clocksource/drivers/timer-sp804: Fix read_current_timer() issue when clock source...

Register a valid read_current_timer() function for the
SP804 timer on ARM32.

On ARM32 platforms, when the SP804 timer is selected as the clocksource,
the driver does not register a valid read_current_timer() function.
As a result, features that rely on this API—such as rdseed—consistently
return incorrect values.

To fix this, a delay_timer structure is registered during the SP804
driver's initialization. The read_current_timer() function is implemented
using the existing sp804_read() logic, and the timer frequency is reused
from the already-initialized clocksource.

Signed-off-by: Stephen Eta Zhou <stephen.eta.zhou@gmail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://patch.msgid.link/20250525-sp804-fix-read_current_timer-v4-1-87a9201fa4ec@gmail.com

diff --git a/drivers/clocksource/timer-sp804.c b/drivers/clocksource/timer-sp804.c
index cd1916c0532507fb3ce7a11bfab4815906e326d5..e82a95ea472478ae096b2bf7abea0d65a7bca480 100644 (file)
--- a/drivers/clocksource/timer-sp804.c
+++ b/drivers/clocksource/timer-sp804.c
@@ -21,6 +21,10 @@
 #include <linux/of_irq.h>
 #include <linux/sched_clock.h>
 
+#ifdef CONFIG_ARM
+#include <linux/delay.h>
+#endif
+
 #include "timer-sp.h"
 
 /* Hisilicon 64-bit timer(a variant of ARM SP804) */
@@ -102,6 +106,23 @@ static u64 notrace sp804_read(void)
        return ~readl_relaxed(sched_clkevt->value);
 }
 
+#ifdef CONFIG_ARM
+static struct delay_timer delay;
+static unsigned long sp804_read_delay_timer_read(void)
+{
+       return sp804_read();
+}
+
+static void sp804_register_delay_timer(int freq)
+{
+       delay.freq = freq;
+       delay.read_current_timer = sp804_read_delay_timer_read;
+       register_current_timer_delay(&delay);
+}
+#else
+static inline void sp804_register_delay_timer(int freq) {}
+#endif
+
 static int __init sp804_clocksource_and_sched_clock_init(void __iomem *base,
                                                         const char *name,
                                                         struct clk *clk,
@@ -114,6 +135,8 @@ static int __init sp804_clocksource_and_sched_clock_init(void __iomem *base,
        if (rate < 0)
                return -EINVAL;
 
+       sp804_register_delay_timer(rate);
+
        clkevt = sp804_clkevt_get(base);
 
        writel(0, clkevt->ctrl);
@@ -318,6 +341,7 @@ static int __init sp804_of_init(struct device_node *np, struct sp804_timer *time
                if (ret)
                        goto err;
        }
+
        initialized = true;
 
        return 0;