/* len[7:0] */

> +	data[1] = msg->address >> 8;		/* addr[15:8] */

> +	data[2] = msg->address;			/* addr[7:0] */

> +	data[3] = msg->size - 1;		/* len[7:0] */

> 

> -	for (i = 0; i < len; i++) {

> +	for (i = 0; i < len + 4; i++) {

>  		reg = (i < 4) ? data[i] : msgdata[i - 4];

> +		reg <<= DP_AUX_DATA_OFFSET;

> +		reg &= DP_AUX_DATA_MASK;

> +		reg |= DP_AUX_DATA_WRITE;

>  		/* index = 0, write */

> -		reg = (((reg) << DP_AUX_DATA_OFFSET)

> -		       & DP_AUX_DATA_MASK) | DP_AUX_DATA_WRITE;

>  		if (i == 0)

>  			reg |= DP_AUX_DATA_INDEX_WRITE;

>  		aux->catalog->aux_data = reg;

> @@ -116,39 +107,27 @@ static u32 dp_aux_write(struct dp_aux_private 

> *aux,

>  	return len;

>  }

> 

> -static int dp_aux_cmd_fifo_tx(struct dp_aux_private *aux,

> +static ssize_t dp_aux_cmd_fifo_tx(struct dp_aux_private *aux,

>  			      struct drm_dp_aux_msg *msg)

>  {

> -	u32 ret, len, timeout;

> -	int aux_timeout_ms = HZ/4;

> +	ssize_t ret;

> +	unsigned long time_left;

> 

>  	reinit_completion(&aux->comp);

> 

> -	len = dp_aux_write(aux, msg);

> -	if (len == 0) {

> -		DRM_ERROR("DP AUX write failed\n");

> -		return -EINVAL;

> -	}

> +	ret = dp_aux_write(aux, msg);

> +	if (ret < 0)

> +		return ret;

> 

> -	timeout = wait_for_completion_timeout(&aux->comp, aux_timeout_ms);

> -	if (!timeout) {

> -		DRM_ERROR("aux %s timeout\n", (aux->read ? "read" : "write"));

> +	time_left = wait_for_completion_timeout(&aux->comp,

> +						msecs_to_jiffies(250));

> +	if (!time_left)

>  		return -ETIMEDOUT;

> -	}

> -

> -	if (aux->aux_error_num == DP_AUX_ERR_NONE) {

> -		ret = len;

> -	} else {

> -		DRM_ERROR_RATELIMITED("aux err: %s\n",

> -			dp_aux_get_error(aux->aux_error_num));

> -

> -		ret = -EINVAL;

> -	}

> 

>  	return ret;

>  }

> 

> -static void dp_aux_cmd_fifo_rx(struct dp_aux_private *aux,

> +static ssize_t dp_aux_cmd_fifo_rx(struct dp_aux_private *aux,

>  		struct drm_dp_aux_msg *msg)

>  {

>  	u32 data;

> @@ -175,9 +154,10 @@ static void dp_aux_cmd_fifo_rx(struct 

> dp_aux_private *aux,

> 

>  		actual_i = (data >> DP_AUX_DATA_INDEX_OFFSET) & 0xFF;

>  		if (i != actual_i)

> -			DRM_ERROR("Index mismatch: expected %d, found %d\n",

> -				i, actual_i);

> +			break;

>  	}

> +

> +	return i;

>  }

> 

>  static void dp_aux_native_handler(struct dp_aux_private *aux, u32 isr)

> @@ -367,36 +347,38 @@ static ssize_t dp_aux_transfer(struct drm_dp_aux 

> *dp_aux,

>  	}

> 

>  	ret = dp_aux_cmd_fifo_tx(aux, msg);

> -

>  	if (ret < 0) {

>  		if (aux->native) {

>  			aux->retry_cnt++;

>  			if (!(aux->retry_cnt % MAX_AUX_RETRIES))

>  				dp_catalog_aux_update_cfg(aux->catalog);

>  		}

> -		usleep_range(400, 500); /* at least 400us to next try */

> -		goto unlock_exit;

> -	}

> -

> -	if (aux->aux_error_num == DP_AUX_ERR_NONE) {

> -		if (aux->read)

> -			dp_aux_cmd_fifo_rx(aux, msg);

> -

> -		msg->reply = aux->native ?

> -			DP_AUX_NATIVE_REPLY_ACK : DP_AUX_I2C_REPLY_ACK;

>  	} else {

> -		/* Reply defer to retry */

> -		msg->reply = aux->native ?

