[PATCH 06/13] drm: Add supporting structure for Displayport Link CTS test 4.2.2.6
Todd Previte
tprevite at gmail.com
Tue Apr 14 23:56:25 PDT 2015
On 4/13/15 3:18 PM, Paulo Zanoni wrote:
> 2015-04-13 11:53 GMT-03:00 Todd Previte <tprevite at gmail.com>:
>> Displayport compliance test 4.2.2.6 requires that a source device be capable of
>> detecting a corrupt EDID. The test specification states that the sink device
>> sets up the EDID with an invalid checksum. To do this, the sink sets up an
>> invalid EDID header, expecting the source device to generate the checksum and
>> compare it to the value stored in the last byte of the block data.
>>
>> Unfortunately, the DRM EDID reading and parsing functions are actually too good
>> in this case; the header is fixed before the checksum is computed and thus the
>> code never sees the invalid checksum. This results in a failure to pass the
>> compliance test.
>>
>> To correct this issue, a checksum is generated when the EDID header is detected
>> as corrupted. If the checksum is invalid, it sets the header_corrupt flag and
>> logs the errors. In the case of a more seriously damaged header (fixup score
>> less than the threshold) the code does not generate the checksum but does set
>> the header_corrupt flag.
>>
>> V2:
>> - Removed the static bool global
>> - Added a bool to the drm_connector struct to reaplce the static one for
>> holding the status of raw edid header corruption detection
>> - Modified the function signature of the is_valid function to take an
>> additional parameter to store the corruption detected value
>> - Fixed the other callers of the above is_valid function
>> V3:
>> - Updated the commit message to be more clear about what and why this
>> patch does what it does.
>> - Added comment in code to clarify the operations there
>> - Removed compliance variable and check_link_status update; those
>> have been moved to a later patch
>> - Removed variable assignment from the bottom of the test handler
>> V4:
>> - Removed i915 tag from subject line as the patch is not i915-specific
>> V5:
>> - Moved code causing a compilation error to this patch where the variable
>> is actually declared
>>
>> Signed-off-by: Todd Previte <tprevite at gmail.com>
>> Cc: dri-devel at lists.freedesktop.org
>> ---
>> drivers/gpu/drm/drm_edid.c | 31 ++++++++++++++++++++++++++-----
>> drivers/gpu/drm/drm_edid_load.c | 7 +++++--
>> drivers/gpu/drm/i2c/tda998x_drv.c | 4 ++--
>> drivers/gpu/drm/i915/intel_dp.c | 2 +-
>> include/drm/drm_crtc.h | 8 +++++++-
>> 5 files changed, 41 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
>> index 53bc7a6..12e5be7 100644
>> --- a/drivers/gpu/drm/drm_edid.c
>> +++ b/drivers/gpu/drm/drm_edid.c
>> @@ -1005,7 +1005,6 @@ int drm_edid_header_is_valid(const u8 *raw_edid)
>> for (i = 0; i < sizeof(edid_header); i++)
>> if (raw_edid[i] == edid_header[i])
>> score++;
>> -
>> return score;
>> }
>> EXPORT_SYMBOL(drm_edid_header_is_valid);
> Bad chunk...
Fixed
>
>> @@ -1047,7 +1046,8 @@ static bool drm_edid_is_zero(const u8 *in_edid, int length)
>> *
>> * Return: True if the block is valid, false otherwise.
>> */
>> -bool drm_edid_block_valid(u8 *raw_edid, int block, bool print_bad_edid)
>> +bool drm_edid_block_valid(u8 *raw_edid, int block, bool print_bad_edid,
>> + bool *header_corrupt)
> Need to add the new parameter description to the documentation above.
Done.
