[Intel-gfx] [PATCH 1/2] drm: add retries for lspcon status check

[Pandiyan, Dhinakaran]

On Fri, 2017-08-11 at 18:58 +0530, Shashank Sharma wrote:
> It's an observation during some CI tests that few LSPCON chips
> respond slow while system is under load, and need some delay

Thanks for the patch. Can you please explain what you mean by load here?
I can't follow why an external chip would respond slow if the system is
under load.

> while reading current mode status using i2c-over-aux channel.
> 

Is there a fdo bug where I can see more CI logs?

The only log I saw has this pattern around the time where this error
occurs. I am not sure how GPU hangs affect AUX transactions. But, I
think we should investigate/fix the underlying problem instead of adding
delays.


[   78.758510] i915 0000:00:02.0: Resetting vcs0 after gpu hang
[   78.758922] [drm:i915_gem_reset_engine [i915]] context
kms_busy[1372]/0 marked guilty (score 19) banned? no
[   78.758941] [drm:i915_gem_reset_engine [i915]] resetting vcs0 to
restart from tail of request 0x62
[   78.758990] [drm:gen8_init_common_ring [i915]] Execlists enabled for
vcs0
[   78.759014] [drm:gen8_init_common_ring [i915]] Restarting vcs0:0 from
0x62
[   78.759482] [drm:intel_power_well_enable [i915]] enabling always-on
[   78.759499] [drm:intel_power_well_enable [i915]] enabling DC off
[   78.759908] [drm:gen9_set_dc_state [i915]] Setting DC state from 02
to 00
[   78.759932] [drm:intel_power_well_enable [i915]] enabling power well
2
[   78.759993] [drm:intel_atomic_commit_tail [i915]] [ENCODER:57:DDI B]
[   78.760021] [drm:intel_atomic_commit_tail [i915]] [ENCODER:59:DP-MST
A]
[   78.760079] [drm:intel_atomic_commit_tail [i915]] [ENCODER:60:DP-MST
B]
[   78.760107] [drm:intel_atomic_commit_tail [i915]] [ENCODER:61:DP-MST
C]
[   78.760136] [drm:intel_atomic_commit_tail [i915]] [ENCODER:64:DDI C]
[   78.760163] [drm:intel_atomic_commit_tail [i915]] [ENCODER:66:DP-MST
A]
[   78.760191] [drm:intel_atomic_commit_tail [i915]] [ENCODER:67:DP-MST
B]
[   78.760218] [drm:intel_atomic_commit_tail [i915]] [ENCODER:68:DP-MST
C]
[   78.760246] [drm:verify_single_dpll_state.isra.70 [i915]] DPLL 0
[   78.760275] [drm:verify_single_dpll_state.isra.70 [i915]] DPLL 1
[   78.760304] [drm:verify_single_dpll_state.isra.70 [i915]] DPLL 2
[   78.760332] [drm:verify_single_dpll_state.isra.70 [i915]] DPLL 3
[   78.760362] [drm:intel_enable_shared_dpll [i915]] enable DPLL 1
(active 1, on? 0) for crtc 36
[   78.760390] [drm:intel_enable_shared_dpll [i915]] enabling DPLL 1
[   78.762529] [drm:intel_power_well_enable [i915]] enabling DDI B IO
power well
[   78.763146] [drm:drm_dp_i2c_do_msg] native defer
[   78.764268] [drm:drm_dp_i2c_do_msg] native defer
[   78.765735] [drm:drm_dp_i2c_do_msg] native defer
[   78.766794] [drm:drm_dp_i2c_do_msg] native defer
[   78.767853] [drm:drm_dp_i2c_do_msg] native defer
[   78.768982] [drm:drm_dp_i2c_do_msg] native defer
[   78.770112] [drm:drm_dp_i2c_do_msg] native defer
[   78.771240] [drm:drm_dp_i2c_do_msg] native defer
[   78.772371] [drm:drm_dp_i2c_do_msg] native defer
[   78.773068] [drm:drm_dp_i2c_do_msg] too many retries, giving up
[   78.773507] [drm:drm_dp_i2c_do_msg] native defer
[   78.774531] [drm:drm_dp_i2c_do_msg] native defer
[   78.775629] [drm:drm_dp_i2c_do_msg] native defer
[   78.776668] [drm:drm_dp_i2c_do_msg] native defer
[   78.777710] [drm:drm_dp_i2c_do_msg] native defer
[   78.778810] [drm:drm_dp_i2c_do_msg] native defer
[   78.779907] [drm:drm_dp_i2c_do_msg] native defer
[   78.780585] [drm:drm_dp_i2c_do_msg] too many retries, giving up
[   78.780589] [drm:drm_lspcon_get_mode] *ERROR* LSPCON read(0x80, 0x41)
failed
[   78.780621] [drm:lspcon_wait_mode [i915]] *ERROR* Error reading
LSPCON mode
[   78.780646] [drm:lspcon_wait_mode [i915]] Current LSPCON mode INVALID



> This patch:
> - Adds few retries and delays before declaring a read
>   failure from LSPCON hardware.
> - Changes the debug level of the print from ERROR->DEBUG
>   whereas another patch in I915 will add an ERROR message
>   from the caller when we have timed out all our limits.
> 
> Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
> Cc: Imre Deak <imre.deak at intel.com>
> Signed-off-by: Shashank Sharma <shashank.sharma at intel.com>
> Signed-off-by: Mahesh Kumar <mahesh1.kumar at intel.com>
> ---
>  drivers/gpu/drm/drm_dp_dual_mode_helper.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_dual_mode_helper.c b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
> index 80e62f6..c63eac8 100644
> --- a/drivers/gpu/drm/drm_dp_dual_mode_helper.c
> +++ b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
> @@ -409,6 +409,7 @@ int drm_lspcon_get_mode(struct i2c_adapter *adapter,
>  			enum drm_lspcon_mode *mode)
>  {
>  	u8 data;
> +	u8 retry = 5;
>  	int ret = 0;
>  
>  	if (!mode) {
> @@ -417,10 +418,17 @@ int drm_lspcon_get_mode(struct i2c_adapter *adapter,
>  	}
>  
>  	/* Read Status: i2c over aux */
> -	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_LSPCON_CURRENT_MODE,
> -				    &data, sizeof(data));
> +	do {
> +		ret = drm_dp_dual_mode_read(adapter,
> +					    DP_DUAL_MODE_LSPCON_CURRENT_MODE,
> +					    &data, sizeof(data));
> +		if (!ret || !retry--)
> +			break;
> +		usleep_range(500, 1000);

Are these numbers from a spec? I think it'd be pertinent to mention the
source.

> +	} while (1);
> +
>  	if (ret < 0) {
> -		DRM_ERROR("LSPCON read(0x80, 0x41) failed\n");
> +		DRM_DEBUG_KMS("LSPCON read(0x80, 0x41) failed\n");
>  		return -EFAULT;
>  	}
>