wil6210: fix random failure to bring network interface up

Currently when we want to bring the interface up, we first
reset the device which causes the boot loader to run. Then
we halt the device CPU, load FW image and resume the device
CPU.
There are some boot loader versions which perform redundant
memory accesses even when idle. Halting the device CPU
while boot loader access memory can cause the device memory
controller to get stuck, the FW will fail to load and the
network interface will not come up.
For such boot loaders implement a workaround where we freeze
the boot loader before halting the device CPU, so it will not
perform any memory accesses.

Signed-off-by: Lior David <liord@codeaurora.org>
Signed-off-by: Maya Erez <merez@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

1 files changed, 101 insertions, 1 deletions

diff --git a/drivers/net/wireless/ath/wil6210/main.c b/drivers/net/wireless/ath/wil6210/main.c
index d95ff742e386..575aafe149a6 100644
--- a/drivers/net/wireless/ath/wil6210/main.c
+++ b/drivers/net/wireless/ath/wil6210/main.c
@@ -638,6 +638,98 @@ void wil_priv_deinit(struct wil6210_priv *wil)
 	destroy_workqueue(wil->wmi_wq);
 }
 
+static void wil_shutdown_bl(struct wil6210_priv *wil)
+{
+	u32 val;
+
+	wil_s(wil, RGF_USER_BL +
+	      offsetof(struct bl_dedicated_registers_v1,
+		       bl_shutdown_handshake), BL_SHUTDOWN_HS_GRTD);
+
+	usleep_range(100, 150);
+
+	val = wil_r(wil, RGF_USER_BL +
+		    offsetof(struct bl_dedicated_registers_v1,
+			     bl_shutdown_handshake));
+	if (val & BL_SHUTDOWN_HS_RTD) {
+		wil_dbg_misc(wil, "BL is ready for halt\n");
+		return;
+	}
+
+	wil_err(wil, "BL did not report ready for halt\n");
+}
+
+/* this format is used by ARC embedded CPU for instruction memory */
+static inline u32 ARC_me_imm32(u32 d)
+{
+	return ((d & 0xffff0000) >> 16) | ((d & 0x0000ffff) << 16);
+}
+
+/* defines access to interrupt vectors for wil_freeze_bl */
+#define ARC_IRQ_VECTOR_OFFSET(N)	((N) * 8)
+/* ARC long jump instruction */
+#define ARC_JAL_INST			(0x20200f80)
+
+static void wil_freeze_bl(struct wil6210_priv *wil)
+{
+	u32 jal, upc, saved;
+	u32 ivt3 = ARC_IRQ_VECTOR_OFFSET(3);
+
+	jal = wil_r(wil, wil->iccm_base + ivt3);
+	if (jal != ARC_me_imm32(ARC_JAL_INST)) {
+		wil_dbg_misc(wil, "invalid IVT entry found, skipping\n");
+		return;
+	}
+
+	/* prevent the target from entering deep sleep
+	 * and disabling memory access
+	 */
+	saved = wil_r(wil, RGF_USER_USAGE_8);
+	wil_w(wil, RGF_USER_USAGE_8, saved | BIT_USER_PREVENT_DEEP_SLEEP);
+	usleep_range(20, 25); /* let the BL process the bit */
+
+	/* redirect to endless loop in the INT_L1 context and let it trap */
+	wil_w(wil, wil->iccm_base + ivt3 + 4, ARC_me_imm32(ivt3));
+	usleep_range(20, 25); /* let the BL get into the trap */
+
+	/* verify the BL is frozen */
+	upc = wil_r(wil, RGF_USER_CPU_PC);
+	if (upc < ivt3 || (upc > (ivt3 + 8)))
+		wil_dbg_misc(wil, "BL freeze failed, PC=0x%08X\n", upc);
+
+	wil_w(wil, RGF_USER_USAGE_8, saved);
+}
+
+static void wil_bl_prepare_halt(struct wil6210_priv *wil)
+{
+	u32 tmp, ver;
+
+	/* before halting device CPU driver must make sure BL is not accessing
+	 * host memory. This is done differently depending on BL version:
+	 * 1. For very old BL versions the procedure is skipped
+	 * (not supported).
+	 * 2. For old BL version we use a special trick to freeze the BL
+	 * 3. For new BL versions we shutdown the BL using handshake procedure.
+	 */
+	tmp = wil_r(wil, RGF_USER_BL +
+		    offsetof(struct bl_dedicated_registers_v0,
+			     boot_loader_struct_version));
+	if (!tmp) {
+		wil_dbg_misc(wil, "old BL, skipping halt preperation\n");
+		return;
+	}
+
+	tmp = wil_r(wil, RGF_USER_BL +
+		    offsetof(struct bl_dedicated_registers_v1,
+			     bl_shutdown_handshake));
+	ver = BL_SHUTDOWN_HS_PROT_VER(tmp);
+
+	if (ver > 0)
+		wil_shutdown_bl(wil);
+	else
+		wil_freeze_bl(wil);
+}
+
 static inline void wil_halt_cpu(struct wil6210_priv *wil)
 {
 	wil_w(wil, RGF_USER_USER_CPU_0, BIT_USER_USER_CPU_MAN_RST);
@@ -685,11 +777,16 @@ static int wil_target_reset(struct wil6210_priv *wil, int no_flash)
 
 	wil_halt_cpu(wil);
 
-	if (!no_flash)
+	if (!no_flash) {
 		/* clear all boot loader "ready" bits */
 		wil_w(wil, RGF_USER_BL +
 		      offsetof(struct bl_dedicated_registers_v0,
 			       boot_loader_ready), 0);
+		/* this should be safe to write even with old BLs */
+		wil_w(wil, RGF_USER_BL +
+		      offsetof(struct bl_dedicated_registers_v1,
+			       bl_shutdown_handshake), 0);
+	}
 	/* Clear Fw Download notification */
 	wil_c(wil, RGF_USER_USAGE_6, BIT(0));
 
@@ -1156,6 +1253,9 @@ int wil_reset(struct wil6210_priv *wil, bool load_fw)
 		wil_info(wil, "Use firmware <%s> + board <%s>\n",
 			 wil->wil_fw_name, WIL_BOARD_FILE_NAME);
 
+		if (!no_flash)
+			wil_bl_prepare_halt(wil);
+
 		wil_halt_cpu(wil);
 		memset(wil->fw_version, 0, sizeof(wil->fw_version));
 		/* Loading f/w from the file */