From: "Maciej W. Rozycki" <macro@linux-mips.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mips@linux-mips.org, linux-serial@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: [PATCH] zs.c: Drain the transmission line
Date: Wed, 6 Jun 2007 10:07:34 +0100 (BST) [thread overview]
Message-ID: <Pine.LNX.4.64N.0706051145260.15653@blysk.ds.pg.gda.pl> (raw)
This is an update to the zs.c driver to make it wait for the transmission
line to become idle before disabling the transmitter or resetting the
chip. This way the character that is on the way at the time one of these
actions is about to be performed does not get corrupted.
Plus a change to reset the index/data pointer first before issuing a chip
reset just in case the state is wrong when control of the chip is taken
the first time.
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
---
These are almost obvious, but I have run-time tested them just in case.
They make the switch from the initial (early printk) PROM-based console
less disruptive. The change to load_zsregs() also affects set_termios().
Please apply,
Maciej
patch-mips-2.6.21-20070502-zs-serial-drain-3
diff -up --recursive --new-file linux-mips-2.6.21-20070502.macro/drivers/serial/zs.c linux-mips-2.6.21-20070502/drivers/serial/zs.c
--- linux-mips-2.6.21-20070502.macro/drivers/serial/zs.c 2007-06-05 11:08:24.000000000 +0000
+++ linux-mips-2.6.21-20070502/drivers/serial/zs.c 2007-06-05 11:08:57.000000000 +0000
@@ -240,10 +240,24 @@ static int zs_transmit_drain(struct zs_p
return loops;
}
+static int zs_line_drain(struct zs_port *zport, int irq)
+{
+ struct zs_scc *scc = zport->scc;
+ int loops = 10000;
+
+ while (!(read_zsreg(zport, R1) & ALL_SNT) && loops--) {
+ zs_spin_unlock_cond_irq(&scc->zlock, irq);
+ udelay(2);
+ zs_spin_lock_cond_irq(&scc->zlock, irq);
+ }
+ return loops;
+}
+
static void load_zsregs(struct zs_port *zport, u8 *regs, int irq)
{
- zs_transmit_drain(zport, irq);
+ /* Let the current transmission finish. */
+ zs_line_drain(zport, irq);
/* Load 'em up. */
write_zsreg(zport, R3, regs[3] & ~RxENABLE);
write_zsreg(zport, R5, regs[5] & ~TxENAB);
@@ -814,6 +828,10 @@ static void zs_reset(struct zs_port *zpo
spin_lock_irqsave(&scc->zlock, flags);
irq = !irqs_disabled_flags(flags);
if (!scc->initialised) {
+ /* Reset the pointer first, just in case... */
+ read_zsreg(zport, R0);
+ /* And let the current transmission finish. */
+ zs_line_drain(zport, irq);
write_zsreg(zport, R9, FHWRES);
udelay(10);
write_zsreg(zport, R9, 0);
reply other threads:[~2007-06-06 9:07 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=Pine.LNX.4.64N.0706051145260.15653@blysk.ds.pg.gda.pl \
--to=macro@linux-mips.org \
--cc=akpm@linux-foundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mips@linux-mips.org \
--cc=linux-serial@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).