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Subject: Re: [PATCH v3 2/4] media: meson: Add M2M driver for the Amlogic GE2D
 Accelerator Unit
To:     Hans Verkuil <hverkuil@xs4all.nl>
Cc:     linux-media@vger.kernel.org, linux-amlogic@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
References: <20201117084440.578540-1-narmstrong@baylibre.com>
 <20201117084440.578540-3-narmstrong@baylibre.com>
 <3ce8d325-9d6d-9327-b019-65aad3fb1e64@xs4all.nl>
From:   Neil Armstrong <narmstrong@baylibre.com>
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Organization: Baylibre
Message-ID: <81cd2c1b-cfc9-0167-0e72-9f47b0887369@baylibre.com>
Date:   Wed, 2 Dec 2020 15:56:03 +0100
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In-Reply-To: <3ce8d325-9d6d-9327-b019-65aad3fb1e64@xs4all.nl>
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Hi Hans,

On 02/12/2020 13:40, Hans Verkuil wrote:
> On 17/11/2020 09:44, Neil Armstrong wrote:
>> The GE2D is a 2D accelerator with various features like configurable blitter
>> with alpha blending, frame rotation, scaling, format conversion and colorspace
>> conversion.
>>
>> The driver implements a Memory2Memory VB2 V4L2 streaming device permitting:
>> - 0, 90, 180, 270deg rotation
>> - horizontal/vertical flipping
>> - source cropping
>> - destination compositing
>> - 32bit/24bit/16bit format conversion
>>
>> This adds the support for the GE2D version found in the AXG SoCs Family.
>>
>> The missing features are:
>> - Source scaling
>> - Colorspace conversion
>> - Advanced alpha blending & blitting options
>>
>> Is passes v4l2-compliance SHA: ea16a7ef13a902793a5c2626b0cefc4d956147f3, 64 bits, 64-bit time_t
>>
>> Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
>> ---
>>  drivers/media/platform/Kconfig                |   13 +
>>  drivers/media/platform/Makefile               |    2 +
>>  drivers/media/platform/meson/ge2d/Makefile    |    3 +
>>  drivers/media/platform/meson/ge2d/ge2d-regs.h |  360 ++++++
>>  drivers/media/platform/meson/ge2d/ge2d.c      | 1091 +++++++++++++++++
>>  5 files changed, 1469 insertions(+)
>>  create mode 100644 drivers/media/platform/meson/ge2d/Makefile
>>  create mode 100644 drivers/media/platform/meson/ge2d/ge2d-regs.h
>>  create mode 100644 drivers/media/platform/meson/ge2d/ge2d.c
>>

[...]

>> +
>> +#define DEFAULT_WIDTH	100
>> +#define DEFAULT_HEIGHT	100
> 
> That's a weird default value. I would expect to see some multiple of 8 here.

Sure, whatever the HW is quite flexible, I took 100x100 from the other 2D accelerator drivers actually.

[...]

>> +
>> +static void ge2d_stop_streaming(struct vb2_queue *vq)
>> +{
>> +	struct ge2d_ctx *ctx = vb2_get_drv_priv(vq);
>> +	struct vb2_v4l2_buffer *vbuf;
>> +
>> +	if (V4L2_TYPE_IS_OUTPUT(vq->type))
>> +		ctx->streamon_out = false;
>> +	else
>> +		ctx->streamon_cap = false;
> 
> Do you need streamon_out/cap? Can't you use vb2_start_streaming_called() instead?

Indeed, I'll switch to vb2_start_streaming_called & co.

[...]

>> +
>> +static int vidioc_try_fmt_out(struct file *file, void *priv, struct v4l2_format *f)
>> +{
>> +	const struct ge2d_fmt *fmt = find_fmt(f);
>> +
>> +	f->fmt.pix.field = V4L2_FIELD_NONE;
>> +	f->fmt.pix.pixelformat = fmt->fourcc;
>> +
>> +	if (f->fmt.pix.width > MAX_WIDTH)
>> +		f->fmt.pix.width = MAX_WIDTH;
>> +	if (f->fmt.pix.height > MAX_HEIGHT)
>> +		f->fmt.pix.height = MAX_HEIGHT;
>> +
>> +	if (f->fmt.pix.width < 0)
>> +		f->fmt.pix.width = 0;
>> +	if (f->fmt.pix.height < 0)
>> +		f->fmt.pix.height = 0;
> 
> width and height are unsigned, so this check is not needed.

