Re: [PATCH] drm/amd/display: Ignore First MST Sideband Message Return Error

["Limonciello, Mario" <mario.limonciello@amd.com>]

On 7/11/2022 16:52, Rodrigo Siqueira wrote:
> From: Fangzhi Zuo <Jerry.Zuo@amd.com>
> 
> [why]
> The first MST sideband message returns AUX_RET_ERROR_HPD_DISCON on
> a certain Intel platform. Aux transaction is considered a failure if HPD
> unexpectedly pulled low. The actual aux transaction success in such
> case, hence do not return an error. Several Dell Intel-based Precision
> systems had this issue, for example, Precision 3260 and 3460.
> 
> [how]
> Not returning error when AUX_RET_ERROR_HPD_DISCON detected
> on the first sideband message.
> 
> Cc: Harry Wentland <harry.wentland@amd.com>
> Cc: Mario Limonciello <mario.limonciello@amd.com>
> Cc: Qian Fu <Qian.Fu@dell.com>
> Cc: stable@vger.kernel.org
> Signed-off-by: Fangzhi Zuo <Jerry.Zuo@amd.com>
> ---
>   .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 27 +++++++++++++++++++
>   .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h |  8 ++++++
>   .../display/amdgpu_dm/amdgpu_dm_mst_types.c   | 17 ++++++++++++
>   3 files changed, 52 insertions(+)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index de1c139ae279..e0af3d003b5c 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -72,6 +72,7 @@
>   #include <linux/pci.h>
>   #include <linux/firmware.h>
>   #include <linux/component.h>
> +#include <linux/dmi.h>
>   
>   #include <drm/drm_atomic.h>
>   #include <drm/drm_atomic_uapi.h>
> @@ -1400,6 +1401,29 @@ static bool dm_should_disable_stutter(struct pci_dev *pdev)
>   	return false;
>   }
>   
> +static const struct dmi_system_id hpd_disconnect_quirk_table[] = {
> +	{
> +		.matches = {
> +			DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
> +			DMI_MATCH(DMI_PRODUCT_NAME, "Precision 3660"),
> +		},
> +	},

I think two more matches are needed here for the other two products that 
are affected by this.

> +	{}
> +};
> +
> +void retrieve_dmi_info(struct amdgpu_display_manager *dm)
> +{
> +	const struct dmi_system_id *dmi_id;
> +
> +	dm->aux_hpd_discon_quirk = false;
> +
> +	dmi_id = dmi_first_match(hpd_disconnect_quirk_table);
> +	if (dmi_id) {
> +		dm->aux_hpd_discon_quirk = true;
> +		DRM_INFO("aux_hpd_discon_quirk attached\n");
> +	}
> +}
> +
>   static int amdgpu_dm_init(struct amdgpu_device *adev)
>   {
>   	struct dc_init_data init_data;
> @@ -1528,6 +1552,9 @@ static int amdgpu_dm_init(struct amdgpu_device *adev)
>   	init_data.flags.enable_mipi_converter_optimization = true;
>   
>   	INIT_LIST_HEAD(&adev->dm.da_list);
> +
> +	retrieve_dmi_info(&adev->dm);
> +
>   	/* Display Core create. */
>   	adev->dm.dc = dc_create(&init_data);
>   
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
> index e04e6b3f609f..33d66d4897dc 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
> @@ -547,6 +547,14 @@ struct amdgpu_display_manager {
>   	 * last successfully applied backlight values.
>   	 */
>   	u32 actual_brightness[AMDGPU_DM_MAX_NUM_EDP];
> +
> +	/**
> +	 * @aux_hpd_discon_quirk:
> +	 *
> +	 * quirk for hpd discon while aux is on-going.
> +	 * occurred on certain intel platform
> +	 */
> +	bool aux_hpd_discon_quirk;
>   };
>   
>   enum dsc_clock_force_state {
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> index 8237029cedf5..168d5676b657 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> @@ -56,6 +56,8 @@ static ssize_t dm_dp_aux_transfer(struct drm_dp_aux *aux,
>   	ssize_t result = 0;
>   	struct aux_payload payload;
>   	enum aux_return_code_type operation_result;
> +	struct amdgpu_device *adev;
> +	struct ddc_service *ddc;
>   
>   	if (WARN_ON(msg->size > 16))
>   		return -E2BIG;
> @@ -74,6 +76,21 @@ static ssize_t dm_dp_aux_transfer(struct drm_dp_aux *aux,
>   	result = dc_link_aux_transfer_raw(TO_DM_AUX(aux)->ddc_service, &payload,
>   				      &operation_result);
>   
> +	/*
> +	 * w/a on certain intel platform where hpd is unexpected to pull low during
> +	 * 1st sideband message transaction by return AUX_RET_ERROR_HPD_DISCON
> +	 * aux transaction is succuess in such case, therefore bypass the error
> +	 */
> +	ddc = TO_DM_AUX(aux)->ddc_service;
> +	adev = ddc->ctx->driver_context;
> +	if (adev->dm.aux_hpd_discon_quirk) {
> +		if (msg->address == DP_SIDEBAND_MSG_DOWN_REQ_BASE &&
> +			operation_result == AUX_RET_ERROR_HPD_DISCON) {
> +			result = 0;
> +			operation_result = AUX_RET_SUCCESS;
> +		}
> +	}
> +
>   	if (payload.write && result >= 0)
>   		result = msg->size;
>