powerpc/powernv: implement opal_put_chars_atomic

The RAW console does not need writes to be atomic, so relax
opal_put_chars to be able to do partial writes, and implement an
_atomic variant which does not take a spinlock. This API is used
in xmon, so the less locking that is used, the better chance there
is that a crash can be debugged.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
index 33ab95a4ac0f1eb8e6f3ca2d7cea0aa03283db9a..cd1acc8be8ee94536d2a62a2560bf14475018057 100644 (file)
--- a/arch/powerpc/include/asm/opal.h
+++ b/arch/powerpc/include/asm/opal.h
@@ -305,6 +305,7 @@ extern void opal_configure_cores(void);
 
 extern int opal_get_chars(uint32_t vtermno, char *buf, int count);
 extern int opal_put_chars(uint32_t vtermno, const char *buf, int total_len);
+extern int opal_put_chars_atomic(uint32_t vtermno, const char *buf, int total_len);
 extern int opal_flush_console(uint32_t vtermno);
 
 extern void hvc_opal_init_early(void);

diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
index cf02e602237a32894670a2ab8a785416533c9c10..6405b6f20193ce462b9f2bfd914da853addef63f 100644 (file)
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -344,9 +344,9 @@ int opal_get_chars(uint32_t vtermno, char *buf, int count)
        return 0;
 }
 
-int opal_put_chars(uint32_t vtermno, const char *data, int total_len)
+static int __opal_put_chars(uint32_t vtermno, const char *data, int total_len, bool atomic)
 {
-       unsigned long flags;
+       unsigned long flags = 0 /* shut up gcc */;
        int written;
        __be64 olen;
        s64 rc;
@@ -354,11 +354,8 @@ int opal_put_chars(uint32_t vtermno, const char *data, int total_len)
        if (!opal.entry)
                return -ENODEV;
 
-       /* We want put_chars to be atomic to avoid mangling of hvsi
-        * packets. To do that, we first test for room and return
-        * -EAGAIN if there isn't enough.
-        */
-       spin_lock_irqsave(&opal_write_lock, flags);
+       if (atomic)
+               spin_lock_irqsave(&opal_write_lock, flags);
        rc = opal_console_write_buffer_space(vtermno, &olen);
        if (rc || be64_to_cpu(olen) < total_len) {
                /* Closed -> drop characters */
@@ -391,14 +388,18 @@ int opal_put_chars(uint32_t vtermno, const char *data, int total_len)
 
        written = be64_to_cpu(olen);
        if (written < total_len) {
-               /* Should not happen */
-               pr_warn("atomic console write returned partial len=%d written=%d\n", total_len, written);
+               if (atomic) {
+                       /* Should not happen */
+                       pr_warn("atomic console write returned partial "
+                               "len=%d written=%d\n", total_len, written);
+               }
                if (!written)
                        written = -EAGAIN;
        }
 
 out:
-       spin_unlock_irqrestore(&opal_write_lock, flags);
+       if (atomic)
+               spin_unlock_irqrestore(&opal_write_lock, flags);
 
        /* In the -EAGAIN case, callers loop, so we have to flush the console
         * here in case they have interrupts off (and we don't want to wait
@@ -412,6 +413,22 @@ out:
        return written;
 }
 
+int opal_put_chars(uint32_t vtermno, const char *data, int total_len)
+{
+       return __opal_put_chars(vtermno, data, total_len, false);
+}
+
+/*
+ * opal_put_chars_atomic will not perform partial-writes. Data will be
+ * atomically written to the terminal or not at all. This is not strictly
+ * true at the moment because console space can race with OPAL's console
+ * writes.
+ */
+int opal_put_chars_atomic(uint32_t vtermno, const char *data, int total_len)
+{
+       return __opal_put_chars(vtermno, data, total_len, true);
+}
+
 int opal_flush_console(uint32_t vtermno)
 {
        s64 rc;

diff --git a/drivers/tty/hvc/hvc_opal.c b/drivers/tty/hvc/hvc_opal.c
index 958c61c8f35a3542ad70d36cc13b3002e78b1a1a..810fd42904c3d45388d6817fa85b2b58095660b5 100644 (file)
--- a/drivers/tty/hvc/hvc_opal.c
+++ b/drivers/tty/hvc/hvc_opal.c
@@ -183,9 +183,15 @@ static int hvc_opal_probe(struct platform_device *dev)
                        return -ENOMEM;
                pv->proto = proto;
                hvc_opal_privs[termno] = pv;
-               if (proto == HV_PROTOCOL_HVSI)
-                       hvsilib_init(&pv->hvsi, opal_get_chars, opal_put_chars,
+               if (proto == HV_PROTOCOL_HVSI) {
+                       /*
+                        * We want put_chars to be atomic to avoid mangling of
+                        * hvsi packets.
+                        */
+                       hvsilib_init(&pv->hvsi,
+                                    opal_get_chars, opal_put_chars_atomic,
                                     termno, 0);
+               }
 
                /* Instanciate now to establish a mapping index==vtermno */
                hvc_instantiate(termno, termno, ops);
@@ -375,8 +381,9 @@ void __init hvc_opal_init_early(void)
        else if (of_device_is_compatible(stdout_node,"ibm,opal-console-hvsi")) {
                hvc_opal_boot_priv.proto = HV_PROTOCOL_HVSI;
                ops = &hvc_opal_hvsi_ops;
-               hvsilib_init(&hvc_opal_boot_priv.hvsi, opal_get_chars,
-                            opal_put_chars, index, 1);
+               hvsilib_init(&hvc_opal_boot_priv.hvsi,
+                            opal_get_chars, opal_put_chars_atomic,
+                            index, 1);
                /* HVSI, perform the handshake now */
                hvsilib_establish(&hvc_opal_boot_priv.hvsi);
                pr_devel("hvc_opal: Found HVSI console\n");
@@ -408,7 +415,8 @@ void __init udbg_init_debug_opal_hvsi(void)
        hvc_opal_privs[index] = &hvc_opal_boot_priv;
        hvc_opal_boot_termno = index;
        udbg_init_opal_common();
-       hvsilib_init(&hvc_opal_boot_priv.hvsi, opal_get_chars, opal_put_chars,
+       hvsilib_init(&hvc_opal_boot_priv.hvsi,
+                    opal_get_chars, opal_put_chars_atomic,
                     index, 1);
        hvsilib_establish(&hvc_opal_boot_priv.hvsi);
 }