> -			DP_AUX_NATIVE_REPLY_DEFER : DP_AUX_I2C_REPLY_DEFER;

> +		aux->retry_cnt = 0;

> +		switch (aux->aux_error_num) {

> +		case DP_AUX_ERR_NONE:

> +			if (aux->read)

> +				ret = dp_aux_cmd_fifo_rx(aux, msg);

> +			msg->reply = aux->native ? DP_AUX_NATIVE_REPLY_ACK : 

> DP_AUX_I2C_REPLY_ACK;

> +			break;

> +		case DP_AUX_ERR_DEFER:

> +			msg->reply = aux->native ? DP_AUX_NATIVE_REPLY_DEFER :

> DP_AUX_I2C_REPLY_DEFER;

> +			break;

> +		case DP_AUX_ERR_PHY:

> +		case DP_AUX_ERR_ADDR:

> +		case DP_AUX_ERR_NACK:

> +		case DP_AUX_ERR_NACK_DEFER:

> +			msg->reply = aux->native ? DP_AUX_NATIVE_REPLY_NACK : 

> DP_AUX_I2C_REPLY_NACK;

> +			break;

> +		case DP_AUX_ERR_TOUT:

> +			ret = -ETIMEDOUT;

> +			break;

> +		}

>  	}

> 

> -	/* Return requested size for success or retry */

> -	ret = msg->size;

> -	aux->retry_cnt = 0;

> -

> -unlock_exit:

>  	aux->cmd_busy = false;

>  	mutex_unlock(&aux->mutex);

> +

>  	return ret;

>  }

> 

> diff --git a/drivers/gpu/drm/msm/dp/dp_aux.h 

> b/drivers/gpu/drm/msm/dp/dp_aux.h

> index f8b8ba919465..0728cc09c9ec 100644

> --- a/drivers/gpu/drm/msm/dp/dp_aux.h

> +++ b/drivers/gpu/drm/msm/dp/dp_aux.h

> @@ -9,14 +9,6 @@

>  #include "dp_catalog.h"

>  #include <drm/drm_dp_helper.h>

> 

> -#define DP_AUX_ERR_NONE		0

> -#define DP_AUX_ERR_ADDR		-1

> -#define DP_AUX_ERR_TOUT		-2

> -#define DP_AUX_ERR_NACK		-3

> -#define DP_AUX_ERR_DEFER	-4

> -#define DP_AUX_ERR_NACK_DEFER	-5

> -#define DP_AUX_ERR_PHY		-6

> -

>  int dp_aux_register(struct drm_dp_aux *dp_aux);

>  void dp_aux_unregister(struct drm_dp_aux *dp_aux);

>  void dp_aux_isr(struct drm_dp_aux *dp_aux);

Patch

diff --git a/drivers/gpu/drm/msm/dp/dp_aux.c b/drivers/gpu/drm/msm/dp/dp_aux.c
index b49810396513..4a3293b590b0 100644
--- a/drivers/gpu/drm/msm/dp/dp_aux.c
+++ b/drivers/gpu/drm/msm/dp/dp_aux.c
@@ -9,7 +9,15 @@ 
 #include "dp_reg.h"
 #include "dp_aux.h"
 
-#define DP_AUX_ENUM_STR(x)		#x
+enum msm_dp_aux_err {
+	DP_AUX_ERR_NONE,
+	DP_AUX_ERR_ADDR,
+	DP_AUX_ERR_TOUT,
+	DP_AUX_ERR_NACK,
+	DP_AUX_ERR_DEFER,
+	DP_AUX_ERR_NACK_DEFER,
+	DP_AUX_ERR_PHY,
+};
 
 struct dp_aux_private {
 	struct device *dev;
@@ -18,7 +26,7 @@  struct dp_aux_private {
 	struct mutex mutex;
 	struct completion comp;
 
-	u32 aux_error_num;
+	enum msm_dp_aux_err aux_error_num;
 	u32 retry_cnt;
 	bool cmd_busy;
 	bool native;
@@ -33,62 +41,45 @@  struct dp_aux_private {
 
