[PATCH 1/1] UBUNTU: SAUCE: drm/i915: Disable writing of TMDS_OE on Lenovo ThinkPad X1 series

[Hui Wang]

On 2017年12月16日 17:00, Aaron Ma wrote:
> BugLink: https://bugs.launchpad.net/bugs/1738523
>
> There is a hw design on Lenovo ThinkPad X1 yoga/carbon:
> Intel GEN9 display -> AlpineRidge -> PS8407 -> HDMI output
>
> When switch mode on this HDMI output, it failed to writing on
> I2C device 0x40/0x50. Then sometimes the HDMI output is disabled.
>
>  From Parade's support, tmds_oe is enabled by default, and keep it
> enabled to fix this issue.

Is it possible that after upgrading the BIOS or VBIOS, tmds_oe becomes 
disabled by default, then your patch will keep the tmds_oe disabled 
forever on Lenovo X1?

If it is not, I think it is safe to apply this workaround, then give my 
ACK here.

Regards,
Hui.
>
> Add a workaround to bypass this TMDS_OE writing on identified
> laptop models.
>
> Signed-off-by: Aaron Ma <aaron.ma at canonical.com>
> ---
>   drivers/gpu/drm/i915/i915_drv.h   |  3 +++
>   drivers/gpu/drm/i915/intel_bios.c | 18 ++++++++++++++++++
>   drivers/gpu/drm/i915/intel_hdmi.c |  5 +++++
>   3 files changed, 26 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 0d3848b4f000..46bc91ad6719 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2576,6 +2576,9 @@ struct drm_i915_private {
>   
>   	bool ipc_enabled;
>   
> +	/* Hack to bypass TMDS_OE write on DP->HDMI dongle */
> +	bool bypass_tmds_oe;
> +
>   	/* Used to save the pipe-to-encoder mapping for audio */
>   	struct intel_encoder *av_enc_map[I915_MAX_PIPES];
>   
> diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
> index f814359c86c9..0be1d38feaec 100644
> --- a/drivers/gpu/drm/i915/intel_bios.c
> +++ b/drivers/gpu/drm/i915/intel_bios.c
> @@ -29,6 +29,7 @@
>   #include <drm/drmP.h>
>   #include <drm/i915_drm.h>
>   #include "i915_drv.h"
> +#include <linux/dmi.h>
>   
>   #define _INTEL_BIOS_PRIVATE
>   #include "intel_vbt_defs.h"
> @@ -1481,6 +1482,22 @@ static const struct vbt_header *find_vbt(void __iomem *bios, size_t size)
>   	return NULL;
>   }
>   
> +#define DRM_DMI_PRODUCT_VERSION 0x6
> +
> +static void parse_product_info(struct drm_i915_private *dev_priv)
> +{
> +	const char *product_ver = dmi_get_system_info(DRM_DMI_PRODUCT_VERSION);
> +	if (!product_ver)
> +		return;
> +
> +	if (!strncmp(product_ver, "ThinkPad X1", 11)) {
> +		DRM_DEBUG_KMS("dmi: %s, Bypassing TMDS_OE write\n", product_ver);
> +		dev_priv->bypass_tmds_oe = true;
> +	}
> +
> +	return;
> +}
> +
>   /**
>    * intel_bios_init - find VBT and initialize settings from the BIOS
>    * @dev_priv: i915 device instance
> @@ -1537,6 +1554,7 @@ void intel_bios_init(struct drm_i915_private *dev_priv)
>   	parse_mipi_config(dev_priv, bdb);
>   	parse_mipi_sequence(dev_priv, bdb);
>   	parse_ddi_ports(dev_priv, bdb);
> +	parse_product_info(dev_priv);
>   
>   out:
>   	if (!vbt) {
> diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
> index ec0779a52d53..01837b9f7d76 100644
> --- a/drivers/gpu/drm/i915/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/intel_hdmi.c
> @@ -851,6 +851,11 @@ void intel_dp_dual_mode_set_tmds_output(struct intel_hdmi *hdmi, bool enable)
>   	if (hdmi->dp_dual_mode.type < DRM_DP_DUAL_MODE_TYPE2_DVI)
>   		return;
>   
> +	if (dev_priv->bypass_tmds_oe) {
> +		DRM_DEBUG_KMS("Bypassing TMDS_OE setting\n");
> +		return;
> +	}
> +
>   	DRM_DEBUG_KMS("%s DP dual mode adaptor TMDS output\n",
>   		      enable ? "Enabling" : "Disabling");
>