Merge patch series "Uthreads"

Jerome Forissier <jerome.forissier@linaro.org> says:

This series introduces threads and uses them to improve the performance
of the USB bus scanning code and to implement background jobs in the
shell via two new commands: 'spawn' and 'wait'.

The threading framework is called 'uthread' and is inspired from the
barebox threads [2]. setjmp() and longjmp() are used to save and
restore contexts, as well as a non-standard extension called initjmp().
This new function is added in several patches, one for each
architecture that supports HAVE_SETJMP. A new symbol is defined:
HAVE_INITJMP. Two tests, one for initjmp() and one for the uthread
scheduling, are added to the lib suite.

After introducing threads and making schedule() and udelay() a thread
re-scheduling point, the USB stack initialization is modified to benefit
from concurrency when UTHREAD is enabled, where uthreads are used in
usb_init() to initialize and scan multiple busses at the same time.
The code was tested on arm64 and arm QEMU with 4 simulated XHCI buses
and some devices. On this platform the USB scan takes 2.2 s instead of
5.6 s. Tested on i.MX93 EVK with two USB hubs, one ethernet adapter and
one webcam on each, "usb start" takes 2.4 s instead of 4.6 s.

Finally, the spawn and wait commands are introduced, allowing the use of
threads from the shell. Tested on the i.MX93 EVK with a spinning HDD
connected to USB1 and the network connected to ENET1. The USB plus DHCP
init sequence "spawn usb start; spawn dhcp; wait" takes 4.5 seconds
instead of 8 seconds for "usb start; dhcp".

[1] https://patchwork.ozlabs.org/project/uboot/list/?series=446674
[2] https://github.com/barebox/barebox/blob/master/common/bthread.c

Link: https://lore.kernel.org/r/20250418141114.2056981-1-jerome.forissier@linaro.org

1 files changed, 8 insertions, 1 deletions

diff --git a/lib/time.c b/lib/time.c
index d88edafb196..0e9b079f9cf 100644
--- a/lib/time.c
+++ b/lib/time.c
@@ -17,6 +17,7 @@
 #include <asm/global_data.h>
 #include <asm/io.h>
 #include <linux/delay.h>
+#include <uthread.h>
 
 #ifndef CFG_WD_PERIOD
 # define CFG_WD_PERIOD	(10 * 1000 * 1000)	/* 10 seconds default */
@@ -197,7 +198,13 @@ void udelay(unsigned long usec)
 	do {
 		schedule();
 		kv = usec > CFG_WD_PERIOD ? CFG_WD_PERIOD : usec;
-		__udelay(kv);
+		if (CONFIG_IS_ENABLED(UTHREAD)) {
+			ulong t0 = timer_get_us();
+			while (timer_get_us() - t0 < kv)
+				uthread_schedule();
+		} else {
+			__udelay(kv);
+		}
 		usec -= kv;
 	} while(usec);
 }