Merge tag 'asoc-v5.0' of https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound into for-linus

ASoC: Updates for v5.0/v4.20

As ever there's a lot of small and driver specific changes going on
here, but we do also have some relatively large changes in the core
thanks to the hard work of Charles and Morimoto-san:

 - More component transitions from Morimoto-san, I think we're about
   finished with this.  Thanks for all the hard work!
 - Morimoto-san also added a bunch of for_each_foo macros
 - A bunch of cleanups and fixes for DAPM from Charles.
 - MCLK support for several different devices, including CS42L51, STM32
   SAI, and MAX98373.
 - Support for Allwinner A64 CODEC analog, Intel boards with DA7219 and
   MAX98927, Meson AXG PDM inputs, Nuvoton NAU8822, Renesas R8A7744 and
   TI PCM3060.

1 files changed, 33 insertions, 5 deletions

diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
index 5414c4a87bea..27284a2dcd2b 100644
--- a/drivers/tty/hvc/hvc_console.c
+++ b/drivers/tty/hvc/hvc_console.c
@@ -522,6 +522,8 @@ static int hvc_write(struct tty_struct *tty, const unsigned char *buf, int count
 		return -EIO;
 
 	while (count > 0) {
+		int ret = 0;
+
 		spin_lock_irqsave(&hp->lock, flags);
 
 		rsize = hp->outbuf_size - hp->n_outbuf;
@@ -537,10 +539,13 @@ static int hvc_write(struct tty_struct *tty, const unsigned char *buf, int count
 		}
 
 		if (hp->n_outbuf > 0)
-			hvc_push(hp);
+			ret = hvc_push(hp);
 
 		spin_unlock_irqrestore(&hp->lock, flags);
 
+		if (!ret)
+			break;
+
 		if (count) {
 			if (hp->n_outbuf > 0)
 				hvc_flush(hp);
@@ -623,6 +628,15 @@ static int hvc_chars_in_buffer(struct tty_struct *tty)
 #define MAX_TIMEOUT		(2000)
 static u32 timeout = MIN_TIMEOUT;
 
+/*
+ * Maximum number of bytes to get from the console driver if hvc_poll is
+ * called from driver (and can't sleep). Any more than this and we break
+ * and start polling with khvcd. This value was derived from from an OpenBMC
+ * console with the OPAL driver that results in about 0.25ms interrupts off
+ * latency.
+ */
+#define HVC_ATOMIC_READ_MAX	128
+
 #define HVC_POLL_READ	0x00000001
 #define HVC_POLL_WRITE	0x00000002
 
@@ -669,8 +683,8 @@ static int __hvc_poll(struct hvc_struct *hp, bool may_sleep)
 	if (!hp->irq_requested)
 		poll_mask |= HVC_POLL_READ;
 
+ read_again:
 	/* Read data if any */
-
 	count = tty_buffer_request_room(&hp->port, N_INBUF);
 
 	/* If flip is full, just reschedule a later read */
@@ -717,9 +731,23 @@ static int __hvc_poll(struct hvc_struct *hp, bool may_sleep)
 #endif /* CONFIG_MAGIC_SYSRQ */
 		tty_insert_flip_char(&hp->port, buf[i], 0);
 	}
-	if (n == count)
-		poll_mask |= HVC_POLL_READ;
-	read_total = n;
+	read_total += n;
+
+	if (may_sleep) {
+		/* Keep going until the flip is full */
+		spin_unlock_irqrestore(&hp->lock, flags);
+		cond_resched();
+		spin_lock_irqsave(&hp->lock, flags);
+		goto read_again;
+	} else if (read_total < HVC_ATOMIC_READ_MAX) {
+		/* Break and defer if it's a large read in atomic */
+		goto read_again;
+	}
+
+	/*
+	 * Latency break, schedule another poll immediately.
+	 */
+	poll_mask |= HVC_POLL_READ;
 
  out:
 	/* Wakeup write queue if necessary */