RE: [RFC PATCH v7 12/12] memory: RAS2: Add memory RAS2 driver

[Shiju Jose]

Hi Daniel,

>-----Original Message-----
>From: Daniel Ferguson <danielf@xxxxxxxxxxxxxxxxxxxxxx>
>Sent: 28 March 2024 23:42
>To: Shiju Jose <shiju.jose@xxxxxxxxxx>; linux-cxl@xxxxxxxxxxxxxxx; linux-
>acpi@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx; dan.j.williams@xxxxxxxxx;
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>Subject: Re: [RFC PATCH v7 12/12] memory: RAS2: Add memory RAS2 driver
>
>> +/*
...
>> +
>> +static int ras2_probe(struct platform_device *pdev) {
>> +	int ret, id;
>> +	struct mbox_client *cl;
>> +	struct device *hw_scrub_dev;
>> +	struct ras2_context *ras2_ctx;
>> +	char scrub_name[RAS2_MAX_NAME_LENGTH];
>> +
>> +	ras2_ctx = devm_kzalloc(&pdev->dev, sizeof(*ras2_ctx), GFP_KERNEL);
>> +	if (!ras2_ctx)
>> +		return -ENOMEM;
>> +
>> +	ras2_ctx->dev = &pdev->dev;
>> +	ras2_ctx->ops = &ras2_hw_ops;
>> +	spin_lock_init(&ras2_ctx->spinlock);
>> +	platform_set_drvdata(pdev, ras2_ctx);
>> +
>> +	cl = &ras2_ctx->mbox_client;
>> +	/* Request mailbox channel */
>> +	cl->dev = &pdev->dev;
>> +	cl->tx_done = ras2_tx_done;
>> +	cl->knows_txdone = true;
>> +	ras2_ctx->pcc_subspace_idx = *((int *)pdev->dev.platform_data);
>> +	dev_dbg(&pdev->dev, "pcc-subspace-id=%d\n", ras2_ctx-
>>pcc_subspace_idx);
>> +	ret = ras2_register_pcc_channel(ras2_ctx);
>
>In our enabling activities, we have found a challenge here.
>Our hardware has a single PCC channel corresponding to a single platform-wide
>scrub interface. This driver, following the ACPI spec, will create a new scrub
>node for each NUMA node. However, for us, this means that each scrub device
>will try to map the same PCC channel, and this causes an error.

Is failing to probe cleanly is enough for your platform?  i.e. put any error messages as dev_dbg()
or whichever one causes this problem.
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	ret = devm_add_action_or_reset(&pdev->dev, devm_ras2_release,
>ras2_ctx);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	if (ras2_is_patrol_scrub_support(ras2_ctx)) {
>> +		id = ida_alloc(&ras2_ida, GFP_KERNEL);
>> +		if (id < 0)
>> +			return id;
>> +		ras2_ctx->id = id;
>> +		snprintf(scrub_name, sizeof(scrub_name), "%s%d",
>RAS2_SCRUB, id);
>> +		dev_set_name(&pdev->dev, RAS2_ID_FORMAT, id);
>> +		hw_scrub_dev = devm_scrub_device_register(&pdev->dev,
>scrub_name,
>> +							  ras2_ctx,
>&ras2_scrub_ops,
>> +							  0, NULL);
>> +		if (PTR_ERR_OR_ZERO(hw_scrub_dev))
>> +			return PTR_ERR_OR_ZERO(hw_scrub_dev);
>> +	}
>> +	ras2_ctx->scrub_dev = hw_scrub_dev;
>> +
>> +	return 0;
>> +}
>
Thanks,
Shiju