linux-kernel - Re: [PATCH 1/2] drm/atomic: Allow vblank-enabled + self-refresh "disable"

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Message-ID: <Y7fH88gNfja364JD@kroah.com>
Date:   Fri, 6 Jan 2023 08:04:19 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Brian Norris <briannorris@...omium.org>
Cc:     Heiko Stübner <heiko@...ech.de>,
        Sean Paul <seanpaul@...omium.org>,
        Sandy Huang <hjc@...k-chips.com>,
        Michel Dänzer <michel.daenzer@...lbox.org>,
        linux-kernel@...r.kernel.org, linux-rockchip@...ts.infradead.org,
        dri-devel@...ts.freedesktop.org, stable@...r.kernel.org
Subject: Re: [PATCH 1/2] drm/atomic: Allow vblank-enabled + self-refresh
 "disable"

On Thu, Jan 05, 2023 at 05:40:17PM -0800, Brian Norris wrote:
> The self-refresh helper framework overloads "disable" to sometimes mean
> "go into self-refresh mode," and this mode activates automatically
> (e.g., after some period of unchanging display output). In such cases,
> the display pipe is still considered "on", and user-space is not aware
> that we went into self-refresh mode. Thus, users may expect that
> vblank-related features (such as DRM_IOCTL_WAIT_VBLANK) still work
> properly.
> 
> However, we trigger the WARN_ONCE() here if a CRTC driver tries to leave
> vblank enabled here.
> 
> Add a new exception, such that we allow CRTCs to be "disabled" (with
> self-refresh active) with vblank interrupts still enabled.
> 
> Cc: <stable@...r.kernel.org> # dependency for subsequent patch

"subsequent" doesn't mean much when it is committed, give it a name
perhaps?

thanks,

greg k-h