[PATCH 3/7] alpha: marvel: refresh environmental readings through the console

[Matt Turner <mattst88@gmail.com>]

The SRM console keeps the readings of the temperature, fan, voltage and
power supply sensors in the power and environment (P&E) nodes of the
config tree (GCT), and refreshes those of one node when asked through
config tree callback 0x28, function 0x1f. Add the callback and
marvel_cfgtree_partial_update() for a sensor driver to use, retrying,
as Tru64 UNIX does, while the console reports busy.

On an ES47 the callback takes 13 to 300 ms per node with interrupts
disabled. The console callbacks are not reentrant: a refresh on one CPU
while another printed to the SRM console killed the second CPU, and the
service processor reset the partition. So export the srmcons callback
lock and hold it around the call.

Tru64 UNIX makes this and its other runtime config tree callbacks only on
the master CPU, and the Marvel PAL TOY calls are already known to work
only on the boot CPU, so make the call there as well.

Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/include/asm/console.h      |  2 ++
 arch/alpha/include/asm/marvel_env.h   | 12 +++++++++
 arch/alpha/include/uapi/asm/console.h |  2 ++
 arch/alpha/kernel/core_marvel.c       | 48 +++++++++++++++++++++++++++++++++++
 arch/alpha/kernel/proto.h             |  1 +
 arch/alpha/kernel/srmcons.c           |  3 ++-
 arch/alpha/lib/callback_srm.S         |  1 +
 7 files changed, 68 insertions(+), 1 deletion(-)

diff --git a/arch/alpha/include/asm/console.h b/arch/alpha/include/asm/console.h
index 1cabdb6064bb..9b4a0f73c125 100644
--- a/arch/alpha/include/asm/console.h
+++ b/arch/alpha/include/asm/console.h
@@ -15,6 +15,8 @@ extern long callback_read(long channel, long count, const char *buf, long lbn);
 extern long callback_getenv(long id, const char *buf, unsigned long buf_size);
 extern long callback_setenv(long id, const char *buf, unsigned long buf_size);
 extern long callback_save_env(void);
+extern long callback_cfgtree(long func, unsigned long arg1, unsigned long arg2,
+			     unsigned long arg3, unsigned long arg4);
 
 extern int srm_fixup(unsigned long new_callback_addr,
 		     unsigned long new_hwrpb_addr);
diff --git a/arch/alpha/include/asm/marvel_env.h b/arch/alpha/include/asm/marvel_env.h
new file mode 100644
index 000000000000..583dca6c02d1
--- /dev/null
+++ b/arch/alpha/include/asm/marvel_env.h
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ALPHA_MARVEL_ENV_H
+#define __ALPHA_MARVEL_ENV_H
+
+/*
+ * Ask the console to refresh the environmental readings of the GCT node at
+ * @offset from the start of the GCT. Returns the console status, which is 1
+ * or -0x4a on success, or -ENODEV when not booted from SRM.
+ */
+long marvel_cfgtree_partial_update(unsigned long offset);
+
+#endif /* __ALPHA_MARVEL_ENV_H */
diff --git a/arch/alpha/include/uapi/asm/console.h b/arch/alpha/include/uapi/asm/console.h
index 5fcb65300b56..ed2f0959e035 100644
--- a/arch/alpha/include/uapi/asm/console.h
+++ b/arch/alpha/include/uapi/asm/console.h
@@ -25,6 +25,8 @@
 #define CCB_GET_ENV		0x22
 #define CCB_SAVE_ENV		0x23
 
+#define CCB_CFGTREE		0x28
+
 #define CCB_PSWITCH		0x30
 #define CCB_BIOS_EMUL		0x32
 
diff --git a/arch/alpha/kernel/core_marvel.c b/arch/alpha/kernel/core_marvel.c
index 92e3312e786e..bd918028b410 100644
--- a/arch/alpha/kernel/core_marvel.c
+++ b/arch/alpha/kernel/core_marvel.c
@@ -20,10 +20,13 @@
 #include <linux/string.h>
 #include <linux/module.h>
 #include <linux/memblock.h>
+#include <linux/workqueue.h>
 
