Re: [RFC PATCH v7 10/12] ACPI:RAS2: Add common library for RAS2 PCC interfaces

[Daniel Ferguson <danielf@os.amperecomputing.com>]

> +static int ras2_check_pcc_chan(struct ras2_context *ras2_ctx)
> +{
> +	struct acpi_ras2_shared_memory  __iomem *generic_comm_base = ras2_ctx->pcc_comm_addr;
> +	ktime_t next_deadline = ktime_add(ktime_get(), ras2_ctx->deadline);
> +
> +	while (!ktime_after(ktime_get(), next_deadline)) {
> +		/*
> +		 * As per ACPI spec, the PCC space wil be initialized by
> +		 * platform and should have set the command completion bit when
> +		 * PCC can be used by OSPM
> +		 */
> +		if (readw_relaxed(&generic_comm_base->status) & RAS2_PCC_CMD_COMPLETE)
> +			return 0;

We should consider adding error checking here. In a modification of this
driver in our enabling efforts, we are checking bit 2 in the status register
for errors. For example, in our FW, we will set bit 2 if you try to 
disable an
already disabled scrub.
> +		/*
> +		 * Reducing the bus traffic in case this loop takes longer than
> +		 * a few retries.
> +		 */
> +		udelay(10);
> +	}
> +
> +	return -EIO;
> +}