dri-devel.lists.freedesktop.org archive mirror
 help / color / mirror / Atom feed
From: Hans de Goede <hdegoede@redhat.com>
To: Daniel Vetter <daniel.vetter@ffwll.ch>,
	DRI Development <dri-devel@lists.freedesktop.org>
Cc: Daniel Vetter <daniel.vetter@intel.com>,
	Intel Graphics Development <intel-gfx@lists.freedesktop.org>
Subject: Re: [PATCH 45/51] drm/gm12u320: Simplify upload work
Date: Sat, 22 Feb 2020 13:30:52 +0100	[thread overview]
Message-ID: <ffd15759-0b7b-fa3f-c670-e83ccdfe11fc@redhat.com> (raw)
In-Reply-To: <20200221210319.2245170-46-daniel.vetter@ffwll.ch>

Hi,

On 2/21/20 10:03 PM, Daniel Vetter wrote:
> Instead of having a work item that never stops (which really should be
> a kthread), with a dedicated workqueue to not upset anyone else, use a
> delayed work. A bunch of changes:
> 
> - We can throw out all the custom wakeup and requeue logic and state
>    tracking. If we schedule the work with a 0 delay it'll get
>    scheduled immediately.

I'm afraid that that is not true, from the kdoc of
queue_delayed_work_on()  (which the other functions are wrappers of) :

  * Return: %false if @work was already on a queue, %true otherwise.  If
  * @delay is zero and @dwork is idle, it will be scheduled for immediate
  * execution.

And since the work gets scheduled with IDLE_TIMEOUT at the end of
the (modified) gm12u320_fb_update_work, it will not be idle when
gm12u320_fb_mark_dirty() does the schedule with 0 timeout, so it
will stay scheduled at the old IDLE_TIMEOUT and we will get a
very low framerate.

Instead we could use mod_delayed_work_on in the case where we want
0 timeout, that will behave as queue_delayed_work_on() when the work
has not been scheduled yet and it will modify the timeout otherwise.

This will still allow us to get rid of the waitq.

###

More in general though I'm not sure if getting rid of having our own
workqueue is a good idea (getting rid of the waitq is still a nice
cleanup). These projectors can be connected over USB2, and we send 20
blocks for a frame update. For each block we send a command + data
+ readback status, the data part does not fit in a single USB 2 timeslice
so that takes 2 ms + 1 ms for the command + 1ms of the status, so this
takes aprox. 80 ms on an idle USB-2 bus, if the bus is in use things get
worse and this assumes instant turn around for all the commands from the
projector.

schedule_delayed_work() uses the system_wq and that is described in
the docs as:

  * system_wq is the one used by schedule[_delayed]_work[_on]().
  * Multi-CPU multi-threaded.  There are users which expect relatively
  * short queue flush time.  Don't queue works which can run for too
  * long.

Arguably 80 ms is way too long, which would bring us to:

  * system_long_wq is similar to system_wq but may host long running
  * works.  Queue flushing might take relatively long.

But when connected over USB-3 we can easily do 60 FPS and we really
don't want frame updates to be delayed by other long running works.

So neither of the standard available queues is really suitable
and thus we really should keep using our own queue for this IMHO.

