Re: [PATCH v2 13/18] DRM/KMS/EDID: Cache EDID blobs with extensions (v2)

On Thu, Nov 22, 2012 at 05:23:03AM -0500, Egbert Eich wrote:

According the the VESA specs there can be up to 254 EEDID extension blocks. Since we may read the EDID (including extensions) in 10 second intervals to probe for display hotplugging (at least in cases where no hardware hotplug detection exists) and I2C transfer is rather slow we may end up consuming a considerable amount on CPU time for just that. This patch caches the EDID block if it contains at least one extension. To determine if the blocks match we only tranfer the base block, on a match we use the cached data.

V2: Use kmemdup() instead of a kmalloc()/memcpy() combo, erase cache when reading a 'firmware'-supplied EDID or on error.

Signed-off-by: Egbert Eich eich@suse.com

drivers/gpu/drm/drm_crtc.c | 1 + drivers/gpu/drm/drm_edid.c | 57 +++++++++++++++++++++++++++++++++++++------ include/drm/drm_crtc.h | 1 + include/drm/drm_edid.h | 1 + 4 files changed, 52 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c index 3533609..e283355 100644 --- a/drivers/gpu/drm/drm_crtc.c +++ b/drivers/gpu/drm/drm_crtc.c @@ -598,6 +598,7 @@ void drm_connector_cleanup(struct drm_connector *connector) drm_mode_remove(connector, mode);

mutex_lock(&dev->mode_config.mutex);

• drm_cache_edid(connector, NULL); drm_mode_object_put(dev, &connector->base); list_del(&connector->head); dev->mode_config.num_connector--;

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c index a47fa7f..28b877c 100644 --- a/drivers/gpu/drm/drm_edid.c +++ b/drivers/gpu/drm/drm_edid.c @@ -419,6 +419,38 @@ fixup_edid(u8 **blockp, int valid_extensions) } }

+static bool +compare_get_edid_from_cache(struct drm_connector *connector, struct edid **edidp) +{

• if (connector->edid_cache &&

•    connector->edid_cache->prod_code[0] == (*edidp)->prod_code[0] &&
  

•    connector->edid_cache->prod_code[1] == (*edidp)->prod_code[1] &&
  

•    connector->edid_cache->serial == (*edidp)->serial &&
  

•    connector->edid_cache->input == (*edidp)->input) {
  

• int size = (connector->edid_cache->extensions + 1) * EDID_LENGTH;
  

• struct edid *new = kmemdup(connector->edid_cache, size, GFP_KERNEL);
  

• if (!new)
  

• 	return false;
  

• DRM_DEBUG_KMS("Got EDID for %s from cache.\n", drm_get_connector_name(connector));
  

• kfree(*edidp);
  

• *edidp = new;
  

• return true;
  

• }
• return false;

+}

+void +drm_cache_edid(struct drm_connector *connector, struct edid *edid) +{

• struct edid *new = NULL;
• kfree(connector->edid_cache);
• if (edid) {

• int size = (edid->extensions + 1) * EDID_LENGTH;
  

• new = kmemdup(edid, size, GFP_KERNEL);
  

• }
• connector->edid_cache = new;

+}

static u8 * drm_do_get_edid(struct drm_connector *connector, struct i2c_adapter *adapter) { @@ -429,28 +461,30 @@ drm_do_get_edid(struct drm_connector *connector, struct i2c_adapter *adapter) #ifdef CONFIG_DRM_LOAD_EDID_FIRMWARE /* check if the user has specified a 'firmware' EDID file */ block = (u8 *)drm_load_edid_firmware(connector);

• if (block)

• if (block) {

• drm_cache_edid(connector, NULL);
  

  return block;
• }

#endif

if ((block = kmalloc(EDID_LENGTH, GFP_KERNEL)) == NULL)

• return NULL;
  

• goto error;
  
  

  /* base block fetch */ for (i = 0; i < 4; i++) { if (drm_do_probe_ddc_edid(adapter, block, 0, EDID_LENGTH))

• 	goto out;
  

• 	goto error_free;
  

  if (drm_edid_block_valid(block, 0, print_bad_edid)) break; if (i == 0 && drm_edid_is_zero(block, EDID_LENGTH)) { connector->null_edid_counter++;

• 	goto carp;
  

• 	goto error_carp;
  

  } } if (i == 4)

• goto carp;
  

• goto error_carp;
  
  

• /* if there's no extensions, we're done */

• /* if there are no extensions, we're done - don't bother caching */ if (block[EDID_EXTENSION_FLAG_OFFSET] == 0) return block;

Shouldn't you erase the cache here too?