>
>> {
>> u8 csum;
>> struct edid *edid = (struct edid *)raw_edid;
>> @@ -1062,9 +1062,27 @@ bool drm_edid_block_valid(u8 *raw_edid, int block, bool print_bad_edid)
>> int score = drm_edid_header_is_valid(raw_edid);
>> if (score == 8) ;
>> else if (score >= edid_fixup) {
>> + /* Displayport Link CTS Core 1.2 rev1.1 test 4.2.2.6
>> + * In order to properly generate the invalid checksum
>> + * required for this test, it must be generated using
>> + * the raw EDID data. Otherwise, the fix-up code here
>> + * will correct the problem, the checksum is then correct
>> + * and the test fails
>> + */
>> + csum = drm_edid_block_checksum(raw_edid);
>> + if (csum) {
>> + DRM_DEBUG_DRIVER("Invalid EDID header, score = %d\n", score);
>> + DRM_DEBUG_DRIVER("Invalid EDID checksum %d\n", csum);
> No one on this file uses DRM_DEBUG_DRIVER (you use 2 calls here and one below).
>
> Also, during "normal operation" we try to calculate the checksum based
> on the fixed EDID header, so if we also print these messages here
> we're always going to have a message complaining about invalid
> checksum: either this one or the other that's already there. My
> bikeshed would be to just remove the messages you added here and below
> to not confuse users. Let's assume that the bad header is due to some
> communication/corruption error, and the HW manufacturers did not
> program an EDID with a bad header and a correct checksum based on bad
> header :)
Works for me. Messages have been removed.
>
>> + if (header_corrupt)
>> + *header_corrupt = 1;
>> + }
>> DRM_DEBUG("Fixing EDID header, your hardware may be failing\n");
>> memcpy(raw_edid, edid_header, sizeof(edid_header));
>> } else {
>> + if (header_corrupt) {
>> + DRM_DEBUG_DRIVER("Invalid EDID header\n");
>> + *header_corrupt = 1;
>> + }
> We don't ever set header_corrupt back to false, so if we ever get a
> corrupt header once, the header_corrupt flag will stay there even if
> it gets fixed somehow (such as a DP compliance tester starting to
> submit the correct header).
This is fixed as well. The flag now is reset to 0 at the end of the test
handler.
>
>> goto bad;
>> }
>> }
>> @@ -1129,7 +1147,7 @@ bool drm_edid_is_valid(struct edid *edid)
>> return false;
>>
>> for (i = 0; i <= edid->extensions; i++)
>> - if (!drm_edid_block_valid(raw + i * EDID_LENGTH, i, true))
>> + if (!drm_edid_block_valid(raw + i * EDID_LENGTH, i, true, NULL))
>> return false;
>>
>> return true;
>> @@ -1232,7 +1250,8 @@ struct edid *drm_do_get_edid(struct drm_connector *connector,
>> for (i = 0; i < 4; i++) {
>> if (get_edid_block(data, block, 0, EDID_LENGTH))
>> goto out;
>> - if (drm_edid_block_valid(block, 0, print_bad_edid))
>> + if (drm_edid_block_valid(block, 0, print_bad_edid,
>> + &connector->edid_header_corrupt))
>> break;
>> if (i == 0 && drm_edid_is_zero(block, EDID_LENGTH)) {
>> connector->null_edid_counter++;
>> @@ -1257,7 +1276,9 @@ struct edid *drm_do_get_edid(struct drm_connector *connector,
>> block + (valid_extensions + 1) * EDID_LENGTH,
>> j, EDID_LENGTH))
>> goto out;
>> - if (drm_edid_block_valid(block + (valid_extensions + 1) * EDID_LENGTH, j, print_bad_edid)) {
>> + if (drm_edid_block_valid(block + (valid_extensions + 1) * EDID_LENGTH, j,
>> + print_bad_edid,
>> + &connector->edid_header_corrupt)) {
> You can use NULL here since we're not handling block 0 anymore.
Fixed.
