wifi: rtlwifi: rtl8821ae: Use pci_find_capability()

Instead of open coding the capability structure search, find the PM
Capability using pci_find_capability().

While at it, rename the generic 'cap_pointer' to 'pm_cap' which makes
the intent of the code more obvious.
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20231124084725.12738-7-ilpo.jarvinen@linux.intel.com

drivers/net/wireless/realtek/rtlwifi/rtl8821ae/hw.c

@@ -2270,42 +2270,11 @@ static void _rtl8821ae_clear_pci_pme_status(struct ieee80211_hw *hw)
 {
 	struct rtl_priv *rtlpriv = rtl_priv(hw);
 	struct rtl_pci *rtlpci = rtl_pcidev(rtl_pcipriv(hw));
-	u16 cap_hdr;
-	u8 cap_pointer;
-	u8 cap_id = 0xff;
 	u8 pmcs_reg;
-	u8 cnt = 0;
+	u8 pm_cap;
 
-	/* Get the Capability pointer first,
-	 * the Capability Pointer is located at
-	 * offset 0x34 from the Function Header */
-
-	pci_read_config_byte(rtlpci->pdev, 0x34, &cap_pointer);
-	rtl_dbg(rtlpriv, COMP_INIT, DBG_LOUD,
-		"PCI configuration 0x34 = 0x%2x\n", cap_pointer);
-
-	do {
-		pci_read_config_word(rtlpci->pdev, cap_pointer, &cap_hdr);
-		cap_id = cap_hdr & 0xFF;
-
-		rtl_dbg(rtlpriv, COMP_INIT, DBG_LOUD,
-			"in pci configuration, cap_pointer%x = %x\n",
-			cap_pointer, cap_id);
-
-		if (cap_id == 0x01) {
-			break;
-		} else {
-			/* point to next Capability */
-			cap_pointer = (cap_hdr >> 8) & 0xFF;
-			/* 0: end of pci capability, 0xff: invalid value */
-			if (cap_pointer == 0x00 || cap_pointer == 0xff) {
-				cap_id = 0xff;
-				break;
-			}
-		}
-	} while (cnt++ < 200);
-
-	if (cap_id != 0x01) {
+	pm_cap = pci_find_capability(rtlpci->pdev, PCI_CAP_ID_PM);
+	if (!pm_cap) {
 		rtl_dbg(rtlpriv, COMP_INIT, DBG_WARNING,
 			"Cannot find PME Capability\n");
 		return;
@@ -2314,22 +2283,20 @@ static void _rtl8821ae_clear_pci_pme_status(struct ieee80211_hw *hw)
 	/* Get the PM CSR (Control/Status Register),
 	 * The PME_Status is located at PM Capatibility offset 5, bit 7
 	 */
-	pci_read_config_byte(rtlpci->pdev, cap_pointer + 5, &pmcs_reg);
+	pci_read_config_byte(rtlpci->pdev, pm_cap + 5, &pmcs_reg);
 
 	if (pmcs_reg & BIT(7)) {
 		/* Clear PME_Status with write */
-		pci_write_config_byte(rtlpci->pdev, cap_pointer + 5,
-				      pmcs_reg);
+		pci_write_config_byte(rtlpci->pdev, pm_cap + 5, pmcs_reg);
 		/* Read it back to check */
-		pci_read_config_byte(rtlpci->pdev, cap_pointer + 5,
-				     &pmcs_reg);
+		pci_read_config_byte(rtlpci->pdev, pm_cap + 5, &pmcs_reg);
 		rtl_dbg(rtlpriv, COMP_INIT, DBG_DMESG,
 			"Clear PME status 0x%2x to 0x%2x\n",
-			cap_pointer + 5, pmcs_reg);
+			pm_cap + 5, pmcs_reg);
 	} else {
 		rtl_dbg(rtlpriv, COMP_INIT, DBG_DMESG,
 			"PME status(0x%2x) = 0x%2x\n",
-			cap_pointer + 5, pmcs_reg);
+			pm_cap + 5, pmcs_reg);
 	}
 }