Re: [PATCH] drm/dp: add DPCD logging

On Tue, 13 Oct 2015, Rob Clark robdclark@gmail.com wrote:

On Tue, Oct 13, 2015 at 10:30 AM, Jani Nikula jani.nikula@linux.intel.com wrote:

...

On Tue, 13 Oct 2015, Rob Clark robdclark@gmail.com wrote:

...

Add a new drm_debug bit for turning on DPCD logging, to aid debugging with troublesome monitors.

I wish you could find some balance between having the error cases logged with normal kms debugging vs. having to have full blown aux traffic debugging to notice everything failed...

At the very least the "too many retries, giving up" should be included in KMS debugging, maybe more.

maybe that should be DRM_ERROR()? Not sure..

I'd be fine with that, especially if you can beat some sense into all the confusion between doing an error and debug logging.

For added complexity, there's some DRM_ERRORs and DRM_DEBUG_KMSs hidden in the ->transfer functions too. See e.g. intel_dp_aux_ch() that gets called by our ->transfer function intel_dp_aux_transfer(), both in i915/intel_dp.c...

BR, Jani.

For what I was debugging I actually wanted to be able to turn on just the DPCD logging without having to turn on all the KMS debugging.. but I can understand the inverse..

BR, -R

...

BR, Jani.

...

Signed-off-by: Rob Clark robdclark@gmail.com

drivers/gpu/drm/drm_dp_helper.c | 66 ++++++++++++++++++++++++++++++++--------- include/drm/drmP.h | 6 ++++ 2 files changed, 58 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 291734e..8e17f55 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -159,6 +159,46 @@ int drm_dp_bw_code_to_link_rate(u8 link_bw) } EXPORT_SYMBOL(drm_dp_bw_code_to_link_rate);

+static ssize_t aux_transfer(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) +{

• size_t ret;
  

• mutex_lock(&aux->hw_mutex);
  

• DRM_DEBUG_DPCD("%s: req=0x%02x, address=0x%05x, size=%zu\n", aux->name,
  

•                 msg->request, msg->address, msg->size);
  

• if (unlikely(drm_debug & DRM_UT_DPCD)) {
  

•         switch (msg->request & ~DP_AUX_I2C_MOT) {
  

•         case DP_AUX_NATIVE_WRITE:
  

•         case DP_AUX_I2C_WRITE:
  

•                 print_hex_dump(KERN_DEBUG, "DPCD: ", DUMP_PREFIX_OFFSET,
  

•                                 16, 1, msg->buffer, msg->size, false);
  

•                 break;
  

•         default:
  

•                 break;
  

•         }
  

• }
  

• ret = aux->transfer(aux, msg);
  

• DRM_DEBUG_DPCD("%s: reply=0x%02x, size=%zu\n", aux->name, msg->reply, ret);
  

• if (unlikely(drm_debug & DRM_UT_DPCD)) {
  

•         switch (msg->request & ~DP_AUX_I2C_MOT) {
  

•         case DP_AUX_NATIVE_READ:
  

•         case DP_AUX_I2C_READ:
  

•                 print_hex_dump(KERN_DEBUG, "DPCD: ", DUMP_PREFIX_OFFSET,
  

•                                 16, 1, msg->buffer, ret, false);
  

•                 break;
  

•         default:
  

•                 break;
  

•         }
  

• }
  

• mutex_unlock(&aux->hw_mutex);
  

• return ret;
  

+}

#define AUX_RETRY_INTERVAL 500 /* us */

/** @@ -194,9 +234,7 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request, */ for (retry = 0; retry < 32; retry++) {

•         mutex_lock(&aux->hw_mutex);
  

•         err = aux->transfer(aux, &msg);
  

•         mutex_unlock(&aux->hw_mutex);
  

•         err = aux_transfer(aux, &msg);
          if (err < 0) {
                  if (err == -EBUSY)
                          continue;
  

@@ -212,15 +250,17 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request, return err;

          case DP_AUX_NATIVE_REPLY_NACK:

•                 DRM_DEBUG_DPCD("native nack (result=%d, size=%zu)\n", err, msg.size);
                  return -EIO;
  
          case DP_AUX_NATIVE_REPLY_DEFER:
  

•                 DRM_DEBUG_DPCD("native defer\n");
                  usleep_range(AUX_RETRY_INTERVAL, AUX_RETRY_INTERVAL + 100);
                  break;
          }
  }
  
