[PATCH] drm/amd/display: fix read errors pertaining to dp_lttpr_status_show()

[Aurabindo Pillai]

On 2/3/23 10:43, Hamza Mahfooz wrote:
> Currently, it is likely that we will read the relevant LTTPR caps after
> link training has completed (which can cause garbage data to be read),
> however according to the DP 2.0 spec that should be done before link
> training has commenced. So, instead of reading the registers on demand,
> use the values provided to us by DC.
>
> Signed-off-by: Hamza Mahfooz<hamza.mahfooz at amd.com>
> ---
>   .../amd/display/amdgpu_dm/amdgpu_dm_debugfs.c | 72 ++++++-------------
>   1 file changed, 22 insertions(+), 50 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c
> index e783082a4eef..cbc241596c1f 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c
> @@ -36,6 +36,7 @@
>   #include "dsc.h"
>   #include "link_hwss.h"
>   #include "dc/dc_dmub_srv.h"
> +#include "link/protocols/link_dp_capability.h"
>   
>   #ifdef CONFIG_DRM_AMD_SECURE_DISPLAY
>   #include "amdgpu_dm_psr.h"
> @@ -418,67 +419,38 @@ static ssize_t dp_phy_settings_read(struct file *f, char __user *buf,
>   	return result;
>   }
>   
> -static int dp_lttpr_status_show(struct seq_file *m, void *d)
> +static int dp_lttpr_status_show(struct seq_file *m, void *unused)
>   {
> -	char *data;
> -	struct amdgpu_dm_connector *connector = file_inode(m->file)->i_private;
> -	struct dc_link *link = connector->dc_link;
> -	uint32_t read_size = 1;
> -	uint8_t repeater_count = 0;
> +	struct drm_connector *connector = m->private;
> +	struct amdgpu_dm_connector *aconnector =
> +		to_amdgpu_dm_connector(connector);
> +	struct dc_lttpr_caps caps = aconnector->dc_link->dpcd_caps.lttpr_caps;
>   
> -	data = kzalloc(read_size, GFP_KERNEL);
> -	if (!data)
> -		return 0;
> +	if (connector->status != connector_status_connected)
> +		return -ENODEV;
>   
> -	dm_helpers_dp_read_dpcd(link->ctx, link, 0xF0002, data, read_size);
> +	seq_printf(m, "phy repeater count: %u (raw: 0x%x)\n",
> +		   dp_parse_lttpr_repeater_count(caps.phy_repeater_cnt),
> +		   caps.phy_repeater_cnt);
>   
> -	switch ((uint8_t)*data) {
> -	case 0x80:
> -		repeater_count = 1;
> -		break;
> -	case 0x40:
> -		repeater_count = 2;
> -		break;
> -	case 0x20:
> -		repeater_count = 3;
> -		break;
> -	case 0x10:
> -		repeater_count = 4;
> -		break;
> -	case 0x8:
> -		repeater_count = 5;
> -		break;
> -	case 0x4:
> -		repeater_count = 6;
> -		break;
> -	case 0x2:
> -		repeater_count = 7;
> +	seq_puts(m, "phy repeater mode: ");
> +
> +	switch (caps.mode) {
> +	case DP_PHY_REPEATER_MODE_TRANSPARENT:
> +		seq_puts(m, "transparent");
>   		break;
> -	case 0x1:
> -		repeater_count = 8;
> +	case DP_PHY_REPEATER_MODE_NON_TRANSPARENT:
> +		seq_puts(m, "non-transparent");
>   		break;
> -	case 0x0:
> -		repeater_count = 0;
> +	case 0x00:
> +		seq_puts(m, "non lttpr");
>   		break;
>   	default:
> -		repeater_count = (uint8_t)*data;
> +		seq_printf(m, "read error (raw: 0x%x)", caps.mode);
>   		break;
>   	}
>   
> -	seq_printf(m, "phy repeater count: %d\n", repeater_count);
> -
> -	dm_helpers_dp_read_dpcd(link->ctx, link, 0xF0003, data, read_size);
> -
> -	if ((uint8_t)*data == 0x55)
> -		seq_printf(m, "phy repeater mode: transparent\n");
> -	else if ((uint8_t)*data == 0xAA)
> -		seq_printf(m, "phy repeater mode: non-transparent\n");
> -	else if ((uint8_t)*data == 0x00)
> -		seq_printf(m, "phy repeater mode: non lttpr\n");
> -	else
> -		seq_printf(m, "phy repeater mode: read error\n");
> -
> -	kfree(data);
> +	seq_puts(m, "\n");
>   	return 0;
>   }
>   


Reviewed-by: Aurabindo Pillai <aurabindo.pillai at amd.com>
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