bus: rifsc: fix RIF configuration check for peripherals

Peripheral holding CID0 cannot be accessed, remove this completely
incorrect check. While there, fix  and simplify the semaphore checking
that should be performed when the CID filtering is enabled.

Fixes: a182084 ("bus: rifsc: introduce RIFSC firewall controller driver")
Signed-off-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
Link: https://lore.kernel.org/r/20260129-fix_cid_check_rifsc-v1-1-ef280ccf764d@foss.st.com
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>

Author: GseoC

drivers/bus/stm32_rifsc.c

@@ -687,54 +687,38 @@ static int stm32_rifsc_grant_access(struct stm32_firewall_controller *ctrl, u32
 	sec_reg_value = readl(rifsc_controller->mmio + RIFSC_RISC_SECCFGR0 + 0x4 * reg_id);
 	cid_reg_value = readl(rifsc_controller->mmio + RIFSC_RISC_PER0_CIDCFGR + 0x8 * firewall_id);
 
-	/* First check conditions for semaphore mode, which doesn't take into account static CID. */
-	if ((cid_reg_value & CIDCFGR_SEMEN) && (cid_reg_value & CIDCFGR_CFEN)) {
-		if (cid_reg_value & BIT(RIF_CID1 + SEMWL_SHIFT)) {
-			/* Static CID is irrelevant if semaphore mode */
-			goto skip_cid_check;
-		} else {
-			dev_dbg(rifsc_controller->dev,
-				"Invalid bus semaphore configuration: index %d\n", firewall_id);
-			return -EACCES;
-		}
-	}
-
-	/*
-	 * Skip CID check if CID filtering isn't enabled or filtering is enabled on CID0, which
-	 * corresponds to whatever CID.
-	 */
-	if (!(cid_reg_value & CIDCFGR_CFEN) ||
-	    FIELD_GET(RIFSC_RISC_SCID_MASK, cid_reg_value) == RIF_CID0)
-		goto skip_cid_check;
-
-	/* Coherency check with the CID configuration */
-	if (FIELD_GET(RIFSC_RISC_SCID_MASK, cid_reg_value) != RIF_CID1) {
-		dev_dbg(rifsc_controller->dev, "Invalid CID configuration for peripheral: %d\n",
-			firewall_id);
-		return -EACCES;
-	}
-
-skip_cid_check:
 	/* Check security configuration */
 	if (sec_reg_value & BIT(reg_offset)) {
 		dev_dbg(rifsc_controller->dev,
 			"Invalid security configuration for peripheral: %d\n", firewall_id);
 		return -EACCES;
 	}
 
-	/*
-	 * If the peripheral is in semaphore mode, take the semaphore so that
-	 * the CID1 has the ownership.
-	 */
-	if ((cid_reg_value & CIDCFGR_SEMEN) && (cid_reg_value & CIDCFGR_CFEN)) {
+	/* Skip CID check if CID filtering isn't enabled */
+	if (!(cid_reg_value & CIDCFGR_CFEN))
+		goto skip_cid_check;
+
+	/* First check conditions for semaphore mode, which doesn't take into account static CID. */
+	if (cid_reg_value & CIDCFGR_SEMEN) {
+		if (!(cid_reg_value & BIT(RIF_CID1 + SEMWL_SHIFT))) {
+			dev_dbg(rifsc_controller->dev,
+				"Invalid bus semaphore configuration: index %d\n", firewall_id);
+			return -EACCES;
+		}
+
 		rc = stm32_rif_acquire_semaphore(rifsc_controller, firewall_id);
 		if (rc) {
-			dev_err(rifsc_controller->dev,
+			dev_dbg(rifsc_controller->dev,
 				"Couldn't acquire semaphore for peripheral: %d\n", firewall_id);
 			return rc;
 		}
+	} else if (FIELD_GET(RIFSC_RISC_SCID_MASK, cid_reg_value) != RIF_CID1) {
+		dev_dbg(rifsc_controller->dev, "Invalid CID configuration for peripheral: %d\n",
+			firewall_id);
+		return -EACCES;
 	}
 
+skip_cid_check:
 	return 0;
 }