misc: ioc4: simplify wave period measurement in clock_calibrate (769105aa) · Commits · 戴 / test

The loop for measuring the square wave periods over some cycles is refactored to be more easily readable. This includes avoiding a "by-hand-implemented" for loop with a "real" one and adding some comments. Furthermore the following compiler warning is avoided by this patch: drivers/misc/ioc4.c: In function ‘ioc4_probe’: drivers/misc/ioc4.c:194:16: warning: ‘start’ may be used uninitialized in this function [-Wmaybe-uninitialized] period = (end - start) / ^ drivers/misc/ioc4.c:148:11: note: ‘start’ was declared here uint64_t start, end, period; ^ Signed-off-by:

Richard Leitner <dev@g0hl1n.net> Acked-by:

Arnd Bergmann <arnd@arndb.de> Signed-off-by:

Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/ioc4.c

+16 −15

Original line number	Diff line number	Diff line
		@@ -144,9 +144,9 @@ ioc4_clock_calibrate(struct ioc4_driver_data *idd)
		{
		union ioc4_int_out int_out;
		union ioc4_gpcr gpcr;
		unsigned int state, last_state = 1;
		unsigned int state, last_state;
		uint64_t start, end, period;
		unsigned int count = 0;
		unsigned int count;

		/* Enable output */
		gpcr.raw = 0;
		@@ -167,19 +167,20 @@ ioc4_clock_calibrate(struct ioc4_driver_data *idd)
		mmiowb();

		/* Check square wave period averaged over some number of cycles */
		do {
		start = ktime_get_ns();
		state = 1; /* make sure the first read isn't a rising edge */
		for (count = 0; count <= IOC4_CALIBRATE_END; count++) {
		do { /* wait for a rising edge */
		last_state = state;
		int_out.raw = readl(&idd->idd_misc_regs->int_out.raw);
		state = int_out.fields.int_out;
		if (!last_state && state) {
		count++;
		if (count == IOC4_CALIBRATE_END) {
		end = ktime_get_ns();
		break;
		} else if (count == IOC4_CALIBRATE_DISCARD)
		} while (last_state \|\| !state);

		/* discard the first few cycles */
		if (count == IOC4_CALIBRATE_DISCARD)
		start = ktime_get_ns();
		}
		last_state = state;
		} while (1);
		end = ktime_get_ns();

		/* Calculation rearranged to preserve intermediate precision.
		* Logically:

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