  

• DRM_DEBUG_KMS("too many retries, giving up\n");
  

• DRM_DEBUG_DPCD("too many retries, giving up\n");
  return -EIO;
  

}

@@ -530,14 +570,12 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) int max_retries = max(7, drm_dp_i2c_retry_count(msg, dp_aux_i2c_speed_khz));

  for (retry = 0, defer_i2c = 0; retry < (max_retries + defer_i2c); retry++) {

•         mutex_lock(&aux->hw_mutex);
  

•         ret = aux->transfer(aux, msg);
  

•         mutex_unlock(&aux->hw_mutex);
  

•         ret = aux_transfer(aux, msg);
          if (ret < 0) {
                  if (ret == -EBUSY)
                          continue;
  
  

•                 DRM_DEBUG_KMS("transaction failed: %d\n", ret);
  

•                 DRM_DEBUG_DPCD("transaction failed: %d\n", ret);
                  return ret;
          }
  
  

@@ -551,11 +589,11 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) break;

          case DP_AUX_NATIVE_REPLY_NACK:

•                 DRM_DEBUG_KMS("native nack (result=%d, size=%zu)\n", ret, msg->size);
  

•                 DRM_DEBUG_DPCD("native nack (result=%d, size=%zu)\n", ret, msg->size);
                  return -EREMOTEIO;
  
          case DP_AUX_NATIVE_REPLY_DEFER:
  

•                 DRM_DEBUG_KMS("native defer\n");
  

•                 DRM_DEBUG_DPCD("native defer\n");
                  /*
                   * We could check for I2C bit rate capabilities and if
                   * available adjust this interval. We could also be
  

@@ -582,12 +620,12 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) return ret;

          case DP_AUX_I2C_REPLY_NACK:

•                 DRM_DEBUG_KMS("I2C nack (result=%d, size=%zu\n", ret, msg->size);
  

•                 DRM_DEBUG_DPCD("I2C nack (result=%d, size=%zu\n", ret, msg->size);
                  aux->i2c_nack_count++;
                  return -EREMOTEIO;
  
          case DP_AUX_I2C_REPLY_DEFER:
  

•                 DRM_DEBUG_KMS("I2C defer\n");
  

•                 DRM_DEBUG_DPCD("I2C defer\n");
                  /* DP Compliance Test 4.2.2.5 Requirement:
                   * Must have at least 7 retries for I2C defers on the
                   * transaction to pass this test
  

@@ -604,7 +642,7 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) } }

• DRM_DEBUG_KMS("too many retries, giving up\n");
  

• DRM_DEBUG_DPCD("too many retries, giving up\n");
  return -EREMOTEIO;
  

}

@@ -624,7 +662,7 @@ static int drm_dp_i2c_drain_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *o return err == 0 ? -EPROTO : err;

          if (err < msg.size && err < ret) {

•                 DRM_DEBUG_KMS("Partial I2C reply: requested %zu bytes got %d bytes\n",
  

•                 DRM_DEBUG_DPCD("Partial I2C reply: requested %zu bytes got %d bytes\n",
                                msg.size, err);
                  ret = err;
          }
  

diff --git a/include/drm/drmP.h b/include/drm/drmP.h index 8b5ce7c..f6c25cc 100644 --- a/include/drm/drmP.h +++ b/include/drm/drmP.h @@ -125,6 +125,7 @@ struct dma_buf_attachment; #define DRM_UT_KMS 0x04 #define DRM_UT_PRIME 0x08 #define DRM_UT_ATOMIC 0x10 +#define DRM_UT_DPCD 0x20

extern __printf(2, 3) void drm_ut_debug_printk(const char *function_name, @@ -217,6 +218,11 @@ void drm_err(const char *format, ...); if (unlikely(drm_debug & DRM_UT_ATOMIC)) \ drm_ut_debug_printk(__func__, fmt, ##args); \ } while (0) +#define DRM_DEBUG_DPCD(fmt, args...) \

• do {                                                            \
  

•         if (unlikely(drm_debug & DRM_UT_DPCD))                  \
  

•                 drm_ut_debug_printk(__func__, fmt, ##args);     \
  

• } while (0)
  
  

/*@}*/

-- 2.1.0

---

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-- Jani Nikula, Intel Open Source Technology Center