Re: [igt-dev] [PATCH i-g-t 1/2] lib/igt_chamelium: Sleep when doing autodiscovery

[Imre Deak <imre.deak@intel.com>]

On Wed, May 06, 2020 at 06:58:02PM +0300, Arkadiusz Hiler wrote:
> Autodiscovery was wrongly assuming that whenever we do chamelium_plug()
> the connector state change is immediate.
> 
> It was working most of the time for native connectors, but may explain
> some of the flip-flopping skips.
> 
> The problem got only more serious with the advent of LSPcons as USB-C,
> where we have much things happening on the signal path, introducing
> delays.
> 
> So for the sake of reliability this change introduces sleep(10) between
> plug and reprobe. The number is about 2 * the_most_pathological_case_observed.
> 
> Also the discovery step is performed only if there is no static port
> mapping set up. After the discovery is done, IGT prints the mapping
> ready to be pasted into .igtrc.
> 
> Cc: Kunal Joshi <kunal1.joshi@intel.com>
> Cc: Imre Deak <imre.deak@intel.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Signed-off-by: Arkadiusz Hiler <arkadiusz.hiler@intel.com>

Reviewed-by: Imre Deak <imre.deak@intel.com>

> ---
>  lib/igt_chamelium.c | 28 ++++++++++++++++++++++++++--
>  1 file changed, 26 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/igt_chamelium.c b/lib/igt_chamelium.c
> index c704b84f..28be5248 100644
> --- a/lib/igt_chamelium.c
> +++ b/lib/igt_chamelium.c
> @@ -82,6 +82,14 @@
>   *
>   */
>  
> +/*
> + * We cannot expect chamelium_plug() to take effect imediately.
> + *
> + * Especially with modern, more complex hardware where we may have LSPcons and
> + * USB controllers in the way.
> + */
> +#define CHAMELIUM_HOTPLUG_DETECTION_DELAY 10
> +
>  struct chamelium_edid {
>  	struct chamelium *chamelium;
>  	struct edid *base;
> @@ -2231,6 +2239,10 @@ static bool chamelium_autodiscover(struct chamelium *chamelium, int drm_fd)
>  		chamelium_plug(chamelium, port);
>  	}
>  
> +	igt_info("Sleeping %d seconds for the hotplug to take effect.\n",
> +		 CHAMELIUM_HOTPLUG_DETECTION_DELAY);
> +	sleep(CHAMELIUM_HOTPLUG_DETECTION_DELAY);
> +
>  	/* Reprobe connectors and build the mapping */
>  	res = drmModeGetResources(drm_fd);
>  	if (!res)
> @@ -2448,8 +2460,20 @@ struct chamelium *chamelium_init(int drm_fd)
>  	if (!chamelium_read_port_mappings(chamelium, drm_fd))
>  		goto error;
>  
> -	if (!chamelium_autodiscover(chamelium, drm_fd))
> -		goto error;
> +	if (chamelium->port_count == 0) {
> +		igt_info("Chamelium configured without port mapping, "
> +			 "performing autodiscovery\n");
> +
> +		if (!chamelium_autodiscover(chamelium, drm_fd))
> +			goto error;
> +
> +		if (chamelium->port_count != 0)
> +			igt_info("\nConsider adding the following to your .igtrc:\n");
> +		for (int i = 0; i < chamelium->port_count; ++i) {
> +			igt_info("[Chamelium:%s]\n", chamelium->ports[i].name);
> +			igt_info("ChameliumPortID=%d\n\n", chamelium->ports[i].id);
> +		}
> +	}
>  
>  	cleanup_instance = chamelium;
>  	igt_install_exit_handler(chamelium_exit_handler);
> -- 
> 2.25.2
> 
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