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From: Anton Vorontsov <anton.vorontsov@linaro.org>
To: Russell King <linux@arm.linux.org.uk>,
	Jason Wessel <jason.wessel@windriver.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Alan Cox <alan@linux.intel.com>
Cc: "Arve Hjønnevåg" <arve@android.com>,
	"Colin Cross" <ccross@android.com>,
	"John Stultz" <john.stultz@linaro.org>,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linaro-kernel@lists.linaro.org, patches@linaro.org,
	kernel-team@android.com, kgdb-bugreport@lists.sourceforge.net
Subject: [PATCH 05/12] tty/serial/amba-pl011: Implement poll_init callback
Date: Mon, 20 Aug 2012 07:47:23 -0700	[thread overview]
Message-ID: <1345474050-8339-5-git-send-email-anton.vorontsov@linaro.org> (raw)
In-Reply-To: <20120820144449.GA32560@lizard>

The callback is used to initialize the hardware, nothing else should be
done, i.e. we should not request interrupts (but we can and do unmask
some of them, as they might be useful for NMI entry).

As a side-effect, the patch also fixes a division by zero[1] when booting
with kgdboc options specified (e.g. kgdboc=ttyAMA0,115200n8). The issue
happens because serial core calls set_termios callback, but the driver
doesn't know clock frequency, and thus cannot calculate proper baud rate
values.

[1]
WARNING: at drivers/tty/serial/serial_core.c:400 uart_get_baud_rate+0xe8/0x14c()
Modules linked in:
[<c0018e50>] (unwind_backtrace+0x0/0xf0) from [<c0020ae8>] (warn_slowpath_common+0x4c/0x64)
[<c0020ae8>] (warn_slowpath_common+0x4c/0x64) from [<c0020b1c>] (warn_slowpath_null+0x1c/0x24)
[<c0020b1c>] (warn_slowpath_null+0x1c/0x24) from [<c0185ed8>] (uart_get_baud_rate+0xe8/0x14c)
[<c0185ed8>] (uart_get_baud_rate+0xe8/0x14c) from [<c0187078>] (pl011_set_termios+0x48/0x278)
[<c0187078>] (pl011_set_termios+0x48/0x278) from [<c01850b0>] (uart_set_options+0xe8/0x114)
[<c01850b0>] (uart_set_options+0xe8/0x114) from [<c0185de4>] (uart_poll_init+0xd4/0xe0)
[<c0185de4>] (uart_poll_init+0xd4/0xe0) from [<c016da8c>] (tty_find_polling_driver+0x100/0x17c)
[<c016da8c>] (tty_find_polling_driver+0x100/0x17c) from [<c0188538>] (configure_kgdboc+0xc8/0x1b8)
[<c0188538>] (configure_kgdboc+0xc8/0x1b8) from [<c00088a4>] (do_one_initcall+0x30/0x168)
[<c00088a4>] (do_one_initcall+0x30/0x168) from [<c033784c>] (do_basic_setup+0x94/0xc8)
[<c033784c>] (do_basic_setup+0x94/0xc8) from [<c03378e0>] (kernel_init+0x60/0xf4)
[<c03378e0>] (kernel_init+0x60/0xf4) from [<c00144a0>] (kernel_thread_exit+0x0/0x8)
---[ end trace 7d41c9186f342c40 ]---
Division by zero in kernel.
[<c0018e50>] (unwind_backtrace+0x0/0xf0) from [<c014546c>] (Ldiv0+0x8/0x10)
[<c014546c>] (Ldiv0+0x8/0x10) from [<c0187098>] (pl011_set_termios+0x68/0x278)
[<c0187098>] (pl011_set_termios+0x68/0x278) from [<c01850b0>] (uart_set_options+0xe8/0x114)
[<c01850b0>] (uart_set_options+0xe8/0x114) from [<c0185de4>] (uart_poll_init+0xd4/0xe0)
[<c0185de4>] (uart_poll_init+0xd4/0xe0) from [<c016da8c>] (tty_find_polling_driver+0x100/0x17c)
[<c016da8c>] (tty_find_polling_driver+0x100/0x17c) from [<c0188538>] (configure_kgdboc+0xc8/0x1b8)
[<c0188538>] (configure_kgdboc+0xc8/0x1b8) from [<c00088a4>] (do_one_initcall+0x30/0x168)
[<c00088a4>] (do_one_initcall+0x30/0x168) from [<c033784c>] (do_basic_setup+0x94/0xc8)
[<c033784c>] (do_basic_setup+0x94/0xc8) from [<c03378e0>] (kernel_init+0x60/0xf4)
[<c03378e0>] (kernel_init+0x60/0xf4) from [<c00144a0>] (kernel_thread_exit+0x0/0x8)
Division by zero in kernel.
[<c0018e50>] (unwind_backtrace+0x0/0xf0) from [<c014546c>] (Ldiv0+0x8/0x10)
[<c014546c>] (Ldiv0+0x8/0x10) from [<c0183a98>] (uart_update_timeout+0x4c/0x5c)
[<c0183a98>] (uart_update_timeout+0x4c/0x5c) from [<c01870f8>] (pl011_set_termios+0xc8/0x278)
[<c01870f8>] (pl011_set_termios+0xc8/0x278) from [<c01850b0>] (uart_set_options+0xe8/0x114)
[<c01850b0>] (uart_set_options+0xe8/0x114) from [<c0185de4>] (uart_poll_init+0xd4/0xe0)
[<c0185de4>] (uart_poll_init+0xd4/0xe0) from [<c016da8c>] (tty_find_polling_driver+0x100/0x17c)
[<c016da8c>] (tty_find_polling_driver+0x100/0x17c) from [<c0188538>] (configure_kgdboc+0xc8/0x1b8)
[<c0188538>] (configure_kgdboc+0xc8/0x1b8) from [<c00088a4>] (do_one_initcall+0x30/0x168)
[<c00088a4>] (do_one_initcall+0x30/0x168) from [<c033784c>] (do_basic_setup+0x94/0xc8)
[<c033784c>] (do_basic_setup+0x94/0xc8) from [<c03378e0>] (kernel_init+0x60/0xf4)
[<c03378e0>] (kernel_init+0x60/0xf4) from [<c00144a0>] (kernel_thread_exit+0x0/0x8)