 #define MAX_AUX_RETRIES			5
 
-static const char *dp_aux_get_error(u32 aux_error)
-{
-	switch (aux_error) {
-	case DP_AUX_ERR_NONE:
-		return DP_AUX_ENUM_STR(DP_AUX_ERR_NONE);
-	case DP_AUX_ERR_ADDR:
-		return DP_AUX_ENUM_STR(DP_AUX_ERR_ADDR);
-	case DP_AUX_ERR_TOUT:
-		return DP_AUX_ENUM_STR(DP_AUX_ERR_TOUT);
-	case DP_AUX_ERR_NACK:
-		return DP_AUX_ENUM_STR(DP_AUX_ERR_NACK);
-	case DP_AUX_ERR_DEFER:
-		return DP_AUX_ENUM_STR(DP_AUX_ERR_DEFER);
-	case DP_AUX_ERR_NACK_DEFER:
-		return DP_AUX_ENUM_STR(DP_AUX_ERR_NACK_DEFER);
-	default:
-		return "unknown";
-	}
-}
-
-static u32 dp_aux_write(struct dp_aux_private *aux,
+static ssize_t dp_aux_write(struct dp_aux_private *aux,
 			struct drm_dp_aux_msg *msg)
 {
-	u32 data[4], reg, len;
+	u8 data[4];
+	u32 reg;
+	ssize_t len;
 	u8 *msgdata = msg->buffer;
 	int const AUX_CMD_FIFO_LEN = 128;
 	int i = 0;
 
 	if (aux->read)
-		len = 4;
+		len = 0;
 	else
-		len = msg->size + 4;
+		len = msg->size;
 
 	/*
 	 * cmd fifo only has depth of 144 bytes
 	 * limit buf length to 128 bytes here
 	 */
-	if (len > AUX_CMD_FIFO_LEN) {
+	if (len > AUX_CMD_FIFO_LEN - 4) {
 		DRM_ERROR("buf size greater than allowed size of 128 bytes\n");
-		return 0;
+		return -EINVAL;
 	}
 
 	/* Pack cmd and write to HW */
-	data[0] = (msg->address >> 16) & 0xf; /* addr[19:16] */
+	data[0] = (msg->address >> 16) & 0xf;	/* addr[19:16] */
 	if (aux->read)
-		data[0] |=  BIT(4); /* R/W */
+		data[0] |=  BIT(4);		/* R/W */
 
-	data[1] = (msg->address >> 8) & 0xff;	/* addr[15:8] */
-	data[2] = msg->address & 0xff;		/* addr[7:0] */
-	data[3] = (msg->size - 1) & 0xff;	/* len[7:0] */
+	data[1] = msg->address >> 8;		/* addr[15:8] */
+	data[2] = msg->address;			/* addr[7:0] */
+	data[3] = msg->size - 1;		/* len[7:0] */
 
-	for (i = 0; i < len; i++) {
+	for (i = 0; i < len + 4; i++) {
 		reg = (i < 4) ? data[i] : msgdata[i - 4];
+		reg <<= DP_AUX_DATA_OFFSET;
+		reg &= DP_AUX_DATA_MASK;
+		reg |= DP_AUX_DATA_WRITE;
 		/* index = 0, write */
-		reg = (((reg) << DP_AUX_DATA_OFFSET)
-		       & DP_AUX_DATA_MASK) | DP_AUX_DATA_WRITE;
 		if (i == 0)
 			reg |= DP_AUX_DATA_INDEX_WRITE;
 		aux->catalog->aux_data = reg;
@@ -116,39 +107,27 @@  static u32 dp_aux_write(struct dp_aux_private *aux,
 	return len;
 }
 
-static int dp_aux_cmd_fifo_tx(struct dp_aux_private *aux,
+static ssize_t dp_aux_cmd_fifo_tx(struct dp_aux_private *aux,
 			      struct drm_dp_aux_msg *msg)
 {
-	u32 ret, len, timeout;
-	int aux_timeout_ms = HZ/4;
+	ssize_t ret;
+	unsigned long time_left;
 
 	reinit_completion(&aux->comp);
 
-	len = dp_aux_write(aux, msg);
-	if (len == 0) {
-		DRM_ERROR("DP AUX write failed\n");
-		return -EINVAL;
-	}
+	ret = dp_aux_write(aux, msg);
+	if (ret < 0)
+		return ret;
 
