When trying to use CMT for clockevents on R-Car gen3 SoCs, I noticed
that 'max_delta_ns' for the broadcast timer (CMT) was shown as 1000 in
/proc/timer_list. It turned out that when calculating it, the driver did
1 << 32 (causing what I think was undefined behavior) resulting in a zero
delta, later clamped to 1000 by cev_delta2ns(). The root cause turned out
to be that the driver abused *unsigned long* for the CMT register values
(which are 16/32-bit), so that the calculation of 'ch->max_match_value'
in sh_cmt_setup_channel() used the wrong branch. Using more proper 'u32'
instead fixed 'max_delta_ns' and even fixed the switching an active
clocksource to CMT (which caused the system to turn non-interactive
before).
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@xxxxxxxxxxxxxxxxxx>
---
This patch is against the 'tip.git' repo's 'timers/core' branch.
The CMT driver wasn't ever used on SH64; on R-Car gen3 (ARM64) I'm only
enabling building of this driver now, so not sure how urgent is this...
Changes in version 3:
- made the 'overflow_bit' and 'clear_bits' members of 'struct sh_cmt_info'
'u32';
- made the 2nd parameter of sh_cmt_write_cmstr() 'u32';
- made the result, the 2nd parameter, and 'o{1|2}' local variables of
sh_cmt_get_counter() 'u32';
- made the 'has_wrapped' local variables 'u32' in sh_cmt_clocksource_read()
and sh_cmt_clock_event_program_verify();
- fixed a typo in the patch description.
Changes in version 2:
- completely redid the patch, fixing abuse of *unsigned long* for the CMT
register values.
drivers/clocksource/sh_cmt.c | 72 +++++++++++++++++++------------------------
1 file changed, 33 insertions(+), 39 deletions(-)
Index: tip/drivers/clocksource/sh_cmt.c
===================================================================
--- tip.orig/drivers/clocksource/sh_cmt.c
+++ tip/drivers/clocksource/sh_cmt.c
@@ -78,18 +78,17 @@ struct sh_cmt_info {
unsigned int channels_mask;
unsigned long width; /* 16 or 32 bit version of hardware block */
- unsigned long overflow_bit;
- unsigned long clear_bits;
+ u32 overflow_bit;
+ u32 clear_bits;
/* callbacks for CMSTR and CMCSR access */
- unsigned long (*read_control)(void __iomem *base, unsigned long offs);
+ u32 (*read_control)(void __iomem *base, unsigned long offs);
void (*write_control)(void __iomem *base, unsigned long offs,
- unsigned long value);
+ u32 value);
/* callbacks for CMCNT and CMCOR access */
- unsigned long (*read_count)(void __iomem *base, unsigned long offs);
- void (*write_count)(void __iomem *base, unsigned long offs,
- unsigned long value);
+ u32 (*read_count)(void __iomem *base, unsigned long offs);
+ void (*write_count)(void __iomem *base, unsigned long offs, u32 value);
};
struct sh_cmt_channel {
@@ -103,9 +102,9 @@ struct sh_cmt_channel {
unsigned int timer_bit;
unsigned long flags;
- unsigned long match_value;
- unsigned long next_match_value;
- unsigned long max_match_value;
+ u32 match_value;
+ u32 next_match_value;
+ u32 max_match_value;
raw_spinlock_t lock;
struct clock_event_device ced;
struct clocksource cs;
@@ -160,24 +159,22 @@ struct sh_cmt_device {
#define SH_CMT32_CMCSR_CKS_RCLK1 (7 << 0)
#define SH_CMT32_CMCSR_CKS_MASK (7 << 0)
-static unsigned long sh_cmt_read16(void __iomem *base, unsigned long offs)
+static u32 sh_cmt_read16(void __iomem *base, unsigned long offs)
{
return ioread16(base + (offs << 1));
}
-static unsigned long sh_cmt_read32(void __iomem *base, unsigned long offs)
+static u32 sh_cmt_read32(void __iomem *base, unsigned long offs)
{
return ioread32(base + (offs << 2));
}
-static void sh_cmt_write16(void __iomem *base, unsigned long offs,
- unsigned long value)
