diff options
| -rw-r--r-- | drivers/gpu/drm/display/drm_dp_dual_mode_helper.c | 51 |
1 files changed, 29 insertions, 22 deletions
diff --git a/drivers/gpu/drm/display/drm_dp_dual_mode_helper.c b/drivers/gpu/drm/display/drm_dp_dual_mode_helper.c index 3ea53bb67d3b..bd61e20770a5 100644 --- a/drivers/gpu/drm/display/drm_dp_dual_mode_helper.c +++ b/drivers/gpu/drm/display/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 |