-	timeout = wait_for_completion_timeout(&aux->comp, aux_timeout_ms);
-	if (!timeout) {
-		DRM_ERROR("aux %s timeout\n", (aux->read ? "read" : "write"));
+	time_left = wait_for_completion_timeout(&aux->comp,
+						msecs_to_jiffies(250));
+	if (!time_left)
 		return -ETIMEDOUT;
-	}
-
-	if (aux->aux_error_num == DP_AUX_ERR_NONE) {
-		ret = len;
-	} else {
-		DRM_ERROR_RATELIMITED("aux err: %s\n",
-			dp_aux_get_error(aux->aux_error_num));
-
-		ret = -EINVAL;
-	}
 
 	return ret;
 }
 
-static void dp_aux_cmd_fifo_rx(struct dp_aux_private *aux,
+static ssize_t dp_aux_cmd_fifo_rx(struct dp_aux_private *aux,
 		struct drm_dp_aux_msg *msg)
 {
 	u32 data;
@@ -175,9 +154,10 @@  static void dp_aux_cmd_fifo_rx(struct dp_aux_private *aux,
 
 		actual_i = (data >> DP_AUX_DATA_INDEX_OFFSET) & 0xFF;
 		if (i != actual_i)
-			DRM_ERROR("Index mismatch: expected %d, found %d\n",
-				i, actual_i);
+			break;
 	}
+
+	return i;
 }
 
 static void dp_aux_native_handler(struct dp_aux_private *aux, u32 isr)
@@ -367,36 +347,38 @@  static ssize_t dp_aux_transfer(struct drm_dp_aux *dp_aux,
 	}
 
 	ret = dp_aux_cmd_fifo_tx(aux, msg);
-
 	if (ret < 0) {
 		if (aux->native) {
 			aux->retry_cnt++;
 			if (!(aux->retry_cnt % MAX_AUX_RETRIES))
 				dp_catalog_aux_update_cfg(aux->catalog);
 		}
-		usleep_range(400, 500); /* at least 400us to next try */
-		goto unlock_exit;
-	}
-
-	if (aux->aux_error_num == DP_AUX_ERR_NONE) {
-		if (aux->read)
-			dp_aux_cmd_fifo_rx(aux, msg);
-
-		msg->reply = aux->native ?
-			DP_AUX_NATIVE_REPLY_ACK : DP_AUX_I2C_REPLY_ACK;
 	} else {
-		/* Reply defer to retry */
-		msg->reply = aux->native ?
-			DP_AUX_NATIVE_REPLY_DEFER : DP_AUX_I2C_REPLY_DEFER;
+		aux->retry_cnt = 0;
+		switch (aux->aux_error_num) {
+		case DP_AUX_ERR_NONE:
+			if (aux->read)
+				ret = dp_aux_cmd_fifo_rx(aux, msg);
+			msg->reply = aux->native ? DP_AUX_NATIVE_REPLY_ACK : DP_AUX_I2C_REPLY_ACK;
+			break;
+		case DP_AUX_ERR_DEFER:
+			msg->reply = aux->native ? DP_AUX_NATIVE_REPLY_DEFER : DP_AUX_I2C_REPLY_DEFER;
+			break;
+		case DP_AUX_ERR_PHY:
+		case DP_AUX_ERR_ADDR:
+		case DP_AUX_ERR_NACK:
+		case DP_AUX_ERR_NACK_DEFER:
+			msg->reply = aux->native ? DP_AUX_NATIVE_REPLY_NACK : DP_AUX_I2C_REPLY_NACK;
+			break;
+		case DP_AUX_ERR_TOUT:
+			ret = -ETIMEDOUT;
+			break;
+		}
 	}
 
-	/* Return requested size for success or retry */
-	ret = msg->size;
-	aux->retry_cnt = 0;
-
-unlock_exit:
 	aux->cmd_busy = false;
 	mutex_unlock(&aux->mutex);
+
 	return ret;
 }
 
diff --git a/drivers/gpu/drm/msm/dp/dp_aux.h b/drivers/gpu/drm/msm/dp/dp_aux.h
index f8b8ba919465..0728cc09c9ec 100644
--- a/drivers/gpu/drm/msm/dp/dp_aux.h
+++ b/drivers/gpu/drm/msm/dp/dp_aux.h
@@ -9,14 +9,6 @@ 
 #include "dp_catalog.h"
 #include <drm/drm_dp_helper.h>
 
-#define DP_AUX_ERR_NONE		0
-#define DP_AUX_ERR_ADDR		-1
-#define DP_AUX_ERR_TOUT		-2
-#define DP_AUX_ERR_NACK		-3
-#define DP_AUX_ERR_DEFER	-4
-#define DP_AUX_ERR_NACK_DEFER	-5
-#define DP_AUX_ERR_PHY		-6
-
 int dp_aux_register(struct drm_dp_aux *dp_aux);
 void dp_aux_unregister(struct drm_dp_aux *dp_aux);
 void dp_aux_isr(struct drm_dp_aux *dp_aux);