+static void sh_cmt_write16(void __iomem *base, unsigned long offs, u32 value)
{
iowrite16(value, base + (offs << 1));
}
-static void sh_cmt_write32(void __iomem *base, unsigned long offs,
- unsigned long value)
+static void sh_cmt_write32(void __iomem *base, unsigned long offs, u32 value)
{
iowrite32(value, base + (offs << 2));
}
@@ -242,7 +239,7 @@ static const struct sh_cmt_info sh_cmt_i
#define CMCNT 1 /* channel register */
#define CMCOR 2 /* channel register */
-static inline unsigned long sh_cmt_read_cmstr(struct sh_cmt_channel *ch)
+static inline u32 sh_cmt_read_cmstr(struct sh_cmt_channel *ch)
{
if (ch->iostart)
return ch->cmt->info->read_control(ch->iostart, 0);
@@ -250,8 +247,7 @@ static inline unsigned long sh_cmt_read_
return ch->cmt->info->read_control(ch->cmt->mapbase, 0);
}
-static inline void sh_cmt_write_cmstr(struct sh_cmt_channel *ch,
- unsigned long value)
+static inline void sh_cmt_write_cmstr(struct sh_cmt_channel *ch, u32 value)
{
if (ch->iostart)
ch->cmt->info->write_control(ch->iostart, 0, value);
@@ -259,39 +255,35 @@ static inline void sh_cmt_write_cmstr(st
ch->cmt->info->write_control(ch->cmt->mapbase, 0, value);
}
-static inline unsigned long sh_cmt_read_cmcsr(struct sh_cmt_channel *ch)
+static inline u32 sh_cmt_read_cmcsr(struct sh_cmt_channel *ch)
{
return ch->cmt->info->read_control(ch->ioctrl, CMCSR);
}
-static inline void sh_cmt_write_cmcsr(struct sh_cmt_channel *ch,
- unsigned long value)
+static inline void sh_cmt_write_cmcsr(struct sh_cmt_channel *ch, u32 value)
{
ch->cmt->info->write_control(ch->ioctrl, CMCSR, value);
}
-static inline unsigned long sh_cmt_read_cmcnt(struct sh_cmt_channel *ch)
+static inline u32 sh_cmt_read_cmcnt(struct sh_cmt_channel *ch)
{
return ch->cmt->info->read_count(ch->ioctrl, CMCNT);
}
-static inline void sh_cmt_write_cmcnt(struct sh_cmt_channel *ch,
- unsigned long value)
+static inline void sh_cmt_write_cmcnt(struct sh_cmt_channel *ch, u32 value)
{
ch->cmt->info->write_count(ch->ioctrl, CMCNT, value);
}
-static inline void sh_cmt_write_cmcor(struct sh_cmt_channel *ch,
- unsigned long value)
+static inline void sh_cmt_write_cmcor(struct sh_cmt_channel *ch, u32 value)
{
ch->cmt->info->write_count(ch->ioctrl, CMCOR, value);
}
-static unsigned long sh_cmt_get_counter(struct sh_cmt_channel *ch,
- int *has_wrapped)
+static u32 sh_cmt_get_counter(struct sh_cmt_channel *ch, u32 *has_wrapped)
{
- unsigned long v1, v2, v3;
- int o1, o2;
+ u32 v1, v2, v3;
+ u32 o1, o2;
o1 = sh_cmt_read_cmcsr(ch) & ch->cmt->info->overflow_bit;
@@ -311,7 +303,8 @@ static unsigned long sh_cmt_get_counter(
static void sh_cmt_start_stop_ch(struct sh_cmt_channel *ch, int start)
{
- unsigned long flags, value;
+ unsigned long flags;
+ u32 value;
/* start stop register shared by multiple timer channels */
raw_spin_lock_irqsave(&ch->cmt->lock, flags);
@@ -418,11 +411,11 @@ static void sh_cmt_disable(struct sh_cmt
static void sh_cmt_clock_event_program_verify(struct sh_cmt_channel *ch,
int absolute)
{
- unsigned long new_match;
- unsigned long value = ch->next_match_value;
- unsigned long delay = 0;
- unsigned long now = 0;
- int has_wrapped;
+ u32 value = ch->next_match_value;
+ u32 new_match;
+ u32 delay = 0;
+ u32 now = 0;
+ u32 has_wrapped;
now = sh_cmt_get_counter(ch, &has_wrapped);
ch->flags |= FLAG_REPROGRAM; /* force reprogram */
@@ -619,9 +612,10 @@ static struct sh_cmt_channel *cs_to_sh_c
static u64 sh_cmt_clocksource_read(struct clocksource *cs)
{
struct sh_cmt_channel *ch = cs_to_sh_cmt(cs);
- unsigned long flags, raw;
+ unsigned long flags;
unsigned long value;
- int has_wrapped;
+ u32 has_wrapped;
+ u32 raw;
raw_spin_lock_irqsave(&ch->lock, flags);
value = ch->total_cycles;