 #include <asm/ptrace.h>
 #include <asm/smp.h>
 #include <asm/gct.h>
+#include <asm/console.h>
+#include <asm/marvel_env.h>
 #include <asm/tlbflush.h>
 #include <asm/vga.h>
 
@@ -1094,3 +1097,48 @@ marvel_agp_info(void)
 
 	return agp;
 }
+
+/*
+ * The console refreshes the environmental packets of a GCT node through
+ * config tree callback function 0x1f, returning -26 while it is busy. The
+ * callback runs for up to 300 ms with interrupts disabled. Hold the console
+ * callback lock: a concurrent callback from another CPU, such as SRM console
+ * output, kills that CPU. Make the call on the boot CPU, as Tru64 UNIX does
+ * for its config tree callbacks; the PAL TOY calls also work only there.
+ */
+#define CFGTREE_PARTIAL_UPDATE	0x1f
+#define CFGTREE_BUSY		(-26)
+
+static long marvel_cfgtree_partial_update_local(void *arg)
+{
+	unsigned long flags;
+	long status;
+
+	spin_lock_irqsave(&srmcons_callback_lock, flags);
+	status = callback_cfgtree(CFGTREE_PARTIAL_UPDATE, (unsigned long)arg,
+				  0, 0, 0);
+	spin_unlock_irqrestore(&srmcons_callback_lock, flags);
+
+	return status;
+}
+
+long marvel_cfgtree_partial_update(unsigned long offset)
+{
+	long status;
+	int tries;
+
+	if (!alpha_using_srm)
+		return -ENODEV;
+
+	for (tries = 0; tries < 100; tries++) {
+		status = work_on_cpu(boot_cpuid,
+				     marvel_cfgtree_partial_update_local,
+				     (void *)offset);
+		if (status != CFGTREE_BUSY)
+			break;
+		usleep_range(10000, 20000);
+	}
+
+	return status;
+}
+EXPORT_SYMBOL_GPL(marvel_cfgtree_partial_update);
diff --git a/arch/alpha/kernel/proto.h b/arch/alpha/kernel/proto.h
index c418333d0b89..dc4ae0e0ed05 100644
--- a/arch/alpha/kernel/proto.h
+++ b/arch/alpha/kernel/proto.h
@@ -111,6 +111,7 @@ extern void * __init move_initrd(unsigned long);
 extern struct screen_info vgacon_screen_info;
 
 /* srmcons.c */
+extern spinlock_t srmcons_callback_lock;
 #if defined(CONFIG_ALPHA_GENERIC) || defined(CONFIG_ALPHA_SRM)
 extern void register_srm_console(void);
 extern void unregister_srm_console(void);
diff --git a/arch/alpha/kernel/srmcons.c b/arch/alpha/kernel/srmcons.c
index d19e51ec711d..45a10d539f19 100644
--- a/arch/alpha/kernel/srmcons.c
+++ b/arch/alpha/kernel/srmcons.c
@@ -24,7 +24,8 @@
 #include "proto.h"
 
 
-static DEFINE_SPINLOCK(srmcons_callback_lock);
+/* The console callbacks are not reentrant. */
+DEFINE_SPINLOCK(srmcons_callback_lock);
 static int srm_is_registered_console = 0;
 
 /* 
diff --git a/arch/alpha/lib/callback_srm.S b/arch/alpha/lib/callback_srm.S
index 36b63f295170..6d3c9ce6b815 100644
--- a/arch/alpha/lib/callback_srm.S
+++ b/arch/alpha/lib/callback_srm.S
@@ -94,6 +94,7 @@ CALLBACK(reset_env, CCB_RESET_ENV, 4)
 CALLBACK(save_env, CCB_SAVE_ENV, 1)
 CALLBACK(pswitch, CCB_PSWITCH, 3)
 CALLBACK(bios_emul, CCB_BIOS_EMUL, 5)
+CALLBACK(cfgtree, CCB_CFGTREE, 6)
 
 EXPORT_SYMBOL(callback_getenv)
 EXPORT_SYMBOL(callback_setenv)

-- 
2.56.1