Regards,

Hans







> 
> - Persistent state (frame & draw_status_timeout) need to be moved out
>    of the work.
> 
> - diff is bigger than the changes, biggest chunk is reindenting the
>    work fn because it lost its while loop.
> 
> Lots of code deleting as consequence all over. Specifically we can
> delete the drm_driver.release code now!
> 
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Hans de Goede <hdegoede@redhat.com>
> Cc: "Noralf Trønnes" <noralf@tronnes.org>
> ---
>   drivers/gpu/drm/tiny/gm12u320.c | 170 +++++++++++++-------------------
>   1 file changed, 67 insertions(+), 103 deletions(-)
> 
> diff --git a/drivers/gpu/drm/tiny/gm12u320.c b/drivers/gpu/drm/tiny/gm12u320.c
> index c22b2ee470eb..46f5cea335a7 100644
> --- a/drivers/gpu/drm/tiny/gm12u320.c
> +++ b/drivers/gpu/drm/tiny/gm12u320.c
> @@ -89,13 +89,12 @@ struct gm12u320_device {
>   	unsigned char                   *cmd_buf;
>   	unsigned char                   *data_buf[GM12U320_BLOCK_COUNT];
>   	struct {
> -		bool                     run;
> -		struct workqueue_struct *workq;
> -		struct work_struct       work;
> -		wait_queue_head_t        waitq;
> +		struct delayed_work       work;
>   		struct mutex             lock;
>   		struct drm_framebuffer  *fb;
>   		struct drm_rect          rect;
> +		int frame;
> +		int draw_status_timeout;
>   	} fb_update;
>   };
>   
> @@ -183,19 +182,9 @@ static int gm12u320_usb_alloc(struct gm12u320_device *gm12u320)
>   		       data_block_footer, DATA_BLOCK_FOOTER_SIZE);
>   	}
>   
> -	gm12u320->fb_update.workq = create_singlethread_workqueue(DRIVER_NAME);
> -	if (!gm12u320->fb_update.workq)
> -		return -ENOMEM;
> -
>   	return 0;
>   }
>   
> -static void gm12u320_usb_free(struct gm12u320_device *gm12u320)
> -{
> -	if (gm12u320->fb_update.workq)
> -		destroy_workqueue(gm12u320->fb_update.workq);
> -}
> -
>   static int gm12u320_misc_request(struct gm12u320_device *gm12u320,
>   				 u8 req_a, u8 req_b,
>   				 u8 arg_a, u8 arg_b, u8 arg_c, u8 arg_d)
> @@ -338,80 +327,76 @@ static void gm12u320_copy_fb_to_blocks(struct gm12u320_device *gm12u320)
>   static void gm12u320_fb_update_work(struct work_struct *work)
>   {
>   	struct gm12u320_device *gm12u320 =
> -		container_of(work, struct gm12u320_device, fb_update.work);
> -	int draw_status_timeout = FIRST_FRAME_TIMEOUT;
> +		container_of(to_delayed_work(work), struct gm12u320_device,
> +			     fb_update.work);
>   	int block, block_size, len;
> -	int frame = 0;
>   	int ret = 0;
>   
> -	while (gm12u320->fb_update.run) {
> -		gm12u320_copy_fb_to_blocks(gm12u320);
> -
> -		for (block = 0; block < GM12U320_BLOCK_COUNT; block++) {
> -			if (block == GM12U320_BLOCK_COUNT - 1)
> -				block_size = DATA_LAST_BLOCK_SIZE;
> -			else
> -				block_size = DATA_BLOCK_SIZE;
> -
> -			/* Send data command to device */
> -			memcpy(gm12u320->cmd_buf, cmd_data, CMD_SIZE);
> -			gm12u320->cmd_buf[8] = block_size & 0xff;
> -			gm12u320->cmd_buf[9] = block_size >> 8;
> -			gm12u320->cmd_buf[20] = 0xfc - block * 4;
> -			gm12u320->cmd_buf[21] = block | (frame << 7);
> -
> -			ret = usb_bulk_msg(gm12u320->udev,
> -				usb_sndbulkpipe(gm12u320->udev, DATA_SND_EPT),
> -				gm12u320->cmd_buf, CMD_SIZE, &len,
> -				CMD_TIMEOUT);
> -			if (ret || len != CMD_SIZE)
