From: Daniel Vetter <daniel@ffwll.ch>
To: Robert Beckett <bob.beckett@collabora.com>
Cc: dri-devel@lists.freedesktop.org,
Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Maxime Ripard <maxime.ripard@bootlin.com>,
Sean Paul <sean@poorly.run>, David Airlie <airlied@linux.ie>,
Daniel Vetter <daniel@ffwll.ch>,
Philipp Zabel <p.zabel@pengutronix.de>,
Shawn Guo <shawnguo@kernel.org>,
Sascha Hauer <s.hauer@pengutronix.de>,
Pengutronix Kernel Team <kernel@pengutronix.de>,
Fabio Estevam <festevam@gmail.com>,
NXP Linux Team <linux-imx@nxp.com>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 3/4] drm/vblank: estimate vblank while disabling vblank if interrupt disabled
Date: Tue, 25 Jun 2019 22:11:34 +0200 [thread overview]
Message-ID: <20190625201134.GF12905@phenom.ffwll.local> (raw)
In-Reply-To: <b96132cef4b63118df1026a99b3c345692e3de26.1561483965.git.bob.beckett@collabora.com>
On Tue, Jun 25, 2019 at 06:59:14PM +0100, Robert Beckett wrote:
> If interrupts are disabled (e.g. via vblank_disable_fn) and we come to
> disable vblank, update the vblank count to best guess as to what it
> would be had the interrupts remained enabled, and update the timesamp to
> now.
>
> This avoids a stale vblank event being sent while disabling crtcs during
> atomic modeset.
>
> Fixes: 68036b08b91bc ("drm/vblank: Do not update vblank count if interrupts
> are already disabled.")
>
> Signed-off-by: Robert Beckett <bob.beckett@collabora.com>
> ---
> drivers/gpu/drm/drm_vblank.c | 16 +++++++++++++++-
> 1 file changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
> index 7dabb2bdb733..db68b8cbf797 100644
> --- a/drivers/gpu/drm/drm_vblank.c
> +++ b/drivers/gpu/drm/drm_vblank.c
> @@ -375,9 +375,23 @@ void drm_vblank_disable_and_save(struct drm_device *dev, unsigned int pipe)
> * interrupts were enabled. This avoids calling the ->disable_vblank()
> * operation in atomic context with the hardware potentially runtime
> * suspended.
> + * If interrupts are disabled (e.g. via blank_disable_fn) then make
> + * best guess as to what it would be now and make sure we have an up
> + * to date timestamp.
> */
> - if (!vblank->enabled)
> + if (!vblank->enabled) {
> + ktime_t now = ktime_get();
Would be nice to fake this a bit more accurately and round the timestamp
here to a multiple of the frame duration, i.e. ...
> + u32 diff = 0;
> + if (vblank->framedur_ns) {
> + u64 diff_ns = ktime_to_ns(ktime_sub(now, vblank->time));
> + diff = DIV_ROUND_CLOSEST_ULL(diff_ns,
> + vblank->framedur_ns);
> + }
now = vblank->time + diff * vblank_framedur_ns;
Picking the right macro for doing 64bit multiplies left to you :-)
> +
> + store_vblank(dev, pipe, diff, now, vblank->count);
> +
> goto out;
> + }
>
> /*
> * Update the count and timestamp to maintain the
Somewhat unhappy that we're duplicating this logic with
drm_update_vblank_count, but it's just 2 lines of math.
-Daniel
> --
> 2.18.0
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
next prev parent reply other threads:[~2019-06-25 20:11 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-25 17:59 [PATCH v3 0/4] handle vblank when disabling ctc with interrupt disabled (was [PATCH v2] drm/imx: correct order of crtc disable) Robert Beckett
2019-06-25 17:59 ` [PATCH v3 1/4] drm/vblank: warn on sending stale event Robert Beckett
2019-06-25 20:00 ` Daniel Vetter
2019-06-25 20:02 ` Daniel Vetter
2019-06-25 17:59 ` [PATCH v3 2/4] drm/imx: notify drm core before sending event during crtc disable Robert Beckett
2019-06-25 20:03 ` Daniel Vetter
2019-06-25 17:59 ` [PATCH v3 3/4] drm/vblank: estimate vblank while disabling vblank if interrupt disabled Robert Beckett
2019-06-25 20:11 ` Daniel Vetter [this message]
2019-06-26 13:27 ` Ville Syrjälä
2019-06-26 14:30 ` Daniel Vetter
2019-06-25 17:59 ` [PATCH v3 4/4] drm/imx: only send event on crtc disable if kept disabled Robert Beckett
2019-06-25 20:22 ` Daniel Vetter
2019-06-26 8:33 ` Philipp Zabel
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