>
>> valid_extensions++;
>> break;
>> }
>> diff --git a/drivers/gpu/drm/drm_edid_load.c b/drivers/gpu/drm/drm_edid_load.c
>> index 732cb6f..1505494 100644
>> --- a/drivers/gpu/drm/drm_edid_load.c
>> +++ b/drivers/gpu/drm/drm_edid_load.c
>> @@ -216,7 +216,8 @@ static void *edid_load(struct drm_connector *connector, const char *name,
>> goto out;
>> }
>>
>> - if (!drm_edid_block_valid(edid, 0, print_bad_edid)) {
>> + if (!drm_edid_block_valid(edid, 0, print_bad_edid,
>> + &connector->edid_header_corrupt)) {
>> connector->bad_edid_counter++;
>> DRM_ERROR("Base block of EDID firmware \"%s\" is invalid ",
>> name);
>> @@ -229,7 +230,9 @@ static void *edid_load(struct drm_connector *connector, const char *name,
>> if (i != valid_extensions + 1)
>> memcpy(edid + (valid_extensions + 1) * EDID_LENGTH,
>> edid + i * EDID_LENGTH, EDID_LENGTH);
>> - if (drm_edid_block_valid(edid + i * EDID_LENGTH, i, print_bad_edid))
>> + if (drm_edid_block_valid(edid + i * EDID_LENGTH, i,
>> + print_bad_edid,
>> + &connector->edid_header_corrupt))
> Same here: not iterating over block 0.
Fixed
> Btw, why can't we just use NULL on edid_load?
I think it's at too high level again and the fix up code will get in the
way.
>
>> valid_extensions++;
>> }
>>
>> diff --git a/drivers/gpu/drm/i2c/tda998x_drv.c b/drivers/gpu/drm/i2c/tda998x_drv.c
>> index a9041d1..9c3d6b3 100644
>> --- a/drivers/gpu/drm/i2c/tda998x_drv.c
>> +++ b/drivers/gpu/drm/i2c/tda998x_drv.c
>> @@ -1106,7 +1106,7 @@ static uint8_t *do_get_edid(struct tda998x_priv *priv)
>> if (read_edid_block(priv, block, 0))
>> goto fail;
>>
>> - if (!drm_edid_block_valid(block, 0, print_bad_edid))
>> + if (!drm_edid_block_valid(block, 0, print_bad_edid, NULL))
>> goto fail;
>>
>> /* if there's no extensions, we're done */
>> @@ -1123,7 +1123,7 @@ static uint8_t *do_get_edid(struct tda998x_priv *priv)
>> if (read_edid_block(priv, ext_block, j))
>> goto fail;
>>
>> - if (!drm_edid_block_valid(ext_block, j, print_bad_edid))
>> + if (!drm_edid_block_valid(ext_block, j, print_bad_edid, NULL))
>> goto fail;
>>
>> valid_extensions++;
>> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
>> index e1d6e79..77b6b15 100644
>> --- a/drivers/gpu/drm/i915/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/intel_dp.c
>> @@ -3922,7 +3922,7 @@ intel_dp_check_link_status(struct intel_dp *intel_dp)
>> * 4.2.2.1 - EDID read required for all HPD events
>> */
>> edid_read = drm_get_edid(connector, adapter);
>> - if (!edid_read) {
>> + if (!edid_read || connector->edid_header_corrupt == 1) {
>> DRM_DEBUG_DRIVER("Invalid EDID detected\n");
>> }
>>
>> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
>> index 0261417..e31a4b3 100644
>> --- a/include/drm/drm_crtc.h
>> +++ b/include/drm/drm_crtc.h
>> @@ -719,6 +719,11 @@ struct drm_connector {
>> int null_edid_counter; /* needed to workaround some HW bugs where we get all 0s */
>> unsigned bad_edid_counter;
>>
>> + /* Flag for raw EDID header corruption - used in Displayport compliance testing
>> + * Displayport Link CTS Core 1.2 rev1.1 4.2.2.6
>> + */
>> + bool edid_header_corrupt;
>> +
>> struct dentry *debugfs_entry;
>>
>> struct drm_connector_state *state;
>> @@ -1436,7 +1441,8 @@ extern void drm_set_preferred_mode(struct drm_connector *connector,
>> int hpref, int vpref);
>>
>> extern int drm_edid_header_is_valid(const u8 *raw_edid);
>> -extern bool drm_edid_block_valid(u8 *raw_edid, int block, bool print_bad_edid);
>> +extern bool drm_edid_block_valid(u8 *raw_edid, int block, bool print_bad_edid, bool *header_corrupt);
>> +
>> extern bool drm_edid_is_valid(struct edid *edid);
>>
>> extern struct drm_tile_group *drm_mode_create_tile_group(struct drm_device *dev,
>> --
>> 1.9.1
>>
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>> dri-devel at lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/dri-devel
>
>
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