drm/nouveau: bail out of auxch transaction if we repeatedly recieve defers

There's one known case where we never stop recieving DEFER, and loop here
forever.  Lets not do that..

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

diff --git a/drivers/gpu/drm/nouveau/nouveau_dp.c b/drivers/gpu/drm/nouveau/nouveau_dp.c
index f954ad9..deeb21c 100644 (file)
--- a/drivers/gpu/drm/nouveau/nouveau_dp.c
+++ b/drivers/gpu/drm/nouveau/nouveau_dp.c
@@ -483,7 +483,7 @@ nouveau_dp_auxch(struct nouveau_i2c_chan *auxch, int cmd, int addr,
        ctrl |= (cmd << NV50_AUXCH_CTRL_CMD_SHIFT);
        ctrl |= ((data_nr - 1) << NV50_AUXCH_CTRL_LEN_SHIFT);
 
-       for (;;) {
+       for (i = 0; i < 16; i++) {
                nv_wr32(dev, NV50_AUXCH_CTRL(index), ctrl | 0x80000000);
                nv_wr32(dev, NV50_AUXCH_CTRL(index), ctrl);
                nv_wr32(dev, NV50_AUXCH_CTRL(index), ctrl | 0x00010000);
@@ -502,6 +502,12 @@ nouveau_dp_auxch(struct nouveau_i2c_chan *auxch, int cmd, int addr,
                        break;
        }
 
+       if (i == 16) {
+               NV_ERROR(dev, "auxch DEFER too many times, bailing\n");
+               ret = -EREMOTEIO;
+               goto out;
+       }
+
        if (cmd & 1) {
                if ((stat & NV50_AUXCH_STAT_COUNT) != data_nr) {
                        ret = -EREMOTEIO;