1 files changed, 18 insertions, 3 deletions

diff --git a/drivers/media/video/cx25840/cx25840-core.c b/drivers/media/video/cx25840/cx25840-core.c
index 56ead3d37926..904e9a5a9065 100644
--- a/drivers/media/video/cx25840/cx25840-core.c
+++ b/drivers/media/video/cx25840/cx25840-core.c
@@ -1598,14 +1598,29 @@ static u32 get_cx2388x_ident(struct i2c_client *client)
         /* Come out of digital power down */
         cx25840_write(client, 0x000, 0);
 
+        /* Detecting whether the part is cx23885/7/8 is more
+         * difficult than it needs to be. No ID register. Instead we
+         * probe certain registers indicated in the datasheets to look
+         * for specific defaults that differ between the silicon designs. */
+
+        /* It's either 885/7 if the IR Tx Clk Divider register exists */
         if (cx25840_read4(client, 0x204) & 0xffff) {
-                /* IR Tx Clk Divider register exists; chip must be a CX23885 */
-                ret = V4L2_IDENT_CX23885_AV;
+                /* CX23885 returns bogus repetitive byte values for the DIF,
+                 * which doesn't exist for it. (Ex. 8a8a8a8a or 31313131) */
+                ret = cx25840_read4(client, 0x300);
+                if (((ret & 0xffff0000) >> 16) == (ret & 0xffff)) {
+                        /* No DIF */
+                        ret = V4L2_IDENT_CX23885_AV;
+                } else {
+                        /* CX23887 has a broken DIF, but the registers
+                         * appear valid (but unsed), good enough to detect. */
+                        ret = V4L2_IDENT_CX23887_AV;
+                }
         } else if (cx25840_read4(client, 0x300) & 0x0fffffff) {
                 /* DIF PLL Freq Word reg exists; chip must be a CX23888 */
                 ret = V4L2_IDENT_CX23888_AV;
         } else {
-                /* A CX23887 A/V core has neither IR nor DIF */
+                v4l_err(client, "Unable to detect h/w, assuming cx23887\n");
                 ret = V4L2_IDENT_CX23887_AV;
         }