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
---
 drivers/tty/serial/amba-pl011.c | 47 ++++++++++++++++++++++++++++++-----------
 1 file changed, 35 insertions(+), 12 deletions(-)

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index d3553b5..90f2302 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -1310,10 +1310,9 @@ static void pl010_put_poll_char(struct uart_port *port,
 
 #endif /* CONFIG_CONSOLE_POLL */
 
-static int pl011_startup(struct uart_port *port)
+static int pl011_hwinit(struct uart_port *port)
 {
 	struct uart_amba_port *uap = (struct uart_amba_port *)port;
-	unsigned int cr;
 	int retval;
 
 	/* Optionaly enable pins to be muxed in and configured */
@@ -1342,6 +1341,39 @@ static int pl011_startup(struct uart_port *port)
 	       UART011_RTIS | UART011_RXIS, uap->port.membase + UART011_ICR);
 
 	/*
+	 * Save interrupts enable mask, and enable RX interrupts in case if
+	 * the interrupt is used for NMI entry.
+	 */
+	uap->im = readw(uap->port.membase + UART011_IMSC);
+	writew(UART011_RTIM | UART011_RXIM, uap->port.membase + UART011_IMSC);
+
+	if (uap->port.dev->platform_data) {
+		struct amba_pl011_data *plat;
+
+		plat = uap->port.dev->platform_data;
+		if (plat->init)
+			plat->init();
+	}
+	return 0;
+clk_unprep:
+	clk_unprepare(uap->clk);
+out:
+	return retval;
+}
+
+static int pl011_startup(struct uart_port *port)
+{
+	struct uart_amba_port *uap = (struct uart_amba_port *)port;
+	unsigned int cr;
+	int retval;
+
+	retval = pl011_hwinit(port);
+	if (retval)
+		goto clk_dis;
+
+	writew(uap->im, uap->port.membase + UART011_IMSC);
+
+	/*
 	 * Allocate the IRQ
 	 */
 	retval = request_irq(uap->port.irq, pl011_int, 0, "uart-pl011", uap);
@@ -1400,21 +1432,11 @@ static int pl011_startup(struct uart_port *port)
 	writew(uap->im, uap->port.membase + UART011_IMSC);
 	spin_unlock_irq(&uap->port.lock);
 
-	if (uap->port.dev->platform_data) {
-		struct amba_pl011_data *plat;
-
-		plat = uap->port.dev->platform_data;
-		if (plat->init)
-			plat->init();
-	}
-
 	return 0;
 
  clk_dis:
 	clk_disable(uap->clk);
- clk_unprep:
 	clk_unprepare(uap->clk);
- out:
 	return retval;
 }
 
@@ -1696,6 +1718,7 @@ static struct uart_ops amba_pl011_pops = {
 	.config_port	= pl010_config_port,
 	.verify_port	= pl010_verify_port,
 #ifdef CONFIG_CONSOLE_POLL
+	.poll_init	= pl011_hwinit,
 	.poll_get_char = pl010_get_poll_char,
 	.poll_put_char = pl010_put_poll_char,
 #endif
-- 
1.7.11.5


  parent reply	other threads:[~2012-08-20 14:53 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-08-20 14:44 [PATCH v4 0/12] KGDB/KDB FIQ (NMI) debugger Anton Vorontsov
2012-08-20 14:47 ` [PATCH 01/12] kernel/debug: Mask KGDB NMI upon entry Anton Vorontsov
2012-08-20 14:47 ` [PATCH 02/12] kdb: Implement disable_nmi command Anton Vorontsov
2012-08-20 14:47 ` [PATCH 03/12] kdb: Turn KGDB_KDB=n stubs into static inlines Anton Vorontsov
2012-08-20 14:47 ` [PATCH 04/12] tty/serial/core: Introduce poll_init callback Anton Vorontsov
2012-08-20 14:47 ` Anton Vorontsov [this message]
2012-08-20 14:47 ` [PATCH 06/12] tty/serial/kgdboc: Add and wire up clear_irqs callback Anton Vorontsov
2012-08-20 14:47 ` [PATCH 07/12] tty/serial/amba-pl011: Implement " Anton Vorontsov
2012-08-20 14:47 ` [PATCH 08/12] tty/serial: Add kgdb_nmi driver Anton Vorontsov
2012-08-20 14:47 ` [PATCH 09/12] ARM: Move some macros from entry-armv to entry-header Anton Vorontsov
2012-08-20 14:47 ` [PATCH 10/12] ARM: Add KGDB/KDB FIQ debugger generic code Anton Vorontsov
2012-08-20 14:47 ` [PATCH 11/12] ARM: VIC: Add a couple of low-level FIQ management helpers Anton Vorontsov
2012-08-20 14:47 ` [PATCH 12/12] ARM: versatile: Make able to use UART ports for KGDB FIQ debugger Anton Vorontsov
2012-08-20 20:51 ` [PATCH v4 0/12] KGDB/KDB FIQ (NMI) debugger Brian Swetland
2012-08-20 21:24   ` Anton Vorontsov
2012-09-11  9:30 [PATCH v6 " Anton Vorontsov
2012-09-11  9:34 ` [PATCH 05/12] tty/serial/amba-pl011: Implement poll_init callback Anton Vorontsov

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