cxl/acpi: Make the XOR calculations available for testing

In preparation for adding a test module that can exercise the address
translation functions performed by the CXL Driver, refactor the XOR
implementation like this:

- Extract the core calculation into a standalone helper function,
- Export the new function for use by test module cxl_translate only,
- Enhance the parameter validation since this new function will be
  called from a test module with no guarantee of valid parameters,
- Move the define of struct cxl_cxims_data to cxl.h so the test module
  can build xormaps.

Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

2 files changed, 43 insertions, 11 deletions

diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
index bd2e282ca93a..a8069278cb56 100644
--- a/drivers/cxl/acpi.c
+++ b/drivers/cxl/acpi.c
@@ -11,25 +11,36 @@
 #include "cxlpci.h"
 #include "cxl.h"
 
-struct cxl_cxims_data {
-	int nr_maps;
-	u64 xormaps[] __counted_by(nr_maps);
-};
-
 static const guid_t acpi_cxl_qtg_id_guid =
 	GUID_INIT(0xF365F9A6, 0xA7DE, 0x4071,
 		  0xA6, 0x6A, 0xB4, 0x0C, 0x0B, 0x4F, 0x8E, 0x52);
 
-static u64 cxl_apply_xor_maps(struct cxl_root_decoder *cxlrd, u64 addr)
+#define HBIW_TO_NR_MAPS_SIZE (CXL_DECODER_MAX_INTERLEAVE + 1)
+static const int hbiw_to_nr_maps[HBIW_TO_NR_MAPS_SIZE] = {
+	[1] = 0, [2] = 1, [3] = 0, [4] = 2, [6] = 1, [8] = 3, [12] = 2, [16] = 4
+};
+
+static const int valid_hbiw[] = { 1, 2, 3, 4, 6, 8, 12, 16 };
+
+u64 cxl_do_xormap_calc(struct cxl_cxims_data *cximsd, u64 addr, int hbiw)
 {
-	struct cxl_cxims_data *cximsd = cxlrd->platform_data;
-	int hbiw = cxlrd->cxlsd.nr_targets;
+	int nr_maps_to_apply = -1;
 	u64 val;
 	int pos;
 
-	/* No xormaps for host bridge interleave ways of 1 or 3 */
-	if (hbiw == 1 || hbiw == 3)
-		return addr;
+	/*
+	 * Strictly validate hbiw since this function is used for testing and
+	 * that nullifies any expectation of trusted parameters from the CXL
+	 * Region Driver.
+	 */
+	for (int i = 0; i < ARRAY_SIZE(valid_hbiw); i++) {
+		if (valid_hbiw[i] == hbiw) {
+			nr_maps_to_apply = hbiw_to_nr_maps[hbiw];
+			break;
+		}
+	}
+	if (nr_maps_to_apply == -1 || nr_maps_to_apply > cximsd->nr_maps)
+		return ULLONG_MAX;
 
 	/*
 	 * In regions using XOR interleave arithmetic the CXL HPA may not
@@ -60,6 +71,14 @@ static u64 cxl_apply_xor_maps(struct cxl_root_decoder *cxlrd, u64 addr)
 
 	return addr;
 }
+EXPORT_SYMBOL_FOR_MODULES(cxl_do_xormap_calc, "cxl_translate");
+
+static u64 cxl_apply_xor_maps(struct cxl_root_decoder *cxlrd, u64 addr)
+{
+	struct cxl_cxims_data *cximsd = cxlrd->platform_data;
+
+	return cxl_do_xormap_calc(cximsd, addr, cxlrd->cxlsd.nr_targets);
+}
 
 struct cxl_cxims_context {
 	struct device *dev;
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 10bee9aaa943..e8931b626fc6 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -743,6 +743,19 @@ int cxl_validate_translation_params(u8 eiw, u16 eig, int pos);
 u64 cxl_calculate_hpa_offset(u64 dpa_offset, int pos, u8 eiw, u16 eig);
 u64 cxl_calculate_dpa_offset(u64 hpa_offset, u8 eiw, u16 eig);
 int cxl_calculate_position(u64 hpa_offset, u8 eiw, u16 eig);
+struct cxl_cxims_data {
+	int nr_maps;
+	u64 xormaps[] __counted_by(nr_maps);
+};
+
+#if IS_ENABLED(CONFIG_CXL_ACPI)
+u64 cxl_do_xormap_calc(struct cxl_cxims_data *cximsd, u64 addr, int hbiw);
+#else
+static inline u64 cxl_do_xormap_calc(struct cxl_cxims_data *cximsd, u64 addr, int hbiw)
+{
+	return ULLONG_MAX;
+}
+#endif
 
 int cxl_num_decoders_committed(struct cxl_port *port);
 bool is_cxl_port(const struct device *dev);