Merge tag 'tty-4.19-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty (c284cf06) · Commits · 戴 / test

drivers/tty/hvc/hvc_console.c

+33 −5

Original line number	Diff line number	Diff line
		@@ -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)
		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;
		read_total = n;

		out:
		/* Wakeup write queue if necessary */

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