Re: [RFC PATCH v4 4/4] ptp_ocp: implement DPLL ops

[Jiri Pirko <jiri@resnulli.us>]

Fri, Dec 02, 2022 at 12:27:32PM CET, arkadiusz.kubalewski@intel.com wrote:
>>From: Jiri Pirko <jiri@resnulli.us>
>>Sent: Wednesday, November 30, 2022 1:41 PM
>>
>>Tue, Nov 29, 2022 at 10:37:24PM CET, vfedorenko@novek.ru wrote:
>>>From: Vadim Fedorenko <vadfed@fb.com>

[...]


>>>+static int ptp_ocp_dpll_get_attr(struct dpll_device *dpll, struct
>>dpll_attr *attr)
>>>+{
>>>+	struct ptp_ocp *bp = (struct ptp_ocp *)dpll_priv(dpll);
>>>+	int sync;
>>>+
>>>+	sync = ioread32(&bp->reg->status) & OCP_STATUS_IN_SYNC;
>>>+	dpll_attr_lock_status_set(attr, sync ? DPLL_LOCK_STATUS_LOCKED :
>>DPLL_LOCK_STATUS_UNLOCKED);
>>
>>get,set,confuse. This attr thing sucks, sorry :/
>
>Once again, I feel obligated to add some explanations :)
>
>getter is ops called by dpll subsystem, it requires data, so here value shall
>be set for the caller, right?
>Also have explained the reason why this attr struct and functions are done this
>way in the response to cover letter concerns.

Okay, I will react there.


>
>>
>>
>>>+
>>>+	return 0;
>>>+}
>>>+
>>>+static int ptp_ocp_dpll_pin_get_attr(struct dpll_device *dpll, struct
>>dpll_pin *pin,
>>>+				     struct dpll_pin_attr *attr)
>>>+{
>>>+	dpll_pin_attr_type_set(attr, DPLL_PIN_TYPE_EXT);
>>
>>This is exactly what I was talking about in the cover letter. This is
>>const, should be put into static struct and passed to
>>dpll_device_alloc().
>
>Actually this type or some other parameters might change in the run-time,

No. This should not change.
If the pin is SyncE port, it's that for all lifetime of pin. It cannot
turn to be a EXT/SMA connector all of the sudden. This should be
definitelly fixed, it's a device topology.

Can you explain the exact scenario when the change of personality of pin
can happen? Perhaps I'm missing something.



>depends on the device, it is up to the driver how it will handle any getter,
>if driver knows it won't change it could also have some static member and copy
>the data with: dpll_pin_attr_copy(...);
>
>>
>>
>>>+	return 0;
>>>+}
>>>+
>>>+static struct dpll_device_ops dpll_ops = {
>>>+	.get	= ptp_ocp_dpll_get_attr,
>>>+};
>>>+
>>>+static struct dpll_pin_ops dpll_pin_ops = {
>>>+	.get	= ptp_ocp_dpll_pin_get_attr,
>>>+};
>>>+
>>> static int
>>> ptp_ocp_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>>> {
>>>+	const u8 dpll_cookie[DPLL_COOKIE_LEN] = { "OCP" };
>>>+	char pin_desc[PIN_DESC_LEN];
>>> 	struct devlink *devlink;
>>>+	struct dpll_pin *pin;
>>> 	struct ptp_ocp *bp;
>>>-	int err;
>>>+	int err, i;
>>>
>>> 	devlink = devlink_alloc(&ptp_ocp_devlink_ops, sizeof(*bp), &pdev-
>>>dev);
>>> 	if (!devlink) {
>>>@@ -4230,6 +4263,20 @@ ptp_ocp_probe(struct pci_dev *pdev, const struct
>>pci_device_id *id)
>>>
>>> 	ptp_ocp_info(bp);
>>> 	devlink_register(devlink);
>>>+
>>>+	bp->dpll = dpll_device_alloc(&dpll_ops, DPLL_TYPE_PPS, dpll_cookie,
>>pdev->bus->number, bp, &pdev->dev);
>>>+	if (!bp->dpll) {
>>>+		dev_err(&pdev->dev, "dpll_device_alloc failed\n");
>>>+		goto out;
>>>+	}
>>>+	dpll_device_register(bp->dpll);
>>
>>You still have the 2 step init process. I believe it would be better to
>>just have dpll_device_create/destroy() to do it in one shot.
>
>For me either is ok, but due to pins alloc/register as explained below I would
>leave it as it is.

Please don't, it has no value. Just adds unnecesary code. Have it nice
and simple.


>
>>
>>
>>>+
>>>+	for (i = 0; i < 4; i++) {
>>>+		snprintf(pin_desc, PIN_DESC_LEN, "sma%d", i + 1);
>>>+		pin = dpll_pin_alloc(pin_desc, PIN_DESC_LEN);
>>>+		dpll_pin_register(bp->dpll, pin, &dpll_pin_ops, bp);
>>
>>Same here, no point of having 2 step init.
>
>The alloc of a pin is not required if the pin already exist and would be just
>registered with another dpll.

Please don't. Have a pin created on a single DPLL. Why you make things
compitated here? I don't follow.


>Once we decide to entirely drop shared pins idea this could be probably done,
>although other kernel code usually use this twostep approach?

No, it does not. It's is used whatever fits on the individual usecase.


>
>>
>>
>>>+	}
>>>+
>>> 	return 0;
>>
>>
>>Btw, did you consider having dpll instance here as and auxdev? It would
>>be suitable I believe. It is quite simple to do it. See following patch
>>as an example:
>
>I haven't think about it, definetly gonna take a look to see if there any
>benefits in ice.

Please do. The proper separation and bus/device modelling is at least
one of the benefits. The other one is that all dpll drivers would
happily live in drivers/dpll/ side by side.



>
>Thanks,
>Arkadiusz
>
>>
>>commit bd02fd76d1909637c95e8ef13e7fd1e748af910d
>>Author: Jiri Pirko <jiri@nvidia.com>
>>Date:   Mon Jul 25 10:29:17 2022 +0200
>>
>>    mlxsw: core_linecards: Introduce per line card auxiliary device
>>
>>
>>
>>
>>>
>>> out:
>>>@@ -4247,6 +4294,8 @@ ptp_ocp_remove(struct pci_dev *pdev)
>>> 	struct ptp_ocp *bp = pci_get_drvdata(pdev);
>>> 	struct devlink *devlink = priv_to_devlink(bp);
>>>
>>>+	dpll_device_unregister(bp->dpll);
>>>+	dpll_device_free(bp->dpll);
>>> 	devlink_unregister(devlink);
>>> 	ptp_ocp_detach(bp);
>>> 	pci_disable_device(pdev);
>>>--
>>>2.27.0
>>>