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Date:   Wed, 16 Jun 2021 09:17:40 -0700
From:   Ben Widawsky <ben.widawsky@intel.com>
To:     Alison Schofield <alison.schofield@intel.com>
Cc:     Dan Williams <dan.j.williams@intel.com>,
        Ira Weiny <ira.weiny@intel.com>,
        Vishal Verma <vishal.l.verma@intel.com>,
        linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org,
        Linux ACPI <linux-acpi@vger.kernel.org>
Subject: Re: [PATCH v2 2/2] cxl/acpi: Use the ACPI CFMWS to create static
 decoder objects
Message-ID: <20210616161740.k4nxeh3bmem56gwa@intel.com>
References: <cover.1623800340.git.alison.schofield@intel.com>
 <48f1b59105e46f04b38347fc1555bb5c8d654cff.1623800340.git.alison.schofield@intel.com>
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In-Reply-To: <48f1b59105e46f04b38347fc1555bb5c8d654cff.1623800340.git.alison.schofield@intel.com>
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On 21-06-15 17:20:39, Alison Schofield 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>
> ---
>  drivers/cxl/acpi.c | 114 +++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 114 insertions(+)
> 
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index b6d9cd45428c..e3aa356d4dcd 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -8,8 +8,120 @@
>  #include <linux/pci.h>
>  #include "cxl.h"
>  
> +/* 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 struct acpi_table_header *cedt_table;
>  
> +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;
> +}

I know these flags aren't introduced by this patch, but I'm wondering if it
makes sense to not just use the spec definitions rather than defining our own.
It doesn't do much harm, but it's extra typing everytime the spec adds new flags
and I don't really see the upside.

> +
> +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 (expected_len != cfmws->header.length) {

I'd switch this to:
if (expected_len < cfmws->header.length)

If it's too big, just print a dev_dbg.

> +		dev_err(dev, "CFMWS interleave ways and targets mismatch\n");
> +		return -EINVAL;
> +	}
> +
> +	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_base;
> +	int rc;
> +
> +	len = cedt_table->length - sizeof(*cedt_table);
> +	cedt_base = cedt_table + 1;

naming suggestions per previous patch... up to you though.

> +
> +	while (cur < len) {
> +		struct acpi_cedt_header *c = cedt_base + cur;
> +
> +		if (c->type != ACPI_CEDT_TYPE_CFMWS) {
> +			cur += c->length;
> +			continue;
> +		}
> +
> +		cfmws = cedt_base + cur;
> +
> +		if (cfmws->header.length < sizeof(*cfmws)) {
> +			dev_err(dev, "Invalid CFMWS header length %u\n",
> +				cfmws->header.length);
> +			dev_err(dev, "Failed to add decoders\n");
> +			return;
> +		}
> +
> +		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),

Interesting... this made me question, how can we have a different number of
targets and ways?

> +				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);
> +		} 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;
> @@ -251,6 +363,8 @@ 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.
> -- 
> 2.26.2
>