drm/bridge/sii8620: fix loops in EDID fetch logic

[ Upstream commit 8e627a1b1ce8feb3e1da4428b71b9b4905f04888 ]

Function should constantly check if cable is connected and finish
in finite time.

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Maciej Purski <m.purski@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180115173357.31067-4-a.hajda@samsung.com
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/bridge/sil-sii8620.c b/drivers/gpu/drm/bridge/sil-sii8620.c
index 5131bfb..8b17a80 100644 (file)
--- a/drivers/gpu/drm/bridge/sil-sii8620.c
+++ b/drivers/gpu/drm/bridge/sil-sii8620.c
@@ -788,6 +788,7 @@ static void sii8620_burst_rx_all(struct sii8620 *ctx)
 static void sii8620_fetch_edid(struct sii8620 *ctx)
 {
        u8 lm_ddc, ddc_cmd, int3, cbus;
+       unsigned long timeout;
        int fetched, i;
        int edid_len = EDID_LENGTH;
        u8 *edid;
@@ -837,23 +838,31 @@ static void sii8620_fetch_edid(struct sii8620 *ctx)
                        REG_DDC_CMD, ddc_cmd | VAL_DDC_CMD_ENH_DDC_READ_NO_ACK
                );
 
-               do {
-                       int3 = sii8620_readb(ctx, REG_INTR3);
+               int3 = 0;
+               timeout = jiffies + msecs_to_jiffies(200);
+               for (;;) {
                        cbus = sii8620_readb(ctx, REG_CBUS_STATUS);
-
-                       if (int3 & BIT_DDC_CMD_DONE)
-                               break;
-
-                       if (!(cbus & BIT_CBUS_STATUS_CBUS_CONNECTED)) {
+                       if (~cbus & BIT_CBUS_STATUS_CBUS_CONNECTED) {
+                               kfree(edid);
+                               edid = NULL;
+                               goto end;
+                       }
+                       if (int3 & BIT_DDC_CMD_DONE) {
+                               if (sii8620_readb(ctx, REG_DDC_DOUT_CNT)
+                                   >= FETCH_SIZE)
+                                       break;
+                       } else {
+                               int3 = sii8620_readb(ctx, REG_INTR3);
+                       }
+                       if (time_is_before_jiffies(timeout)) {
+                               ctx->error = -ETIMEDOUT;
+                               dev_err(ctx->dev, "timeout during EDID read\n");
                                kfree(edid);
                                edid = NULL;
                                goto end;
                        }
-               } while (1);
-
-               sii8620_readb(ctx, REG_DDC_STATUS);
-               while (sii8620_readb(ctx, REG_DDC_DOUT_CNT) < FETCH_SIZE)
                        usleep_range(10, 20);
+               }
 
                sii8620_read_buf(ctx, REG_DDC_DATA, edid + fetched, FETCH_SIZE);
                if (fetched + FETCH_SIZE == EDID_LENGTH) {