> -				goto err;
> -
> -			/* Send data block to device */
> -			ret = usb_bulk_msg(gm12u320->udev,
> -				usb_sndbulkpipe(gm12u320->udev, DATA_SND_EPT),
> -				gm12u320->data_buf[block], block_size,
> -				&len, DATA_TIMEOUT);
> -			if (ret || len != block_size)
> -				goto err;
> -
> -			/* Read status */
> -			ret = usb_bulk_msg(gm12u320->udev,
> -				usb_rcvbulkpipe(gm12u320->udev, DATA_RCV_EPT),
> -				gm12u320->cmd_buf, READ_STATUS_SIZE, &len,
> -				CMD_TIMEOUT);
> -			if (ret || len != READ_STATUS_SIZE)
> -				goto err;
> -		}
> +	gm12u320_copy_fb_to_blocks(gm12u320);
> +
> +	for (block = 0; block < GM12U320_BLOCK_COUNT; block++) {
> +		if (block == GM12U320_BLOCK_COUNT - 1)
> +			block_size = DATA_LAST_BLOCK_SIZE;
> +		else
> +			block_size = DATA_BLOCK_SIZE;
> +
> +		/* Send data command to device */
> +		memcpy(gm12u320->cmd_buf, cmd_data, CMD_SIZE);
> +		gm12u320->cmd_buf[8] = block_size & 0xff;
> +		gm12u320->cmd_buf[9] = block_size >> 8;
> +		gm12u320->cmd_buf[20] = 0xfc - block * 4;
> +		gm12u320->cmd_buf[21] =
> +			block | (gm12u320->fb_update.frame << 7);
>   
> -		/* Send draw command to device */
> -		memcpy(gm12u320->cmd_buf, cmd_draw, CMD_SIZE);
>   		ret = usb_bulk_msg(gm12u320->udev,
>   			usb_sndbulkpipe(gm12u320->udev, DATA_SND_EPT),
> -			gm12u320->cmd_buf, CMD_SIZE, &len, CMD_TIMEOUT);
> +			gm12u320->cmd_buf, CMD_SIZE, &len,
> +			CMD_TIMEOUT);
>   		if (ret || len != CMD_SIZE)
>   			goto err;
>   
> +		/* Send data block to device */
> +		ret = usb_bulk_msg(gm12u320->udev,
> +			usb_sndbulkpipe(gm12u320->udev, DATA_SND_EPT),
> +			gm12u320->data_buf[block], block_size,
> +			&len, DATA_TIMEOUT);
> +		if (ret || len != block_size)
> +			goto err;
> +
>   		/* Read status */
>   		ret = usb_bulk_msg(gm12u320->udev,
>   			usb_rcvbulkpipe(gm12u320->udev, DATA_RCV_EPT),
>   			gm12u320->cmd_buf, READ_STATUS_SIZE, &len,
> -			draw_status_timeout);
> +			CMD_TIMEOUT);
>   		if (ret || len != READ_STATUS_SIZE)
>   			goto err;
> -
> -		draw_status_timeout = CMD_TIMEOUT;
> -		frame = !frame;
> -
> -		/*
> -		 * We must draw a frame every 2s otherwise the projector
> -		 * switches back to showing its logo.
> -		 */
> -		wait_event_timeout(gm12u320->fb_update.waitq,
> -				   !gm12u320->fb_update.run ||
> -					gm12u320->fb_update.fb != NULL,
> -				   IDLE_TIMEOUT);
>   	}
> +
> +	/* Send draw command to device */
> +	memcpy(gm12u320->cmd_buf, cmd_draw, CMD_SIZE);
> +	ret = usb_bulk_msg(gm12u320->udev,
> +		usb_sndbulkpipe(gm12u320->udev, DATA_SND_EPT),
> +		gm12u320->cmd_buf, CMD_SIZE, &len, CMD_TIMEOUT);
> +	if (ret || len != CMD_SIZE)
> +		goto err;
> +
> +	/* Read status */
> +	ret = usb_bulk_msg(gm12u320->udev,
> +		usb_rcvbulkpipe(gm12u320->udev, DATA_RCV_EPT),
> +		gm12u320->cmd_buf, READ_STATUS_SIZE, &len,
> +		gm12u320->fb_update.draw_status_timeout);
> +	if (ret || len != READ_STATUS_SIZE)
> +		goto err;
> +
> +	gm12u320->fb_update.draw_status_timeout = CMD_TIMEOUT;
> +	gm12u320->fb_update.frame = !gm12u320->fb_update.frame;
> +
> +	/*
> +	 * We must draw a frame every 2s otherwise the projector
> +	 * switches back to showing its logo.
> +	 */
> +	schedule_delayed_work(&gm12u320->fb_update.work, IDLE_TIMEOUT);
> +
>   	return;
>   err:
