Hey Tommaso,
On Wed, Jun 07, 2023 at 03:19:24PM +0200, Tommaso Merciai wrote:
> + alliedvision,lp2hs-delay-us:
> + maximum: 150000
> + description: |
> + Low power to high speed delay time.
> +
> + If the value is larger than 0, the camera forces a reset of all
> + D-PHY lanes for the duration specified by this property. All lanes
> + will transition to the low-power state and back to the high-speed
> + state after the delay. Otherwise the lanes will transition to and
> + remain in the high-speed state immediately after power on.
> +
> + This is meant to help CSI-2 receivers synchronizing their D-PHY
> + RX.
Since this new version was posted before I got a chance to reply, I
still don't think it makes sense to allow 0 & then special case it,
when testing for the presence of a property is trivial.
The property should describe some behaviour/property of the hardware,
not be a mechanism to convey what you want to write into registers.
I don't really get why you'd not do:
If present, the camera forces a reset of all D-PHY lanes, for the
duration specified by this property. All lanes will transition to
the low-power state and back to the high-speed state after the
delay.
Otherwise the lanes will transition to and remain in the high-speed
state immediately after power on.
> +static int alvium_get_dt_data(struct alvium_dev *alvium)
> +{
> + struct device *dev = &alvium->i2c_client->dev;
> + struct device_node *node = dev->of_node;
> + struct fwnode_handle *endpoint;
> + int ret = 0;
> +
> + if (!node)
> + return -EINVAL;
> +
> + ret = fwnode_property_read_u32(dev_fwnode(dev),
> + "alliedvision,lp2hs-delay-us",
> + &alvium->lp2hs_delay);
> + if (ret)
> + dev_info(dev, "lp2hs-delay-us not found\n");
And this print, which I also don't understand the presence of as
well behaving driver should be quiet, goes away.
Cheers,
Conor.
> +
> + endpoint = fwnode_graph_get_next_endpoint(dev_fwnode(dev), NULL);
> + if (!endpoint) {
> + dev_err(dev, "endpoint node not found\n");
> + return -EINVAL;
> + }
> +
> + if (v4l2_fwnode_endpoint_alloc_parse(endpoint, &alvium->ep)) {
> + dev_err(dev, "could not parse endpoint\n");
> + return 0;
> + }
> +
> + if (alvium->ep.bus_type != V4L2_MBUS_CSI2_DPHY) {
> + dev_err(dev, "unsupported bus type\n");
> + return -EINVAL;
> + }
> +
> + if (!alvium->ep.nr_of_link_frequencies) {
> + dev_err(dev, "no link frequencies defined");
> + return -EINVAL;
> + }
> +
> + dev_info(dev, "freq: %llu\n",
> + alvium->ep.link_frequencies[0]);
> + dev_info(dev, "lanes: %d\n",
> + alvium->ep.bus.mipi_csi2.num_data_lanes);
> +
> + return 0;
> +}
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