linux-kernel - Re: [PATCH v4 RESEND 1/5] drm/dp_helper: Increase retry interval to 1000us

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Message-ID: <20160329082732.GL2510@phenom.ffwll.local>
Date:	Tue, 29 Mar 2016 10:27:33 +0200
From:	Daniel Vetter <daniel@...ll.ch>
To:	Lyude <cpaul@...hat.com>
Cc:	intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
	arthur.j.runyan@...el.com, open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 RESEND 1/5] drm/dp_helper: Increase retry interval to
 1000us

On Mon, Mar 28, 2016 at 10:33:22AM -0400, Lyude wrote:
> This is part of a patch series to migrate all of the workarounds for
> commonly seen behavior from bad sinks in intel_dp_dpcd_read_wake() to
> drm's DP helper.
> 
> Signed-off-by: Lyude <cpaul@...hat.com>
> ---
>  drivers/gpu/drm/drm_dp_helper.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index 7d58f59..d1128fb 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -160,7 +160,7 @@ int drm_dp_bw_code_to_link_rate(u8 link_bw)
>  }
>  EXPORT_SYMBOL(drm_dp_bw_code_to_link_rate);
>  
> -#define AUX_RETRY_INTERVAL 500 /* us */
> +#define AUX_RETRY_INTERVAL 1000 /* us */

Was this to adapt to the msleep(1) in the i915 function? If so it's kinda
wrong anyway, since an msleep(1) actually sleeps 1 jiffy, and on most
systems that's a lot more than 1 ms. If it all still works, I'd just drop
this patch here. I suspect that the magic is all in the more aggressive
retrying and the throwaway read, not in how long we actually wait.

On patches 2-5: Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>

>  
>  /**
>   * DOC: dp helpers
> -- 
> 2.5.5
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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