>   	/* Do not log errors caused by module unload or device unplug */
> @@ -446,36 +431,24 @@ static void gm12u320_fb_mark_dirty(struct drm_framebuffer *fb,
>   	mutex_unlock(&gm12u320->fb_update.lock);
>   
>   	if (wakeup)
> -		wake_up(&gm12u320->fb_update.waitq);
> +		schedule_delayed_work(&gm12u320->fb_update.work, 0);
>   
>   	if (old_fb)
>   		drm_framebuffer_put(old_fb);
>   }
>   
> -static void gm12u320_start_fb_update(struct gm12u320_device *gm12u320)
> -{
> -	mutex_lock(&gm12u320->fb_update.lock);
> -	gm12u320->fb_update.run = true;
> -	mutex_unlock(&gm12u320->fb_update.lock);
> -
> -	queue_work(gm12u320->fb_update.workq, &gm12u320->fb_update.work);
> -}
> -
>   static void gm12u320_stop_fb_update(struct gm12u320_device *gm12u320)
>   {
> -	mutex_lock(&gm12u320->fb_update.lock);
> -	gm12u320->fb_update.run = false;
> -	mutex_unlock(&gm12u320->fb_update.lock);
> +	struct drm_framebuffer *old_fb;
>   
> -	wake_up(&gm12u320->fb_update.waitq);
> -	cancel_work_sync(&gm12u320->fb_update.work);
> +	cancel_delayed_work_sync(&gm12u320->fb_update.work);
>   
>   	mutex_lock(&gm12u320->fb_update.lock);
> -	if (gm12u320->fb_update.fb) {
> -		drm_framebuffer_put(gm12u320->fb_update.fb);
> -		gm12u320->fb_update.fb = NULL;
> -	}
> +	old_fb = gm12u320->fb_update.fb;
> +	gm12u320->fb_update.fb = NULL;
>   	mutex_unlock(&gm12u320->fb_update.lock);
> +
> +	drm_framebuffer_put(old_fb);
>   }
>   
>   static int gm12u320_set_ecomode(struct gm12u320_device *gm12u320)
> @@ -583,11 +556,11 @@ static void gm12u320_pipe_enable(struct drm_simple_display_pipe *pipe,
>   				 struct drm_crtc_state *crtc_state,
>   				 struct drm_plane_state *plane_state)
>   {
> -	struct gm12u320_device *gm12u320 = pipe->crtc.dev->dev_private;
>   	struct drm_rect rect = { 0, 0, GM12U320_USER_WIDTH, GM12U320_HEIGHT };
> +	struct gm12u320_device *gm12u320 = pipe->crtc.dev->dev_private;
>   
> +	gm12u320->fb_update.draw_status_timeout = FIRST_FRAME_TIMEOUT;
>   	gm12u320_fb_mark_dirty(plane_state->fb, &rect);
> -	gm12u320_start_fb_update(gm12u320);
>   }
>   
>   static void gm12u320_pipe_disable(struct drm_simple_display_pipe *pipe)
> @@ -622,13 +595,6 @@ static const uint64_t gm12u320_pipe_modifiers[] = {
>   	DRM_FORMAT_MOD_INVALID
>   };
>   
> -static void gm12u320_driver_release(struct drm_device *dev)
> -{
> -	struct gm12u320_device *gm12u320 = dev->dev_private;
> -
> -	gm12u320_usb_free(gm12u320);
> -}
> -
>   DEFINE_DRM_GEM_FOPS(gm12u320_fops);
>   
>   static struct drm_driver gm12u320_drm_driver = {
> @@ -640,7 +606,6 @@ static struct drm_driver gm12u320_drm_driver = {
>   	.major		 = DRIVER_MAJOR,
>   	.minor		 = DRIVER_MINOR,
>   
> -	.release	 = gm12u320_driver_release,
>   	.fops		 = &gm12u320_fops,
>   	DRM_GEM_SHMEM_DRIVER_OPS,
>   };
> @@ -670,9 +635,8 @@ static int gm12u320_usb_probe(struct usb_interface *interface,
>   		return -ENOMEM;
>   
>   	gm12u320->udev = interface_to_usbdev(interface);
> -	INIT_WORK(&gm12u320->fb_update.work, gm12u320_fb_update_work);
> +	INIT_DELAYED_WORK(&gm12u320->fb_update.work, gm12u320_fb_update_work);
>   	mutex_init(&gm12u320->fb_update.lock);
> -	init_waitqueue_head(&gm12u320->fb_update.waitq);
>   
>   	dev = &gm12u320->dev;
>   	ret = devm_drm_dev_init(&interface->dev, dev, &gm12u320_drm_driver);
> 

