[PATCH 2/2] platform: generic: eswin: Add eic770x_hsm and fix warm reset issues

[Bo Gan <ganboing@gmail.com>]

During warm reset, my EIC770X/Hifive Premier P550 can sometimes
encounter memory corruption issue crashing Linux boot. Currently the
issue is mitigated by having a sbi_printf before writing to the reset
register. I analyzed the issue further since then. From the SoC
datasheet[1], it's recommended to implement power-down flow as:

  a. Designate a primary core, and let it broadcast requests to other
     cores to execute a CEASE insn. Primary core also notifies an
     "Externel Agent" to start monitoring.
  b. Primary core waits for other cores to CEASE before it CEASEs.
  c. "External Agent" waits for primary core to CEASE before resets
     the Core Complex.

It's possible that EIC770X can trigger undefined behavior if the core
complex is reset while the harts are actively running. The sbi_printf
in the reset handler effectively hides the problem by delaying the
reset -- by the time sbi_printf finishes, all other harts will have
already landed in the loop in sbi_hsm_hart_wait(), which parks the hart.
Without the sbi_printf, I confirmed that other harts haven't reached
sbi_hsm_hart_wait yet before current hart resets the SoC. (by debugging)

To safely reset, and inspired by the datasheet, the warm reset logic
in eic770x.c now use the current hart as both primary core and the
"External Agent", and other harts as secondary cores. It leverages
the HSM framework and a new eic770x_hsm device to CEASE other harts,
and wait for them to CEASE before resets the SoC. with the sbi_printf
before reset removed, and this logic in place, stress test shows that
the memory corruption issue no longer occurs.

The new eic770x_hsm device is only used for the reset-CEASE logic at
the moment, and may be extended to a fully functional HSM device in
the future.

[1] https://github.com/eswincomputing/EIC7700X-SoC-Technical-Reference-Manual

Fixes: e5797e0688c1 ("platform: generic: eswin: add EIC7700")
Signed-off-by: Bo Gan <ganboing@gmail.com>
---
 platform/generic/eswin/eic770x.c         | 105 ++++++++++++++++++++---
 platform/generic/eswin/hfp.c             |   4 +-
 platform/generic/include/eswin/eic770x.h |  20 +++--
 3 files changed, 113 insertions(+), 16 deletions(-)

diff --git a/platform/generic/eswin/eic770x.c b/platform/generic/eswin/eic770x.c
index 7330df9f..237fb06d 100644
--- a/platform/generic/eswin/eic770x.c
+++ b/platform/generic/eswin/eic770x.c
@@ -10,14 +10,96 @@
 #include <sbi/sbi_console.h>
 #include <sbi/sbi_system.h>
 #include <sbi/sbi_math.h>
+#include <sbi/sbi_hsm.h>
+#include <sbi/sbi_ipi.h>
 #include <sbi/sbi_hart_pmp.h>
 #include <sbi/sbi_hart_protection.h>
+#include <sbi_utils/hsm/fdt_hsm_sifive_inst.h>
 #include <eswin/eic770x.h>
 #include <eswin/hfp.h>
 
 static struct sbi_hart_protection eswin_eic7700_pmp_protection;
+static volatile bool eic770x_power_down = false;
 
