Merge tag 'printk-for-6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

Pull printk updates from Petr Mladek:

 - Allow creaing nbcon console drivers with an unsafe write_atomic()
   callback that can only be called by the final nbcon_atomic_flush_unsafe().
   Otherwise, the driver would rely on the kthread.

   It is going to be used as the-best-effort approach for an
   experimental nbcon netconsole driver, see

     https://lore.kernel.org/r/[email protected]

   Note that a safe .write_atomic() callback is supposed to work in NMI
   context. But some networking drivers are not safe even in IRQ
   context:

     https://lore.kernel.org/r/oc46gdpmmlly5o44obvmoatfqo5bhpgv7pabpvb6sjuqioymcg@gjsma3ghoz35

   In an ideal world, all networking drivers would be fixed first and
   the atomic flush would be blocked only in NMI context. But it brings
   the question how reliable networking drivers are when the system is
   in a bad state. They might block flushing more reliable serial
   consoles which are more suitable for serious debugging anyway.

 - Allow to use the last 4 bytes of the printk ring buffer.

 - Prevent queuing IRQ work and block printk kthreads when consoles are
   suspended. Otherwise, they create non-necessary churn or even block
   the suspend.

 - Release console_lock() between each record in the kthread used for
   legacy consoles on RT. It might significantly speed up the boot.

 - Release nbcon context between each record in the atomic flush. It
   prevents stalls of the related printk kthread after it has lost the
   ownership in the middle of a record

 - Add support for NBCON consoles into KDB

 - Add %ptsP modifier for printing struct timespec64 and use it where
   possible

 - Misc code clean up

* tag 'printk-for-6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux: (48 commits)
  printk: Use console_is_usable on console_unblank
  arch: um: kmsg_dump: Use console_is_usable
  drivers: serial: kgdboc: Drop checks for CON_ENABLED and CON_BOOT
  lib/vsprintf: Unify FORMAT_STATE_NUM handlers
  printk: Avoid irq_work for printk_deferred() on suspend
  printk: Avoid scheduling irq_work on suspend
  printk: Allow printk_trigger_flush() to flush all types
  tracing: Switch to use %ptSp
  scsi: snic: Switch to use %ptSp
  scsi: fnic: Switch to use %ptSp
  s390/dasd: Switch to use %ptSp
  ptp: ocp: Switch to use %ptSp
  pps: Switch to use %ptSp
  PCI: epf-test: Switch to use %ptSp
  net: dsa: sja1105: Switch to use %ptSp
  mmc: mmc_test: Switch to use %ptSp
  media: av7110: Switch to use %ptSp
  ipmi: Switch to use %ptSp
  igb: Switch to use %ptSp
  e1000e: Switch to use %ptSp
  ...

Author: torvalds

Documentation/core-api/printk-formats.rst

@@ -547,11 +547,13 @@ Time and date
 	%pt[RT]s		YYYY-mm-dd HH:MM:SS
 	%pt[RT]d		YYYY-mm-dd
 	%pt[RT]t		HH:MM:SS
-	%pt[RT][dt][r][s]
+	%ptSp			<seconds>.<nanoseconds>
+	%pt[RST][dt][r][s]
 
 For printing date and time as represented by::
 
-	R  struct rtc_time structure
+	R  content of struct rtc_time
+	S  content of struct timespec64
 	T  time64_t type
 
 in human readable format.
@@ -563,6 +565,11 @@ The %pt[RT]s (space) will override ISO 8601 separator by using ' ' (space)
 instead of 'T' (Capital T) between date and time. It won't have any effect
 when date or time is omitted.
 
+The %ptSp is equivalent to %lld.%09ld for the content of the struct timespec64.
+When the other specifiers are given, it becomes the respective equivalent of
+%ptT[dt][r][s].%09ld. In other words, the seconds are being printed in
+the human readable format followed by a dot and nanoseconds.
+
 Passed by reference.
 
 struct clk

MAINTAINERS

@@ -20608,6 +20608,7 @@ R:	John Ogness <[email protected]>
 R:	Sergey Senozhatsky <[email protected]>
 S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux.git
+F:	Documentation/core-api/printk-basics.rst
 F:	include/linux/printk.h
 F:	kernel/printk/
 

arch/um/kernel/kmsg_dump.c

@@ -31,7 +31,7 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,
 		 * expected to output the crash information.
 		 */
 		if (strcmp(con->name, "ttynull") != 0 &&
-		    (console_srcu_read_flags(con) & CON_ENABLED)) {
+		    console_is_usable(con, console_srcu_read_flags(con), true)) {
 			break;
 		}
 	}

drivers/char/ipmi/ipmi_si_intf.c

@@ -275,8 +275,7 @@ void debug_timestamp(struct smi_info *smi_info, char *msg)
 	struct timespec64 t;
 