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

  reply	other threads:[~2020-02-22 12:31 UTC|newest]

Thread overview: 77+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-21 21:02 [PATCH 00/51] drm managed resources, v2 Daniel Vetter
2020-02-21 21:02 ` [PATCH 01/51] mm/sl[uo]b: export __kmalloc_track(_node)_caller Daniel Vetter
2020-02-21 21:02 ` [PATCH 02/51] drm/i915: Don't clear drvdata in ->release Daniel Vetter
2020-02-21 21:36   ` Chris Wilson
2020-02-22  9:48     ` Daniel Vetter
2020-02-22  9:50       ` Daniel Vetter
2020-02-21 21:02 ` [PATCH 03/51] drm: add managed resources tied to drm_device Daniel Vetter
2020-02-25 10:27   ` Andrzej Hajda
2020-02-25 15:03     ` Daniel Vetter
2020-02-26  9:21       ` Andrzej Hajda
2020-02-26 10:21         ` Daniel Vetter
2020-02-26 14:38           ` Andrzej Hajda
2020-02-21 21:02 ` [PATCH 04/51] drm: Set final_kfree in drm_dev_alloc Daniel Vetter
2020-02-21 21:02 ` [PATCH 05/51] drm/mipi_dbi: Use drmm_add_final_kfree in all drivers Daniel Vetter
2020-02-21 21:02 ` [PATCH 06/51] drm/udl: Use drmm_add_final_kfree Daniel Vetter
2020-02-21 21:02 ` [PATCH 07/51] drm/qxl: " Daniel Vetter
2020-02-21 21:02 ` [PATCH 08/51] drm/i915: " Daniel Vetter
2020-02-21 21:02 ` [PATCH 09/51] drm/cirrus: " Daniel Vetter
2020-02-21 21:02 ` [PATCH 10/51] drm/v3d: " Daniel Vetter
2020-02-21 21:02 ` [PATCH 11/51] drm/tidss: " Daniel Vetter
2020-02-23 18:50   ` Jyri Sarha
2020-02-21 21:02 ` [PATCH 12/51] drm/mcde: " Daniel Vetter
2020-02-21 21:02 ` [PATCH 13/51] drm/vgem: " Daniel Vetter
2020-02-21 21:02 ` [PATCH 14/51] drm/vkms: " Daniel Vetter
2020-02-21 21:02 ` [PATCH 15/51] drm/repaper: " Daniel Vetter
2020-02-21 21:02 ` [PATCH 16/51] drm/inigenic: " Daniel Vetter
2020-02-21 21:02 ` [PATCH 17/51] drm/gm12u320: " Daniel Vetter
2020-02-22 11:36   ` Hans de Goede
2020-02-21 21:02 ` [PATCH 18/51] drm/<drivers>: " Daniel Vetter
2020-02-22 15:16   ` Russell King - ARM Linux admin
2020-02-27 17:46     ` Daniel Vetter
2020-02-21 21:02 ` [PATCH 19/51] drm: Cleanups after drmm_add_final_kfree rollout Daniel Vetter
2020-02-21 21:02 ` [PATCH 20/51] drm: Handle dev->unique with drmm_ Daniel Vetter
2020-02-21 21:02 ` [PATCH 21/51] drm: Use drmm_ for drm_dev_init cleanup Daniel Vetter
2020-02-21 21:02 ` [PATCH 22/51] drm: manage drm_minor cleanup with drmm_ Daniel Vetter
2020-02-21 21:02 ` [PATCH 23/51] drm: Manage drm_gem_init " Daniel Vetter
2020-02-21 21:02 ` [PATCH 24/51] drm: Manage drm_vblank_cleanup " Daniel Vetter
2020-02-21 21:02 ` [PATCH 25/51] drm: Garbage collect drm_dev_fini Daniel Vetter
2020-02-21 21:02 ` [PATCH 26/51] drm: Manage drm_mode_config_init with drmm_ Daniel Vetter
2020-02-23 15:17   ` Noralf Trønnes
2020-02-21 21:02 ` [PATCH 27/51] drm/bochs: Remove leftover drm_atomic_helper_shutdown Daniel Vetter
2020-02-21 21:02 ` [PATCH 28/51] drm/bochs: Drop explicit drm_mode_config_cleanup Daniel Vetter