-static int eic770x_system_reset_check(u32 type, u32 reason)
+static int eic770x_hart_start(u32 hartid, ulong saddr)
+{
+	u32 hartindex = sbi_hartid_to_hartindex(hartid);
+
+	/*
+	 * saddr is ignored intentionally.
+	 * For non-power-down scenarios, eic770x_hart_stop simply
+	 * returns, putting the hart in atomic_read(&hdata->state)
+	 * loop in sbi_hsm_hart_wait. We wake it up if it's in wfi()
+	 */
+	return sbi_ipi_raw_send(hartindex, true);
+}
+
+static int eic770x_hart_stop()
+{
+	/*
+	 * fence to enforce all previous ipi clears are done
+	 * Refer to comments below in eic770x_cease_other_harts
+	 */
+	asm volatile ("fence o, r");
+
+	if (!eic770x_power_down)
+		return SBI_ENOTSUPP;
+
+	sifive_cease();
+}
+
+void eic770x_cease_other_harts(void)
+{
+	u32 to_cease[2] = {};
+
+	eic770x_power_down = true;
+	sbi_for_each_hartindex(i) {
+		u32 hartid = sbi_hartindex_to_hartid(i);
+		u32 die    = hart_die(hartid);
+		u32 core   = hart_core(hartid);
+
+		/* Only wait for other harts */
+		if (i == current_hartindex())
+			continue;
+		/*
+		 * Bring harts out of WFI in sbi_hsm_hart_wait
+		 * Harts won't miss this IPI, because:
+		 *  1. If hart goes to wfi() in sbi_hsm_hart_wait,
+		 *     it must have not observed eic770x_power_down
+		 *  2. If it hasn't observed eic770x_power_down,
+		 *     then it must haven't observed the IPI sent,
+		 *     given the wmb() in sbi_ipi_raw_send
+		 *  3. Given the fence o, r, any previous ipi_clear
+		 *     can't fall-through the read of eic770x_power_down
+		 */
+		sbi_ipi_raw_send(i, false);
+		to_cease[die] |= EIC770X_MC_CEASE_BIT(core);
+	}
+
+	for (u32 die = 0; die < array_size(to_cease); die++) {
+		/*
+		 * MCPU status indicates the wfi/debug/halt/cease status
+		 * of each individual harts in the same die. The value
+		 * can change on the fly, but for ceased harts, the cease
+		 * bit remains high until reset
+		 */
+		u32 *status = (u32*)EIC770X_MCPU_STATUS(die);
+
+		if (!to_cease[die])
+			continue;
+
+		/* Wait for mcput_cease_from_tile_x */
+		while ((readl(status) & to_cease[die]) != to_cease[die]);
+	}
+}
+
+static const struct sbi_hsm_device eswin_eic770x_hsm = {
+	.name	      = "eic770x_hsm",
+	.hart_start   = eic770x_hart_start,
+	.hart_stop    = eic770x_hart_stop,
+};
+
+static int eic7700_system_reset_check(u32 type, u32 reason)
 {
 	switch (type) {
 	case SBI_SRST_RESET_TYPE_COLD_REBOOT:
@@ -28,23 +110,23 @@ static int eic770x_system_reset_check(u32 type, u32 reason)
 	}
 }
 
-static void eic770x_system_reset(u32 type, u32 reason)
+static void eic7700_system_reset(u32 type, u32 reason)
 {
 	switch (type) {
 	case SBI_SRST_RESET_TYPE_COLD_REBOOT:
 	case SBI_SRST_RESET_TYPE_WARM_REBOOT:
-		sbi_printf("%s: resetting...\n", __func__);
-		writel(EIC770X_SYSCRG_RST_VAL, (void *)EIC770X_SYSCRG_RST);
+		eic770x_cease_other_harts();
+		writel(EIC770X_SYSRST_VAL, (void *)EIC770X_SYSCRG_SYSRST);
 	}
 
-	sbi_hart_hang();
+	sifive_cease();
 }
 
 static struct sbi_system_reset_device *board_reset = NULL;
-static struct sbi_system_reset_device eic770x_reset = {
-	.name = "eic770x_reset",
-	.system_reset_check = eic770x_system_reset_check,
-	.system_reset = eic770x_system_reset,
+static struct sbi_system_reset_device eic7700_reset = {
+	.name = "eic7700_reset",
+	.system_reset_check = eic7700_system_reset_check,
+	.system_reset = eic7700_system_reset,
 };
 
 #define add_root_mem_chk(...) do { \
@@ -145,7 +227,7 @@ static int eswin_eic7700_early_init(bool cold_boot)
 
 	if (board_reset)
 		sbi_system_reset_add_device(board_reset);
-	sbi_system_reset_add_device(&eic770x_reset);
+	sbi_system_reset_add_device(&eic7700_reset);
 
 	/* Enable bus blocker */
 	writel(1, (void*)EIC770X_TL64D2D_OUT);
@@ -231,6 +313,9 @@ static int eswin_eic7700_final_init(bool cold_boot)
 	int rc;
 
