V4L/DVB (12825): tm6000: I2C reading operations is not reliable on tm6000

tm6000 sometimes can't read from i2c, but this is currently required for
tuner-xc2028 to work.

This patch adds an option to tuner-xc2028 to not rely on i2c reading.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/common/tuners/tuner-xc2028.c

@@ -812,8 +812,14 @@ check_device:
 
 	/* Check firmware version against what we downloaded. */
 	if (priv->firm_version != ((version & 0xf0) << 4 | (version & 0x0f))) {
+		if (!priv->ctrl.read_not_reliable) {
 			tuner_err("Incorrect readback of firmware version.\n");
 			goto fail;
+		} else {
+			tuner_err("Returned an incorrect version. However, "
+				  "read is not reliable enough. Ignoring it.\n");
+			hwmodel = 3028;
+		}
 	}
 
 	/* Check that the tuner hardware model remains consistent over time. */

drivers/media/common/tuners/tuner-xc2028.h

@@ -40,6 +40,7 @@ struct xc2028_ctrl {
 	unsigned int		vhfbw7:1;
 	unsigned int		uhfbw8:1;
 	unsigned int		disable_power_mgmt:1;
+	unsigned int            read_not_reliable:1;
 	unsigned int		demod;
 	enum firmware_type	type:2;
 };

drivers/staging/tm6000/tm6000-cards.c

@@ -189,6 +189,7 @@ static void tm6000_config_tuner (struct tm6000_core *dev)
 			ctl.fname = "tm6000-xc3028.fw";
 
 		ctl.mts   = 1;
+		ctl.read_not_reliable = 1;
 
 		xc2028_cfg.tuner = TUNER_XC2028;
 		xc2028_cfg.priv  = &ctl;