2020-02-21 21:02 ` [PATCH 29/51] drm/cirrus: Drop explicit drm_mode_config_cleanup call Daniel Vetter
2020-02-21 21:02 ` [PATCH 30/51] drm/cirrus: Fully embrace devm_ Daniel Vetter
2020-02-21 21:02 ` [PATCH 31/51] drm/ingenic: Drop explicit drm_mode_config_cleanup call Daniel Vetter
2020-02-21 21:03 ` [PATCH 32/51] drm/mcde: " Daniel Vetter
2020-02-21 21:03 ` [PATCH 33/51] drm/mcde: More devm_drm_dev_init Daniel Vetter
2020-02-21 21:03 ` [PATCH 34/51] drm/meson: Drop explicit drm_mode_config_cleanup call Daniel Vetter
2020-02-21 21:03 ` [PATCH 35/51] drm/pl111: " Daniel Vetter
2020-02-21 21:03 ` [PATCH 36/51] drm/rcar-du: " Daniel Vetter
2020-02-21 21:03 ` [PATCH 37/51] drm/rockchip: " Daniel Vetter
2020-02-24 19:13   ` Francesco Lavra
2020-02-24 20:37     ` Daniel Vetter
2020-02-21 21:03 ` [PATCH 38/51] drm/stm: " Daniel Vetter
2020-02-21 21:03 ` [PATCH 39/51] drm/shmob: " Daniel Vetter
2020-02-21 21:03 ` [PATCH 40/51] drm/mtk: " Daniel Vetter
2020-02-21 21:03 ` [PATCH 41/51] drm/tidss: " Daniel Vetter
2020-02-23 18:50   ` Jyri Sarha
2020-02-21 21:03 ` [PATCH 42/51] drm/gm12u320: More drmm_ Daniel Vetter
2020-02-22 12:10   ` Hans de Goede
2020-02-21 21:03 ` [PATCH 43/51] drm/gm12u320: Use devm_drm_dev_init Daniel Vetter
2020-02-22 12:10   ` Hans de Goede
2020-02-21 21:03 ` [PATCH 44/51] drm/gm12u320: Use helpers for shutdown/suspend/resume Daniel Vetter
2020-02-22 12:10   ` Hans de Goede
2020-02-21 21:03 ` [PATCH 45/51] drm/gm12u320: Simplify upload work Daniel Vetter
2020-02-22 12:30   ` Hans de Goede [this message]
2020-02-22 13:00     ` Daniel Vetter
2020-02-21 21:03 ` [PATCH 46/51] drm/repaper: Drop explicit drm_mode_config_cleanup call Daniel Vetter
2020-02-21 21:03 ` [PATCH 47/51] drm/mipi-dbi: Move drm_mode_config_init into mipi library Daniel Vetter
2020-02-21 21:03 ` [PATCH 48/51] drm/mipi-dbi: Drop explicit drm_mode_config_cleanup call Daniel Vetter
2020-02-21 21:03 ` [PATCH 49/51] drm/udl: " Daniel Vetter
2020-02-21 21:03 ` [PATCH 50/51] drm/udl: drop drm_driver.release hook Daniel Vetter
2020-02-21 21:03 ` [PATCH 51/51] drm: Add docs for managed resources Daniel Vetter
2020-02-27 18:14 [PATCH 00/51] drm managed resources, v3 Daniel Vetter
2020-02-27 18:15 ` [PATCH 45/51] drm/gm12u320: Simplify upload work Daniel Vetter
2020-02-27 19:04   ` Hans de Goede
2020-03-02 22:25 [PATCH 00/51] drm_device managed resources, v4 Daniel Vetter
2020-03-02 22:26 ` [PATCH 45/51] drm/gm12u320: Simplify upload work Daniel Vetter
2020-03-23 14:48 [PATCH 00/51] drm_device managed resources, v5 Daniel Vetter
2020-03-23 14:49 ` [PATCH 45/51] drm/gm12u320: Simplify upload work Daniel Vetter

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=ffd15759-0b7b-fa3f-c670-e83ccdfe11fc@redhat.com \
    --to=hdegoede@redhat.com \
    --cc=daniel.vetter@ffwll.ch \
    --cc=daniel.vetter@intel.com \
    --cc=dri-devel@lists.freedesktop.org \
    --cc=intel-gfx@lists.freedesktop.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).