Re: [PATCH v3 2/2] cxl/acpi: Use the ACPI CFMWS to create static decoder objects

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Wed, 16 Jun 2021 18:11:08 -0700
Alison Schofield <alison.schofield@intel.com> wrote:

> The ACPI CXL Early Discovery Table (CEDT) includes a list of CXL memory
> resources in CXL Fixed Memory Window Structures (CFMWS). Retrieve each
> CFMWS in the CEDT and add a cxl_decoder object to the root port (root0)
> for each memory resource.
> 
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
>  drivers/cxl/acpi.c | 119 +++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 119 insertions(+)
> 
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index 852b5c270464..018f5ac73b78 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -10,6 +10,123 @@
>  
>  static struct acpi_table_header *acpi_cedt;
>  
> +/* Encode defined in CXL 2.0 8.2.5.12.7 HDM Decoder Control Register */
> +#define CFMWS_INTERLEAVE_WAYS(x)	(1 << (x)->interleave_ways)
> +#define CFMWS_INTERLEAVE_GRANULARITY(x)	((x)->granularity + 8)
> +
> +static unsigned long cfmws_to_decoder_flags(int restrictions)
> +{
> +	unsigned long flags = 0;
> +
> +	if (restrictions & ACPI_CEDT_CFMWS_RESTRICT_TYPE2)
> +		flags |= CXL_DECODER_F_TYPE2;
> +	if (restrictions & ACPI_CEDT_CFMWS_RESTRICT_TYPE3)
> +		flags |= CXL_DECODER_F_TYPE3;
> +	if (restrictions & ACPI_CEDT_CFMWS_RESTRICT_VOLATILE)
> +		flags |= CXL_DECODER_F_RAM;
> +	if (restrictions & ACPI_CEDT_CFMWS_RESTRICT_PMEM)
> +		flags |= CXL_DECODER_F_PMEM;
> +	if (restrictions & ACPI_CEDT_CFMWS_RESTRICT_FIXED)
> +		flags |= CXL_DECODER_F_LOCK;
> +
> +	return flags;
> +}
> +
> +static int cxl_acpi_cfmws_verify(struct device *dev,
> +				 struct acpi_cedt_cfmws *cfmws)
> +{
> +	int expected_len;
> +
> +	if (cfmws->interleave_arithmetic != ACPI_CEDT_CFMWS_ARITHMETIC_MODULO) {
> +		dev_err(dev, "CFMWS Unsupported Interleave Arithmetic\n");
> +		return -EINVAL;
> +	}
> +
> +	if (!IS_ALIGNED(cfmws->base_hpa, SZ_256M)) {
> +		dev_err(dev, "CFMWS Base HPA not 256MB aligned\n");
> +		return -EINVAL;
> +	}
> +
> +	if (!IS_ALIGNED(cfmws->window_size, SZ_256M)) {
> +		dev_err(dev, "CFMWS Window Size not 256MB aligned\n");
> +		return -EINVAL;
> +	}
> +
> +	expected_len = struct_size((cfmws), interleave_targets,
> +				   CFMWS_INTERLEAVE_WAYS(cfmws));
> +
> +	if (cfmws->header.length < expected_len) {
> +		dev_err(dev, "CFMWS length %d less than expected %d\n",
> +			cfmws->header.length, expected_len);
> +		return -EINVAL;
> +	}
> +
> +	if (cfmws->header.length > expected_len)
> +		dev_dbg(dev, "CFMWS length %d greater than expected %d\n",
> +			cfmws->header.length, expected_len);
> +
> +	return 0;
> +}
> +
> +static void cxl_add_cfmws_decoders(struct device *dev,
> +				   struct cxl_port *root_port)
> +{
> +	struct acpi_cedt_cfmws *cfmws;
> +	struct cxl_decoder *cxld;
> +	acpi_size len, cur = 0;
> +	void *cedt_subtable;
> +	int rc;
> +
> +	len = acpi_cedt->length - sizeof(*acpi_cedt);
> +	cedt_subtable = acpi_cedt + 1;
> +
> +	while (cur < len) {
> +		struct acpi_cedt_header *c = cedt_subtable + cur;
> +
> +		if (c->type != ACPI_CEDT_TYPE_CFMWS) {
> +			cur += c->length;
> +			continue;
> +		}
> +
> +		cfmws = cedt_subtable + cur;
> +
> +		if (dev_WARN_ONCE(dev, cfmws->header.length < sizeof(*cfmws),
> +				  "CFMWS entry skipped: invalid length:%u\n",
> +				  cfmws->header.length)) {
> +			cur += c->length;
> +			continue;
> +		}
> +
> +		rc = cxl_acpi_cfmws_verify(dev, cfmws);
> +		if (rc) {
> +			dev_err(dev, "CFMWS range %#llx-%#llx not registered\n",
> +				cfmws->base_hpa, cfmws->base_hpa +
> +				cfmws->window_size - 1);
> +			cur += c->length;
> +			continue;
> +		}
> +
> +		cxld = devm_cxl_add_decoder(dev, root_port,
> +				CFMWS_INTERLEAVE_WAYS(cfmws),
> +				cfmws->base_hpa, cfmws->window_size,
> +				CFMWS_INTERLEAVE_WAYS(cfmws),
> +				CFMWS_INTERLEAVE_GRANULARITY(cfmws),
> +				CXL_DECODER_EXPANDER,
> +				cfmws_to_decoder_flags(cfmws->restrictions));
> +
> +		if (IS_ERR(cxld)) {
> +			dev_err(dev, "Failed to add decoder for %#llx-%#llx\n",
> +				cfmws->base_hpa, cfmws->base_hpa +
> +				cfmws->window_size - 1);

This sounds rather fatal... I guess it'll be exposed later as we won't have
any means of using the decoder so we don't have to error out here though.

> +		} else {
> +			dev_dbg(dev, "add: %s range %#llx-%#llx\n",
> +				dev_name(&cxld->dev), cfmws->base_hpa,
> +				 cfmws->base_hpa + cfmws->window_size - 1);
> +		}
> +		cur += c->length;
> +	}
> +}
> +
>  static struct acpi_cedt_chbs *cxl_acpi_match_chbs(struct device *dev, u32 uid)
>  {
>  	struct acpi_cedt_chbs *chbs, *chbs_match = NULL;
> @@ -271,6 +388,8 @@ static int cxl_acpi_probe(struct platform_device *pdev)
>  	if (rc)
>  		goto out;
>  
> +	cxl_add_cfmws_decoders(host, root_port);
> +
>  	/*
>  	 * Root level scanned with host-bridge as dports, now scan host-bridges
>  	 * for their role as CXL uports to their CXL-capable PCIe Root Ports.