[RFC PATCH v2 10/11] 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 backward compatible with the M-mode timer
functionality of the CLINT device. This patch extends the CLINT
timer driver to support both CLINT device and ACLINT MTIMER device.

Signed-off-by: Anup Patel <anup.patel at wdc.com>
Reviewed-by: Bin Meng <bmeng.cn at gmail.com>
---
 drivers/clocksource/timer-clint.c | 35 ++++++++++++++++++++++---------
 1 file changed, 25 insertions(+), 10 deletions(-)

diff --git a/drivers/clocksource/timer-clint.c b/drivers/clocksource/timer-clint.c
index 3b68ed53fe4a..bf89744cd12a 100644
--- a/drivers/clocksource/timer-clint.c
+++ b/drivers/clocksource/timer-clint.c
@@ -2,8 +2,16 @@
 /*
  * 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 timer driver for the CLINT device and the ACLINT
+ * MTIMER device.
  */
 
 #define pr_fmt(fmt) "clint: " fmt
@@ -21,25 +29,26 @@
 #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 u64 __iomem *clint_timer_cmp;
 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
-
 #ifdef CONFIG_64BIT
 #define clint_get_cycles()	readq_relaxed(clint_timer_val)
 #else
@@ -170,8 +179,13 @@ static int __init clint_timer_init_dt(struct device_node *np)
 		return -ENODEV;
 	}
 
-	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_timer_cmp = base + ACLINT_MTIMER_CMP_OFF;
+		clint_timer_val = base + ACLINT_MTIMER_VAL_OFF;
+	} else {
+		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
@@ -219,3 +233,4 @@ 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