 	ktime_get_ts64(&t);
-	dev_dbg(smi_info->io.dev, "**%s: %lld.%9.9ld\n",
-		msg, t.tv_sec, t.tv_nsec);
+	dev_dbg(smi_info->io.dev, "**%s: %ptSp\n", msg, &t);
 }
 #else
 #define debug_timestamp(smi_info, x)

drivers/char/ipmi/ipmi_ssif.c

@@ -1083,10 +1083,8 @@ static int sender(void *send_info, struct ipmi_smi_msg *msg)
 		struct timespec64 t;
 
 		ktime_get_real_ts64(&t);
-		dev_dbg(&ssif_info->client->dev,
-			"**Enqueue %02x %02x: %lld.%6.6ld\n",
-			msg->data[0], msg->data[1],
-			(long long)t.tv_sec, (long)t.tv_nsec / NSEC_PER_USEC);
+		dev_dbg(&ssif_info->client->dev, "**Enqueue %02x %02x: %ptSp\n",
+			msg->data[0], msg->data[1], &t);
 	}
 	return IPMI_CC_NO_ERROR;
 }

drivers/dma-buf/sync_debug.c

@@ -59,7 +59,7 @@ static void sync_print_fence(struct seq_file *s,
 		struct timespec64 ts64 =
 			ktime_to_timespec64(fence->timestamp);
 
-		seq_printf(s, "@%lld.%09ld", (s64)ts64.tv_sec, ts64.tv_nsec);
+		seq_printf(s, "@%ptSp", &ts64);
 	}
 
 	seq_printf(s, ": %lld", fence->seqno);

drivers/gpu/drm/amd/amdgpu/amdgpu_dev_coredump.c

@@ -217,8 +217,7 @@ amdgpu_devcoredump_read(char *buffer, loff_t offset, size_t count,
 	drm_printf(&p, "version: " AMDGPU_COREDUMP_VERSION "\n");
 	drm_printf(&p, "kernel: " UTS_RELEASE "\n");
 	drm_printf(&p, "module: " KBUILD_MODNAME "\n");
-	drm_printf(&p, "time: %lld.%09ld\n", coredump->reset_time.tv_sec,
-		   coredump->reset_time.tv_nsec);
+	drm_printf(&p, "time: %ptSp\n", &coredump->reset_time);
 
 	if (coredump->reset_task_info.task.pid)
 		drm_printf(&p, "process_name: %s PID: %d\n",

drivers/gpu/drm/drm_vblank.c

@@ -794,10 +794,8 @@ drm_crtc_vblank_helper_get_vblank_timestamp_internal(
 	ts_vblank_time = ktime_to_timespec64(*vblank_time);
 
 	drm_dbg_vbl(dev,
-		    "crtc %u : v p(%d,%d)@ %lld.%06ld -> %lld.%06ld [e %d us, %d rep]\n",
-		    pipe, hpos, vpos,
-		    (u64)ts_etime.tv_sec, ts_etime.tv_nsec / 1000,
-		    (u64)ts_vblank_time.tv_sec, ts_vblank_time.tv_nsec / 1000,
+		    "crtc %u : v p(%d,%d)@ %ptSp -> %ptSp [e %d us, %d rep]\n",
+		    pipe, hpos, vpos, &ts_etime, &ts_vblank_time,
 		    duration_ns / 1000, i);
 
 	return true;

drivers/gpu/drm/msm/disp/msm_disp_snapshot_util.c

@@ -82,8 +82,7 @@ void msm_disp_state_print(struct msm_disp_state *state, struct drm_printer *p)
 	drm_printf(p, "kernel: " UTS_RELEASE "\n");
 	drm_printf(p, "module: " KBUILD_MODNAME "\n");
 	drm_printf(p, "dpu devcoredump\n");
-	drm_printf(p, "time: %lld.%09ld\n",
-		state->time.tv_sec, state->time.tv_nsec);
+	drm_printf(p, "time: %ptSp\n", &state->time);
 
 	list_for_each_entry_safe(block, tmp, &state->blocks, node) {
 		drm_printf(p, "====================%s================\n", block->name);

drivers/gpu/drm/msm/msm_gpu.c

@@ -197,8 +197,7 @@ static ssize_t msm_gpu_devcoredump_read(char *buffer, loff_t offset,
 	drm_printf(&p, "---\n");
 	drm_printf(&p, "kernel: " UTS_RELEASE "\n");
 	drm_printf(&p, "module: " KBUILD_MODNAME "\n");
-	drm_printf(&p, "time: %lld.%09ld\n",
-		state->time.tv_sec, state->time.tv_nsec);
+	drm_printf(&p, "time: %ptSp\n", &state->time);
 	if (state->comm)
 		drm_printf(&p, "comm: %s\n", state->comm);
 	if (state->cmd)