 
+	if (cold_boot)
+		sbi_hsm_set_device(&eswin_eic770x_hsm);
+
 	/**
 	 * Do generic_final_init stuff first, because it touchs FDT.
 	 * After final_init, we'll block entire memory port with the
diff --git a/platform/generic/eswin/hfp.c b/platform/generic/eswin/hfp.c
index eabed191..a6e73e18 100644
--- a/platform/generic/eswin/hfp.c
+++ b/platform/generic/eswin/hfp.c
@@ -11,6 +11,7 @@
 #include <sbi/sbi_hart.h>
 #include <sbi/sbi_ecall_interface.h>
 #include <sbi_utils/serial/uart8250.h>
+#include <sbi_utils/hsm/fdt_hsm_sifive_inst.h>
 #include <eswin/eic770x.h>
 #include <eswin/hfp.h>
 
@@ -94,6 +95,7 @@ static int hfp_system_reset_check(u32 type, u32 reason)
 
 static void hfp_system_reset(u32 type, u32 reason)
 {
+	eic770x_cease_other_harts();
 	switch (type) {
 	case SBI_SRST_RESET_TYPE_SHUTDOWN:
 		hfp_send_bmc_msg(HFP_MSG_NOTIFY, HFP_CMD_POWER_OFF,
@@ -104,7 +106,7 @@ static void hfp_system_reset(u32 type, u32 reason)
 				NULL, 0);
 		break;
 	}
-	sbi_hart_hang();
+	sifive_cease();
 }
 
 static struct sbi_system_reset_device hfp_reset = {
diff --git a/platform/generic/include/eswin/eic770x.h b/platform/generic/include/eswin/eic770x.h
index 67764ec0..fe7c1f58 100644
--- a/platform/generic/include/eswin/eic770x.h
+++ b/platform/generic/include/eswin/eic770x.h
@@ -14,6 +14,8 @@ struct eic770x_board_override {
 	struct sbi_system_reset_device *reset_dev;
 };
 
+void eic770x_cease_other_harts(void);
+
 /* CSRs */
 #define EIC770X_CSR_BRPREDICT	0x7c0
 #define EIC770X_CSR_FEAT0	0x7c1
@@ -55,11 +57,16 @@ struct eic770x_board_override {
 #define EIC770X_UART_REG_SHIFT	2
 #define EIC770X_UART_REG_WIDTH	4
 
-#define EIC770X_SYSCRG		(EIC770X_SYSPORT_LOCAL + 0x11828000UL)
-#define EIC770X_SYSCRG_LSPCLK0	(EIC770X_SYSCRG + 0x200UL)
-#define EIC770X_SYSCRG_SYSCLK	(EIC770X_SYSCRG + 0x20cUL)
-#define EIC770X_SYSCRG_RST	(EIC770X_SYSCRG + 0x300UL)
-#define EIC770X_SYSCRG_RST_VAL	0x1AC0FFE6UL
+#define EIC770X_SYSCON(d)	(EIC770X_SYSPORT_BASE(d) + 0x11810000UL)
+#define EIC770X_MCPU_STATUS(d)	(EIC770X_SYSCON(d) + 0x608UL)
+#define EIC770X_MC_CEASE_BIT(c)	(1UL << (15 - c))
+
+#define EIC770X_SYSCRG(d)	(EIC770X_SYSPORT_BASE(d) + 0x11828000UL)
+#define EIC770X_SYSCRG_LOCAL	(EIC770X_SYSPORT_LOCAL + 0x11828000UL)
+#define EIC770X_SYSCRG_LSPCLK0	(EIC770X_SYSCRG_LOCAL + 0x200UL)
+#define EIC770X_SYSCRG_MCCLK(d) (EIC770X_SYSCRG(d) + 0x208UL)
+#define EIC770X_SYSCRG_SYSCLK	(EIC770X_SYSCRG_LOCAL + 0x20cUL)
+#define EIC770X_SYSCRG_SYSRST	(EIC770X_SYSCRG_LOCAL + 0x300UL)
 
 /* Memory Ports */
 #define EIC770X_MEMPORT_BASE	0x0080000000UL // 2G
@@ -98,4 +105,7 @@ struct eic770x_board_override {
 		divisor > 2 ? divisor : 2; 		\
 	})
 
+/* Reset definitions */
+#define EIC770X_SYSRST_VAL	0x1AC0FFE6UL
+
 #endif
-- 
2.34.1


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