[RFC PATCH v1 07/10] clocksource: clint: Add support for ACLINT MTIMER device

[Anup Patel]

The RISC-V ACLINT specification is a modular specification and the
ACLINT MTIMER device is compatible with the M-mode timer functionality
of the CLINT device. This patch extends the CLINT driver to support
both CLINT device and ACLINT MTIMER device.

Signed-off-by: Anup Patel <anup.patel at wdc.com>
---
 drivers/clocksource/timer-clint.c | 43 +++++++++++++++++++++----------
 1 file changed, 30 insertions(+), 13 deletions(-)

diff --git a/drivers/clocksource/timer-clint.c b/drivers/clocksource/timer-clint.c
index dfdcd94c1fd5..ca329c450810 100644
--- a/drivers/clocksource/timer-clint.c
+++ b/drivers/clocksource/timer-clint.c
@@ -2,8 +2,15 @@
 /*
  * Copyright (C) 2020 Western Digital Corporation or its affiliates.
  *
- * Most of the M-mode (i.e. NoMMU) RISC-V systems usually have a
- * CLINT MMIO timer device.
+ * Most of the M-mode (i.e. NoMMU) RISC-V systems usually have a CLINT
+ * MMIO device which is a composite device capable of injecting M-mode
+ * software interrupts and M-mode timer interrupts.
+ *
+ * The RISC-V ACLINT specification is modular in nature and defines
+ * separate devices for M-mode software interrupt (MSWI), M-mode timer
+ * (MTIMER) and S-mode software interrupt (SSWI).
+ *
+ * This is a common driver for CLINT device and ACLINT MTIMER device.
  */
 
 #define pr_fmt(fmt) "clint: " fmt
@@ -21,14 +28,20 @@
 #include <linux/smp.h>
 #include <linux/timex.h>
 
-#ifndef CONFIG_RISCV_M_MODE
+#ifdef CONFIG_RISCV_M_MODE
 #include <asm/clint.h>
+
+u64 __iomem *clint_time_val;
+EXPORT_SYMBOL(clint_time_val);
 #endif
 
 #define CLINT_IPI_OFF		0
 #define CLINT_TIMER_CMP_OFF	0x4000
 #define CLINT_TIMER_VAL_OFF	0xbff8
 
+#define ACLINT_MTIMER_CMP_OFF	0x0000
+#define ACLINT_MTIMER_VAL_OFF	0x7ff8
+
 /* CLINT manages IPI and Timer for RISC-V M-mode  */
 static u32 __iomem *clint_ipi_base;
 static u64 __iomem *clint_timer_cmp;
@@ -36,11 +49,6 @@ static u64 __iomem *clint_timer_val;
 static unsigned long clint_timer_freq;
 static unsigned int clint_timer_irq;
 
-#ifdef CONFIG_RISCV_M_MODE
-u64 __iomem *clint_time_val;
-EXPORT_SYMBOL(clint_time_val);
-#endif
-
 static void clint_send_ipi(const struct cpumask *target)
 {
 	unsigned int cpu;
@@ -191,9 +199,15 @@ static int __init clint_timer_init_dt(struct device_node *np)
 		return -ENODEV;
 	}
 
-	clint_ipi_base = base + CLINT_IPI_OFF;
-	clint_timer_cmp = base + CLINT_TIMER_CMP_OFF;
-	clint_timer_val = base + CLINT_TIMER_VAL_OFF;
+	if (of_device_is_compatible(np, "riscv,aclint-mtimer")) {
+		clint_ipi_base = NULL;
+		clint_timer_cmp = base + ACLINT_MTIMER_CMP_OFF;
+		clint_timer_val = base + ACLINT_MTIMER_VAL_OFF;
+	} else {
+		clint_ipi_base = base + CLINT_IPI_OFF;
+		clint_timer_cmp = base + CLINT_TIMER_CMP_OFF;
+		clint_timer_val = base + CLINT_TIMER_VAL_OFF;
+	}
 	clint_timer_freq = riscv_timebase;
 
 #ifdef CONFIG_RISCV_M_MODE
@@ -230,8 +244,10 @@ static int __init clint_timer_init_dt(struct device_node *np)
 		goto fail_free_irq;
 	}
 
-	riscv_set_ipi_ops(&clint_ipi_ops);
-	clint_clear_ipi();
+	if (clint_ipi_base) {
+		riscv_set_ipi_ops(&clint_ipi_ops);
+		clint_clear_ipi();
+	}
 
 	return 0;
 
@@ -244,3 +260,4 @@ static int __init clint_timer_init_dt(struct device_node *np)
 
 TIMER_OF_DECLARE(clint_timer, "riscv,clint0", clint_timer_init_dt);
 TIMER_OF_DECLARE(clint_timer1, "sifive,clint0", clint_timer_init_dt);
+TIMER_OF_DECLARE(clint_timer2, "riscv,aclint-mtimer", clint_timer_init_dt);
-- 
2.25.1