Add claim support in plictool

JOURNAL.md

@@ -4311,3 +4311,34 @@ helpful.
 For that I need to first switch to the 8250/16550 driver. Let's try switch to
 the ttyS0 without enabling flow control yet. We probably need to change the
 stage1 and stage2 scripts to follow the proper console device.
+
+It works, but very slowly:
+
+    [    0.000000] Kernel command line: root=/dev/ram0 loglevel=7 rw earlycon=sbi console=ttyS0,115200n8 debug2 ...
+    ...
+    [   42.069358] Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled
+    [   42.473860] of_serial 40001000.serial: error -ENXIO: IRQ index 0 not found
+    [   42.559263] printk: legacy console [ttyS0] disabled
+    [   42.614225] 40001000.serial: ttyS0 at MMIO 0x40001000 (irq = 0, base_baud = 3125000) is a 16550
+    [   42.645519] printk: legacy console [ttyS0] enabled
+    [   42.645519] printk: legacy console [ttyS0] enabled
+    [   42.656865] printk: legacy bootconsole [sbi0] disabled
+    [   42.656865] printk: legacy bootconsole [sbi0] disabled
+    [   42.896358] 40003000.serial: ttyS1 at MMIO 0x40003000 (irq = 1, base_baud = 3125000) is a 16550
+    [   42.999450] SuperH (H)SCI(F) driver initialized
+    ...
+    ~ # stty -a
+    speed 115200 baud;stty: standard input
+     line = 0;
+    intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>;
+    eol2 = <undef>; swtch = <undef>; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R;
+    werase = ^W; lnext = ^V; flush = ^O; min = 1; time = 0;
+    -parenb -parodd -cmspar cs8 hupcl -cstopb cread clocal -crtscts
+    -ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon -ixoff
+    -iuclc -ixany -imaxbel -iutf8
+    opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
+    isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt
+    echoctl echoke -flusho -extproc
+
+Let's add the ability to claim a context in the plictool, as I suspect the claim
+may be broken.

tools/plictool.c

@@ -8,9 +8,10 @@
  *   v0.0.1 (2024-09-03): Initial version.
  *   v0.0.2 (2024-09-04): Print contexts in another line and masked information.
  *   v0.0.3 (2024-09-04): Make output format more clear and add manual.
+ *   v0.0.4 (2024-09-30): Implement support for claiming an interrupt.
  */
 
-#define VERSION "v0.0.3"
+#define VERSION "v0.0.4"
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -21,10 +22,12 @@
 #include <sys/mman.h>
 #include <errno.h>
 
+enum op { DUMP, CLAIM } operation = DUMP;
 const char *plic_address_str = "0x40800000";
 long ncontexts = 15872L;
 long maxsources = 1024L;
 long nsources = 1024L;
+long claim_ctx = 0;
 
 static void
 usage(void)
@@ -34,7 +37,7 @@ usage(void)
 "    plictool - dump PLIC information\n"
 "\n"
 "SYNOPSIS\n"
-"    plictool [-a addr] [-s nsources] [-c ncontexts]\n"
+"    plictool [-a addr] [-s nsources] [-c ncontexts] [-C ctx]\n"
 "\n"
 "DESCRIPTION\n"
 "    Dumps information about the RISC-V PLIC interrupt controller.\n"
@@ -49,6 +52,8 @@ usage(void)
 "      -c ncontexts   Limit the number of contexts to print.\n"
 "                     The default is 15872.\n"
 "\n"
+"      -C ctx         Claim the interrupt on the given context.\n"
+"\n"
 "OUTPUT FORMAT\n"
 "    Information is printed for each source that has some bit set\n"
 "    in the pending or priority registers, or it has some context\n"
@@ -75,7 +80,31 @@ usage(void)
 	exit(1);
 }
 
-void dump_sources(void *base)
+static uint32_t
+read_reg(void *base, size_t offset)
+{
+	volatile uint32_t *p = base + offset;
+	return *p;
+}
+
+static void
+write_reg(void *base, size_t offset, uint32_t value)
+{
+	volatile uint32_t *p = base + offset;
+	*p = value;
+}
+
+static void
+claim_interrupt(void *base, long ctx)
+{
+	size_t offset = 0x200004L + ctx * 0x1000;
+	uint32_t value = read_reg(base, offset);
+	printf("ctx=%ld claim=%u\n", ctx, value);
+	write_reg(base, offset, value);
+}
+
+static void
+dump_sources(void *base)
 {
 	for (long s = 0; s < nsources; s++) {
 		int printed_source = 0;
@@ -133,7 +162,7 @@ int main(int argc, char *argv[])
 {
 	int opt;
 
-	while ((opt = getopt(argc, argv, "a:hs:c:")) != -1) {
+	while ((opt = getopt(argc, argv, "a:hs:c:C:")) != -1) {
 		switch (opt) {
 			case 'a':
 				plic_address_str = optarg;
@@ -144,6 +173,10 @@ int main(int argc, char *argv[])
 			case 'c':
 				ncontexts = atol(optarg);
 				break;
+			case 'C':
+				operation = CLAIM;
+				claim_ctx = atol(optarg);
+				break;
 			case 'h':
 			default: /* '?' */
 				usage();
@@ -177,7 +210,10 @@ int main(int argc, char *argv[])
 		exit(1);
 	}
 
-	dump_sources(map_base);
+	if (operation == CLAIM)
+		claim_interrupt(map_base, claim_ctx);
+	else if (operation == DUMP)
+		dump_sources(map_base);
 
 	munmap(map_base, map_size);