[PATCH 3/4] cxl/acpi: Move the target entry(n) calc to its own function

[alison.schofield@intel.com]

From: Alison Schofield <alison.schofield@intel.com>

In preparation for reusing the calculation of a targets
entry (n) in the host bridge interleave set, move it to
a separate function.

Make it accept an HPA parameter so that it is useful for
validating DPA to HPA address translations.

No functional change.

Signed-off-by: Alison Schofield <alison.schofield@intel.com>
---
 drivers/cxl/acpi.c | 41 +++++++++++++++++++++++------------------
 1 file changed, 23 insertions(+), 18 deletions(-)

diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
index 98c84942ed37..38b5f77164b0 100644
--- a/drivers/cxl/acpi.c
+++ b/drivers/cxl/acpi.c
@@ -19,6 +19,25 @@ struct cxl_cxims_data {
  * Find a targets entry (n) in the host bridge interleave list.
  * CXL Specfication 3.0 Table 9-22
  */
+static int cxl_xor_calc_n(u64 hpa, struct cxl_cxims_data *cximsd, int iw,
+			  int ig)
+{
+	int eiw, i = 0, n = 0;
+
+	/* IW: 2,4,6,8,12,16 begin building 'n' using xormaps */
+	if (iw != 3) {
+		for (i = 0; i < cximsd->nr_maps; i++)
+			n |= (hweight64(hpa & cximsd->xormaps[i]) & 1) << i;
+	}
+	/* IW: 3,6,12 add a modulo calculation to 'n' */
+	if (!is_power_of_2(iw)) {
+		eiw = ilog2(iw / 3) + 8;
+		hpa &= GENMASK_ULL(51, eiw + ig);
+		n |= do_div(hpa, 3) << i;
+	}
+	return n;
+}
+
 static struct cxl_dport *cxl_hb_xor(struct cxl_root_decoder *cxlrd, int pos)
 {
 	struct cxl_cxims_data *cximsd = cxlrd->platform_data;
@@ -26,7 +45,7 @@ static struct cxl_dport *cxl_hb_xor(struct cxl_root_decoder *cxlrd, int pos)
 	struct cxl_decoder *cxld = &cxlsd->cxld;
 	int ig = cxld->interleave_granularity;
 	int iw = cxld->interleave_ways;
-	int eiw, i = 0, n = 0;
+	int n = 0;
 	u64 hpa;
 
 	if (dev_WARN_ONCE(&cxld->dev,
@@ -34,26 +53,12 @@ static struct cxl_dport *cxl_hb_xor(struct cxl_root_decoder *cxlrd, int pos)
 			  "misconfigured root decoder\n"))
 		return NULL;
 
-	if (iw == 1)
-		/* Entry is always 0 for no interleave */
-		return cxlrd->cxlsd.target[0];
-
 	hpa = cxlrd->res->start + pos * ig;
 
-	if (iw == 3)
-		goto no_map;
+	/* Entry (n) is 0 for no interleave (iw == 1) */
+	if (iw != 1)
+		n = cxl_xor_calc_n(hpa, cximsd, iw, ig);
 
-	/* IW: 2,4,6,8,12,16 begin building 'n' using xormaps */
-	for (i = 0; i < cximsd->nr_maps; i++)
-		n |= (hweight64(hpa & cximsd->xormaps[i]) & 1) << i;
-
-no_map:
-	/* IW: 3,6,12 add a modulo calculation to 'n' */
-	if (!is_power_of_2(iw)) {
-		eiw = ilog2(iw / 3) + 8;
-		hpa &= GENMASK_ULL(51, eiw + ig);
-		n |= do_div(hpa, 3) << i;
-	}
 	return cxlrd->cxlsd.target[n];
 }
 
-- 
2.37.3