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Subject[18/38] drm/radeon/kms: add retry limits for native DP aux defer
3.0-stable review patch.  If anyone has any objections, please let us know.

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

From: Alex Deucher <alexander.deucher@amd.com>

commit 6375bda073724ead7df08746866b724b1799a295 upstream.

The previous code could potentially loop forever. Limit
the number of DP aux defer retries to 4 for native aux
transactions, same as i2c over aux transactions.

Noticed by: Brad Campbell <lists2009@fnarfbargle.com>

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: Brad Campbell <lists2009@fnarfbargle.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/gpu/drm/radeon/atombios_dp.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)

--- a/drivers/gpu/drm/radeon/atombios_dp.c
+++ b/drivers/gpu/drm/radeon/atombios_dp.c
@@ -115,6 +115,7 @@ static int radeon_dp_aux_native_write(st
u8 msg[20];
int msg_bytes = send_bytes + 4;
u8 ack;
+ unsigned retry;

if (send_bytes > 16)
return -1;
@@ -125,20 +126,20 @@ static int radeon_dp_aux_native_write(st
msg[3] = (msg_bytes << 4) | (send_bytes - 1);
memcpy(&msg[4], send, send_bytes);

- while (1) {
+ for (retry = 0; retry < 4; retry++) {
ret = radeon_process_aux_ch(dig_connector->dp_i2c_bus,
msg, msg_bytes, NULL, 0, delay, &ack);
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)
udelay(400);
else
return -EIO;
}

- return send_bytes;
+ return -EIO;
}

static int radeon_dp_aux_native_read(struct radeon_connector *radeon_connector,
@@ -149,13 +150,14 @@ static int radeon_dp_aux_native_read(str
int msg_bytes = 4;
u8 ack;
int ret;
+ unsigned retry;

msg[0] = address;
msg[1] = address >> 8;
msg[2] = AUX_NATIVE_READ << 4;
msg[3] = (msg_bytes << 4) | (recv_bytes - 1);

- while (1) {
+ for (retry = 0; retry < 4; retry++) {
ret = radeon_process_aux_ch(dig_connector->dp_i2c_bus,
msg, msg_bytes, recv, recv_bytes, delay, &ack);
if (ret < 0)
@@ -169,6 +171,8 @@ static int radeon_dp_aux_native_read(str
else
return -EIO;
}
+
+ return -EIO;
}

static void radeon_write_dpcd_reg(struct radeon_connector *radeon_connector,



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