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    Subject[PATCH 3.5 08/62] drm/i915/dp: add native aux defer retry limit
    Date
    3.5.7.32 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Jani Nikula <jani.nikula@intel.com>

    commit f51a44b9a6c4982cc25bfb3727de9bb893621ebc upstream.

    Retrying indefinitely places too much trust on the aux implementation of
    the sink devices.

    Reported-by: Daniel Martin <consume.noise@gmail.com>
    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=71267
    Signed-off-by: Jani Nikula <jani.nikula@intel.com>
    Tested-by: Theodore Ts'o <tytso@mit.edu>
    Tested-by: Sree Harsha Totakura <freedesktop@h.totakura.in>
    Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
    [ luis: backported to 3.5: adjusted context ]
    Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
    ---
    drivers/gpu/drm/i915/intel_dp.c | 15 +++++++++++----
    1 file changed, 11 insertions(+), 4 deletions(-)

    diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
    index fa14b42..7632aa0 100644
    --- a/drivers/gpu/drm/i915/intel_dp.c
    +++ b/drivers/gpu/drm/i915/intel_dp.c
    @@ -493,6 +493,7 @@ intel_dp_aux_native_write(struct intel_dp *intel_dp,
    uint8_t msg[20];
    int msg_bytes;
    uint8_t ack;
    + int retry;

    intel_dp_check_edp(intel_dp);
    if (send_bytes > 16)
    @@ -503,18 +504,20 @@ intel_dp_aux_native_write(struct intel_dp *intel_dp,
    msg[3] = send_bytes - 1;
    memcpy(&msg[4], send, send_bytes);
    msg_bytes = send_bytes + 4;
    - for (;;) {
    + for (retry = 0; retry < 7; retry++) {
    ret = intel_dp_aux_ch(intel_dp, msg, msg_bytes, &ack, 1);
    if (ret < 0)
    return ret;
    if ((ack & AUX_NATIVE_REPLY_MASK) == AUX_NATIVE_REPLY_ACK)
    - break;
    + return send_bytes;
    else if ((ack & AUX_NATIVE_REPLY_MASK) == AUX_NATIVE_REPLY_DEFER)
    usleep_range(400, 500);
    else
    return -EIO;
    }
    - return send_bytes;
    +
    + DRM_ERROR("too many retries, giving up\n");
    + return -EIO;
    }

    /* Write a single byte to the aux channel in native mode */
    @@ -536,6 +539,7 @@ intel_dp_aux_native_read(struct intel_dp *intel_dp,
    int reply_bytes;
    uint8_t ack;
    int ret;
    + int retry;

    intel_dp_check_edp(intel_dp);
    msg[0] = AUX_NATIVE_READ << 4;
    @@ -546,7 +550,7 @@ intel_dp_aux_native_read(struct intel_dp *intel_dp,
    msg_bytes = 4;
    reply_bytes = recv_bytes + 1;

    - for (;;) {
    + for (retry = 0; retry < 7; retry++) {
    ret = intel_dp_aux_ch(intel_dp, msg, msg_bytes,
    reply, reply_bytes);
    if (ret == 0)
    @@ -563,6 +567,9 @@ intel_dp_aux_native_read(struct intel_dp *intel_dp,
    else
    return -EIO;
    }
    +
    + DRM_ERROR("too many retries, giving up\n");
    + return -EIO;
    }

    static int
    --
    1.9.0


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