On Thu, Jul 20, 2023 at 02:29:09PM +0300, Nikita Shubin via B4 Relay wrote:
From: Nikita Shubin nikita.shubin@maquefel.me
This us a rewrite of EP93xx timer driver in arch/arm/mach-ep93xx/timer-ep93xx.c trying to do everything the device tree way:
- Make every IO-access relative to a base address and dynamic so we can do a dynamic ioremap and get going.
- Find register range and interrupt from the device tree.
...
+ bits.h
+#include <linux/clockchips.h> +#include <linux/clocksource.h> +#include <linux/init.h> +#include <linux/interrupt.h> +#include <linux/io.h> +#include <linux/io-64-nonatomic-lo-hi.h> +#include <linux/irq.h> +#include <linux/kernel.h> +#include <linux/of_address.h> +#include <linux/of_irq.h> +#include <linux/sched_clock.h>
...
+/*************************************************************************
Won't you marc it as a DOC: section?
- Timer handling for EP93xx
- The ep93xx has four internal timers. Timers 1, 2 (both 16 bit) and
- 3 (32 bit) count down at 508 kHz, are self-reloading, and can generate
- an interrupt on underflow. Timer 4 (40 bit) counts down at 983.04 kHz,
- is free-running, and can't generate interrupts.
- The 508 kHz timers are ideal for use for the timer interrupt, as the
- most common values of HZ divide 508 kHz nicely. We pick the 32 bit
- timer (timer 3) to get as long sleep intervals as possible when using
- CONFIG_NO_HZ.
- The higher clock rate of timer 4 makes it a better choice than the
- other timers for use as clock source and for sched_clock(), providing
- a stable 40 bit time base.
- */
...
+/*
- This read-only register contains the low word of the time stamp debug timer
- ( Timer4). When this register is read, the high byte of the Timer4 counter is
One too many spaces.
- saved in the Timer4ValueHigh register.
- */
...
+static irqreturn_t ep93xx_timer_interrupt(int irq, void *dev_id) +{
- struct ep93xx_tcu *tcu = ep93xx_tcu;
- struct clock_event_device *evt = dev_id;
- /* Writing any value clears the timer interrupt */
- writel(1, tcu->base + EP93XX_TIMER3_CLEAR);
Would 0 suffice?
- evt->event_handler(evt);
- return IRQ_HANDLED;
+}
...
+static int __init ep93xx_timer_of_init(struct device_node *np) +{
- int irq;
- unsigned long flags = IRQF_TIMER | IRQF_IRQPOLL;
- struct ep93xx_tcu *tcu;
- int ret;
- tcu = kzalloc(sizeof(*tcu), GFP_KERNEL);
- if (!tcu)
return -ENOMEM;- tcu->base = of_iomap(np, 0);
fwnode_iomap()? See below why it might make sense.
- if (!tcu->base) {
pr_err("Can't remap registers\n");
First of all, you may utilize pr_fmt(). Second, you may add %pOF for better user experience.
ret = -ENXIO;goto out_free;- }
- irq = irq_of_parse_and_map(np, 0);
fwnode_irq_get() which is better in terms of error handling.
- if (irq == 0)
irq = -EINVAL;- if (irq < 0) {
pr_err("EP93XX Timer Can't parse IRQ %d", irq);
As per above.
goto out_free;- }
...
+}