Ok

[...]

>> +
>> +static int ge2d_s_ctrl(struct v4l2_ctrl *ctrl)
>> +{
>> +	struct ge2d_ctx *ctx = container_of(ctrl->handler, struct ge2d_ctx,
>> +					   ctrl_handler);
>> +	struct v4l2_pix_format fmt;
>> +	struct vb2_queue *vq;
>> +	unsigned long flags;
>> +
>> +	spin_lock_irqsave(&ctx->ge2d->ctrl_lock, flags);
>> +	switch (ctrl->id) {
>> +	case V4L2_CID_HFLIP:
>> +		ctx->hflip = ctrl->val;
>> +		break;
>> +	case V4L2_CID_VFLIP:
>> +		ctx->vflip = ctrl->val;
>> +		break;
>> +	case V4L2_CID_ROTATE:
>> +		vq = v4l2_m2m_get_vq(ctx->fh.m2m_ctx, V4L2_BUF_TYPE_VIDEO_CAPTURE);
>> +		if (vb2_is_busy(vq))
>> +			return -EBUSY;
> 
> This doesn't call spin_unlock_irqrestore()!
> 
> Do you need the spinlock at all? This function is already called with a mutex
> for ctrl->handler held. It's unusual to see a spinlock here.

Is device_run also called with ctrl->handler held ?

The spinlock is used to protect against concurrent re-config & run.

[...]

>> +
>> +	platform_set_drvdata(pdev, ge2d);
>> +	ge2d->m2m_dev = v4l2_m2m_init(&ge2d_m2m_ops);
>> +	if (IS_ERR(ge2d->m2m_dev)) {
>> +		v4l2_err(&ge2d->v4l2_dev, "Failed to init mem2mem device\n");
>> +		ret = PTR_ERR(ge2d->m2m_dev);
>> +		goto unreg_video_dev;
> 
> This should be goto rel_vdev.
> 
>> +	}
>> +
>> +	ret = video_register_device(vfd, VFL_TYPE_VIDEO, -1);
>> +	if (ret) {
>> +		v4l2_err(&ge2d->v4l2_dev, "Failed to register video device\n");
>> +		goto rel_vdev;
>> +	}
>> +
>> +	v4l2_info(&ge2d->v4l2_dev, "Registered %s as /dev/%s\n",
>> +		  vfd->name, video_device_node_name(vfd));
>> +
>> +	return 0;
>> +
>> +rel_vdev:
>> +	video_device_release(vfd);
>> +unreg_video_dev:
>> +	video_unregister_device(ge2d->vfd);
> 
> This makes no sense. If video_register_device() fails, then you
> call video_device_release(vfd), not video_unregister_device().
> 
> Just drop these two lines.

ok

> 
>> +unreg_v4l2_dev:
>> +	v4l2_device_unregister(&ge2d->v4l2_dev);
>> +disable_clks:
>> +	clk_disable_unprepare(ge2d->clk);
>> +
>> +	return ret;
>> +}
>> +
>> +static int ge2d_remove(struct platform_device *pdev)
>> +{
>> +	struct meson_ge2d *ge2d = platform_get_drvdata(pdev);
>> +
>> +	v4l2_m2m_release(ge2d->m2m_dev);
>> +	video_unregister_device(ge2d->vfd);
>> +	v4l2_device_unregister(&ge2d->v4l2_dev);
>> +
>> +	clk_disable_unprepare(ge2d->clk);
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct of_device_id meson_ge2d_match[] = {
>> +	{
>> +		.compatible = "amlogic,axg-ge2d",
>> +	},
>> +	{},
>> +};
>> +
>> +MODULE_DEVICE_TABLE(of, meson_ge2d_match);
>> +
>> +static struct platform_driver ge2d_drv = {
>> +	.probe = ge2d_probe,
>> +	.remove = ge2d_remove,
>> +	.driver = {
>> +		.name = "meson-ge2d",
>> +		.of_match_table = meson_ge2d_match,
>> +	},
>> +};
>> +
>> +module_platform_driver(ge2d_drv);
>> +
>> +MODULE_AUTHOR("Neil Armstrong <narmstrong@baylibre.com>");
>> +MODULE_DESCRIPTION("Amlogic 2D Graphic Acceleration Unit");
>> +MODULE_LICENSE("GPL");
>>
> 
> Regards,
> 
> 	Hans
> 

Thanks,
Neil