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@xxxxxxxx>
> ---
> 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?
--
Ville Syrjälä
Intel OTC
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