On Thu, Aug 22, 2024 at 10:09 PM Andy Shevchenko
[off-list ref] wrote:

On Thu, Aug 22, 2024 at 05:20:00PM +0800, Chen-Yu Tsai wrote:

quoted

This adds regulator management to the I2C OF component prober.
Components that the prober intends to probe likely require their
regulator supplies be enabled, and GPIOs be toggled to enable them or
bring them out of reset before they will respond to probe attempts.
GPIOs will be handled in the next patch.

Without specific knowledge of each component's resource names or
power sequencing requirements, the prober can only enable the
regulator supplies all at once, and toggle the GPIOs all at once.
Luckily, reset pins tend to be active low, while enable pins tend to
be active high, so setting the raw status of all GPIO pins to high
should work. The wait time before and after resources are enabled
are collected from existing drivers and device trees.

The prober collects resources from all possible components and enables
them together, instead of enabling resources and probing each component
one by one. The latter approach does not provide any boot time benefits
over simply enabling each component and letting each driver probe
sequentially.

The prober will also deduplicate the resources, since on a component
swap out or co-layout design, the resources are always the same.
While duplicate regulator supplies won't cause much issue, shared
GPIOs don't work reliably, especially with other drivers. For the
same reason, the prober will release the GPIOs before the successfully
probed component is actually enabled.

...

quoted

 /*

quoted

  * address responds.
  *
  * TODO:
- * - Support handling common regulators and GPIOs.
+ * - Support handling common GPIOs.

You can split this to two lines in the first place and have less churn in this
patch and the other one.

Ack.

quoted

  * - Support I2C muxes
  */

..

quoted

+/* Returns number of regulator supplies found for node, or error. */
+static int i2c_of_probe_get_regulator(struct device *dev, struct device_node *node,
+                                   struct i2c_of_probe_data *data)
+{
+     struct regulator_bulk_data *tmp, *new_regulators;
+     int ret;
+
+     ret = of_regulator_bulk_get_all(dev, node, &tmp);
+     if (ret <= 0)
+             return ret;

I would split this and explain 0 case.

Ack.

quoted

+     if (!data->regulators) {
+             data->regulators = tmp;
+             data->regulators_num = ret;
+             return ret;
+     };
+
+     new_regulators = krealloc(data->regulators,
+                               sizeof(*tmp) * (data->regulators_num + ret),

krealloc_array()

Ack. Somehow I didn't find this function while I was rewriting the code.

quoted

+                               GFP_KERNEL);
+     if (!new_regulators) {
+             regulator_bulk_free(ret, tmp);
+             return -ENOMEM;
+     }
+
+     data->regulators = new_regulators;

quoted

+     for (unsigned int i = 0; i < ret; i++)
+             memcpy(&data->regulators[data->regulators_num++], &tmp[i], sizeof(*tmp));

Seems like copying array to array, no? If so, can't be done in a single memcpy() call?

Ack.

quoted

+     return ret;
+}

...

quoted

+static int i2c_of_probe_get_res(struct device *dev, struct device_node *node,
+                             struct i2c_of_probe_data *data)
+{
+     struct property *prop;
+     int ret;
+
+     ret = i2c_of_probe_get_regulator(dev, node, data);
+     if (ret < 0) {
+             dev_err_probe(dev, ret, "Failed to get regulator supplies from %pOF\n", node);
+             goto err_cleanup;
+     }
+
+     return 0;
+
+err_cleanup:
+     i2c_of_probe_free_res(data);
+     return ret;
+}

Hmm... why not

static int i2c_of_probe_get_res(struct device *dev, struct device_node *node,
                                struct i2c_of_probe_data *data)
{
        struct property *prop;
        int ret;

        ret = i2c_of_probe_get_regulator(dev, node, data);
        if (ret < 0) {
                i2c_of_probe_free_res(data);
                return dev_err_probe(dev, ret, "Failed to get regulator supplies from %pOF\n", node);
        }

        return 0;
}

...

That would be more churn in the next patch, which introduces another
error condition requiring the same cleanup.

quoted

+static int i2c_of_probe_enable_res(struct device *dev, struct i2c_of_probe_data *data)
+{
+     int ret = 0;

Redundant assignment.

Ack.

quoted

+     dev_dbg(dev, "Enabling regulator supplies\n");
+
+     ret = regulator_bulk_enable(data->regulators_num, data->regulators);
+     if (ret)
+             return ret;
+
+     /* largest post-power-on pre-reset-deassert delay seen among drivers */
+     msleep(500);

How would we monitor if any [new] driver wants to use bigger timeout?

The assumption is that the person doing the integration should test for
this. This prober doesn't get called everywhere. It needs a driver to
call it, and that driver is written by someone for some specific platform.
Maybe I should explicitly spell that out in the function description?
Or even make it a parameter?

Also, having an arbitrarily large number here doesn't help platforms that
want to minimize boot time. On that front I'm also thinking about whether
it is possible to do a handover to the actual driver so that the latter
doesn't have to go through the whole power sequence again.

quoted

+     return 0;
+}

...

quoted

      struct i2c_adapter *i2c;
+     struct i2c_of_probe_data probe_data = {0};

Reversed xmas tree order?

OK...

'0' is not needed.

Ack.

...

quoted

+     /* Grab resources */
+     for_each_child_of_node_scoped(i2c_node, node) {
+             u32 addr;
+
+             if (!of_node_name_prefix(node, type))
+                     continue;

Is it third or fourth copy of this code? At some point you probably want

#define for_each_child_of_node_with_prefix_scoped()
        for_each_if(...)

(or equivalent)

Ack.


Thank you for the review.

ChenYu

quoted

+             if (of_property_read_u32(node, "reg", &addr))
+                     continue;
+
+             dev_dbg(dev, "Requesting resources for %pOF\n", node);
+             ret = i2c_of_probe_get_res(dev, node, &probe_data);
+             if (ret)
+                     return ret;
+     }

--
With Best Regards,
Andy Shevchenko