linux-kernel - Re: [PATCH v2 8/8] drm: zynqmp_dp: Add debugfs interface for compliance testing

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Date: Thu, 21 Mar 2024 12:08:44 -0400
From: Sean Anderson <sean.anderson@...ux.dev>
To: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Cc: Michal Simek <michal.simek@....com>, David Airlie <airlied@...il.com>,
 linux-kernel@...r.kernel.org, Daniel Vetter <daniel@...ll.ch>,
 linux-arm-kernel@...ts.infradead.org,
 Laurent Pinchart <laurent.pinchart@...asonboard.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v2 8/8] drm: zynqmp_dp: Add debugfs interface for
 compliance testing

On 3/20/24 03:49, Tomi Valkeinen wrote:
> On 20/03/2024 00:51, Sean Anderson wrote:
> 
>> +/**
>> + * enum test_pattern - Test patterns for test testing
> 
> "for test testing"? =)
> 
>> @@ -1655,6 +2321,9 @@ static void zynqmp_dp_hpd_irq_work_func(struct work_struct *work)
>>       u8 status[DP_LINK_STATUS_SIZE + 2];
>>       int err;
>>   +    if (READ_ONCE(dp->ignore_hpd))
>> +        return;
>> +
>>       mutex_lock(&dp->lock);
>>       err = drm_dp_dpcd_read(&dp->aux, DP_SINK_COUNT, status,
>>                      DP_LINK_STATUS_SIZE + 2);
> 
> Why do you need READ/WRITE_ONCE() for ignore_hpd?

It's not protected by dp->lock so we don't have to take it for
zynqmp_dp_hpd_work_func. Although maybe we should make a version of
zynqmp_dp_bridge_detect which assumes we already hold the lock.

--Sean