1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
|
diff --git a/drivers/gpu/drm/drm_dp_dual_mode_helper.c b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
index 3ea53bb67d3b..bd61e20770a5 100644
--- a/drivers/gpu/drm/drm_dp_dual_mode_helper.c
+++ b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
@@ -63,23 +63,45 @@
ssize_t drm_dp_dual_mode_read(struct i2c_adapter *adapter,
u8 offset, void *buffer, size_t size)
{
+ u8 zero = 0;
+ char *tmpbuf = NULL;
+ /*
+ * As sub-addressing is not supported by all adaptors,
+ * always explicitly read from the start and discard
+ * any bytes that come before the requested offset.
+ * This way, no matter whether the adaptor supports it
+ * or not, we'll end up reading the proper data.
+ */
struct i2c_msg msgs[] = {
{
.addr = DP_DUAL_MODE_SLAVE_ADDRESS,
.flags = 0,
.len = 1,
- .buf = &offset,
+ .buf = &zero,
},
{
.addr = DP_DUAL_MODE_SLAVE_ADDRESS,
.flags = I2C_M_RD,
- .len = size,
+ .len = size + offset,
.buf = buffer,
},
};
int ret;
+ if (offset) {
+ tmpbuf = kmalloc(size + offset, GFP_KERNEL);
+ if (!tmpbuf)
+ return -ENOMEM;
+
+ msgs[1].buf = tmpbuf;
+ }
+
ret = i2c_transfer(adapter, msgs, ARRAY_SIZE(msgs));
+ if (tmpbuf)
+ memcpy(buffer, tmpbuf + offset, size);
+
+ kfree(tmpbuf);
+
if (ret < 0)
return ret;
if (ret != ARRAY_SIZE(msgs))
@@ -208,18 +230,6 @@ enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(const struct drm_device *dev,
if (ret)
return DRM_DP_DUAL_MODE_UNKNOWN;
- /*
- * Sigh. Some (maybe all?) type 1 adaptors are broken and ack
- * the offset but ignore it, and instead they just always return
- * data from the start of the HDMI ID buffer. So for a broken
- * type 1 HDMI adaptor a single byte read will always give us
- * 0x44, and for a type 1 DVI adaptor it should give 0x00
- * (assuming it implements any registers). Fortunately neither
- * of those values will match the type 2 signature of the
- * DP_DUAL_MODE_ADAPTOR_ID register so we can proceed with
- * the type 2 adaptor detection safely even in the presence
- * of broken type 1 adaptors.
- */
ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_ADAPTOR_ID,
&adaptor_id, sizeof(adaptor_id));
drm_dbg_kms(dev, "DP dual mode adaptor ID: %02x (err %zd)\n", adaptor_id, ret);
@@ -233,11 +243,10 @@ enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(const struct drm_device *dev,
return DRM_DP_DUAL_MODE_TYPE2_DVI;
}
/*
- * If neither a proper type 1 ID nor a broken type 1 adaptor
- * as described above, assume type 1, but let the user know
- * that we may have misdetected the type.
+ * If not a proper type 1 ID, still assume type 1, but let
+ * the user know that we may have misdetected the type.
*/
- if (!is_type1_adaptor(adaptor_id) && adaptor_id != hdmi_id[0])
+ if (!is_type1_adaptor(adaptor_id))
drm_err(dev, "Unexpected DP dual mode adaptor ID %02x\n", adaptor_id);
}
@@ -343,10 +352,8 @@ EXPORT_SYMBOL(drm_dp_dual_mode_get_tmds_output);
* @enable: enable (as opposed to disable) the TMDS output buffers
*
* Set the state of the TMDS output buffers in the adaptor. For
- * type2 this is set via the DP_DUAL_MODE_TMDS_OEN register. As
- * some type 1 adaptors have problems with registers (see comments
- * in drm_dp_dual_mode_detect()) we avoid touching the register,
- * making this function a no-op on type 1 adaptors.
+ * type2 this is set via the DP_DUAL_MODE_TMDS_OEN register.
+ * Type1 adaptors do not support any register writes.
*
* Returns:
* 0 on success, negative error code on failure
|
