reset: ath79: fix reset sequence for AR9344

According to datasheet, on AR9344 the switch and switch analog need to
be reset first before initiating a full reset.

This fixes sporadic reboot issues. Instead of rebooting, the device will
just hang. Without this patch, I had failed resets after 5, 20 and 250
tries. With this patch I have more than 2200 successful resets.

Other chips like AR7100 do not have this specific requirement in the
datasheet and also the meaning for bits 8 and 12 is slightly different,
so only perform this sequence on AR9344.

Signed-off-by: Nico Boehr <github-ffs@nicoboehr.de>

patches/openwrt/0006-reset-ath79-fix-reset-sequence-for-AR9344.patch

+From: Nico <github@nicoboehr.de>
+Date: Mon, 16 Dec 2024 22:19:01 +0000
+Subject: reset: ath79: fix reset sequence for AR9344
+
+According to datasheet, on AR9344 the switch and switch analog need to
+be reset first before initiating a full reset.
+
+This fixes sporadic reboot issues. Instead of rebooting, the device will
+just hang. Without this patch, I had failed resets after 5, 20 and 250
+tries. With this patch I have more than 2200 successful resets.
+
+Other chips like AR7100 do not have this specific requirement in the
+datasheet and also the meaning for bits 8 and 12 is slightly different,
+so only perform this sequence on AR9344.
+
+diff --git a/target/linux/ath79/patches-6.6/940-ath79-fix-reset-sequence.patch b/target/linux/ath79/patches-6.6/940-ath79-fix-reset-sequence.patch
+new file mode 100644
+index 0000000000000000000000000000000000000000..dccb8449e9cc03701495afcbc4196540d0b1c15d
+--- /dev/null
++++ b/target/linux/ath79/patches-6.6/940-ath79-fix-reset-sequence.patch
+@@ -0,0 +1,71 @@
++--- a/drivers/reset/reset-ath79.c
+++++ b/drivers/reset/reset-ath79.c
++@@ -12,6 +12,8 @@
++ #include <linux/platform_device.h>
++ #include <linux/reset-controller.h>
++ #include <linux/reboot.h>
+++#include <linux/delay.h>
+++#include <linux/of.h>
++ 
++ struct ath79_reset {
++ 	struct reset_controller_dev rcdev;
++@@ -21,16 +23,13 @@ struct ath79_reset {
++ };
++ 
++ #define FULL_CHIP_RESET 24
+++#define ETH_SWITCH_RESET 8
+++#define ETH_SWITCH_ARESET 12
++ 
++-static int ath79_reset_update(struct reset_controller_dev *rcdev,
+++static void __ath79_reset_update_unlocked(struct ath79_reset *ath79_reset,
++ 			unsigned long id, bool assert)
++ {
++-	struct ath79_reset *ath79_reset =
++-		container_of(rcdev, struct ath79_reset, rcdev);
++-	unsigned long flags;
++ 	u32 val;
++-
++-	spin_lock_irqsave(&ath79_reset->lock, flags);
++ 	val = readl(ath79_reset->base);
++ 	if (assert)
++ 		val |= BIT(id);
++@@ -39,6 +38,17 @@ static int ath79_reset_update(struct res
++ 	writel(val, ath79_reset->base);
++ 	/* Flush cache */
++ 	readl(ath79_reset->base);
+++}
+++
+++static int ath79_reset_update(struct reset_controller_dev *rcdev,
+++			unsigned long id, bool assert)
+++{
+++	struct ath79_reset *ath79_reset =
+++		container_of(rcdev, struct ath79_reset, rcdev);
+++	unsigned long flags;
+++
+++	spin_lock_irqsave(&ath79_reset->lock, flags);
+++	__ath79_reset_update_unlocked(ath79_reset, id, assert);
++ 	spin_unlock_irqrestore(&ath79_reset->lock, flags);
++ 
++ 	return 0;
++@@ -79,8 +89,20 @@ static int ath79_reset_restart_handler(s
++ {
++ 	struct ath79_reset *ath79_reset =
++ 		container_of(nb, struct ath79_reset, restart_nb);
+++	unsigned long flags;
++ 
++-	ath79_reset_assert(&ath79_reset->rcdev, FULL_CHIP_RESET);
+++	spin_lock_irqsave(&ath79_reset->lock, flags);
+++	/* special reset sequence required for AR9344 - see datasheet p 111 */
+++	if (of_machine_is_compatible("qca,ar9344")) {
+++		__ath79_reset_update_unlocked(ath79_reset, ETH_SWITCH_RESET, true);
+++		mdelay(2);
+++		__ath79_reset_update_unlocked(ath79_reset, ETH_SWITCH_ARESET, true);
+++		mdelay(2);
+++		__ath79_reset_update_unlocked(ath79_reset, FULL_CHIP_RESET, true);
+++		mdelay(10);
+++	} else
+++		__ath79_reset_update_unlocked(ath79_reset, FULL_CHIP_RESET, true);
+++	spin_unlock_irqrestore(&ath79_reset->lock, flags);
++ 
++ 	return NOTIFY_DONE;
++ }