iwlwifi: pcie: set LTR to avoid completion timeout

On some platforms, the preset values aren't correct and then we may
get a completion timeout in the firmware. Change the LTR configuration
to avoid that. The firmware will do some more complex reinit of this
later, but for the boot process we use ~250usec.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/iwlwifi.20201107104557.d83d591c05ba.I42885c9fb500bc08b9a4c07c4ff3d436cc7a3c84@changeid

drivers/net/wireless/intel/iwlwifi/iwl-csr.h

@@ -147,6 +147,16 @@
 #define CSR_MAC_SHADOW_REG_CTL2		(CSR_BASE + 0x0AC)
 #define CSR_MAC_SHADOW_REG_CTL2_RX_WAKE	0xFFFF
 
+/* LTR control (since IWL_DEVICE_FAMILY_22000) */
+#define CSR_LTR_LONG_VAL_AD			(CSR_BASE + 0x0D4)
+#define CSR_LTR_LONG_VAL_AD_NO_SNOOP_REQ	0x80000000
+#define CSR_LTR_LONG_VAL_AD_NO_SNOOP_SCALE	0x1c000000
+#define CSR_LTR_LONG_VAL_AD_NO_SNOOP_VAL	0x03ff0000
+#define CSR_LTR_LONG_VAL_AD_SNOOP_REQ		0x00008000
+#define CSR_LTR_LONG_VAL_AD_SNOOP_SCALE		0x00001c00
+#define CSR_LTR_LONG_VAL_AD_SNOOP_VAL		0x000003ff
+#define CSR_LTR_LONG_VAL_AD_SCALE_USEC		2
+
 /* GIO Chicken Bits (PCI Express bus link power management) */
 #define CSR_GIO_CHICKEN_BITS    (CSR_BASE+0x100)
 

drivers/net/wireless/intel/iwlwifi/pcie/ctxt-info-gen3.c

@@ -252,6 +252,26 @@ int iwl_pcie_ctxt_info_gen3_init(struct iwl_trans *trans,
 
 	iwl_set_bit(trans, CSR_CTXT_INFO_BOOT_CTRL,
 		    CSR_AUTO_FUNC_BOOT_ENA);
+
+	if (trans->trans_cfg->device_family == IWL_DEVICE_FAMILY_AX210) {
+		/*
+		 * The firmware initializes this again later (to a smaller
+		 * value), but for the boot process initialize the LTR to
+		 * ~250 usec.
+		 */
+		u32 val = CSR_LTR_LONG_VAL_AD_NO_SNOOP_REQ |
+			  u32_encode_bits(CSR_LTR_LONG_VAL_AD_SCALE_USEC,
+					  CSR_LTR_LONG_VAL_AD_NO_SNOOP_SCALE) |
+			  u32_encode_bits(250,
+					  CSR_LTR_LONG_VAL_AD_NO_SNOOP_VAL) |
+			  CSR_LTR_LONG_VAL_AD_SNOOP_REQ |
+			  u32_encode_bits(CSR_LTR_LONG_VAL_AD_SCALE_USEC,
+					  CSR_LTR_LONG_VAL_AD_SNOOP_SCALE) |
+			  u32_encode_bits(250, CSR_LTR_LONG_VAL_AD_SNOOP_VAL);
+
+		iwl_write32(trans, CSR_LTR_LONG_VAL_AD, val);
+	}
+
 	if (trans->trans_cfg->device_family >= IWL_DEVICE_FAMILY_AX210)
 		iwl_write_umac_prph(trans, UREG_CPU_INIT_RUN, 1);
 	else