From: Douglas Anderson <dianders@chromium.org>
To: jason.wessel@windriver.com, daniel.thompson@linaro.org,
gregkh@linuxfoundation.org
Cc: hpa@zytor.com, kgdb-bugreport@lists.sourceforge.net,
corbet@lwn.net, frowand.list@gmail.com, tglx@linutronix.de,
jslaby@suse.com, linux-serial@vger.kernel.org, mingo@redhat.com,
will@kernel.org, bjorn.andersson@linaro.org, agross@kernel.org,
bp@alien8.de, catalin.marinas@arm.com,
Douglas Anderson <dianders@chromium.org>,
linux-kernel@vger.kernel.org
Subject: [PATCH 7/7] serial: 8250_early: Support earlycon_kgdboc
Date: Fri, 10 Apr 2020 15:17:26 -0700 [thread overview]
Message-ID: <20200410151632.7.I8f668556c244776523320a95b09373a86eda11b7@changeid> (raw)
In-Reply-To: <20200410221726.36442-1-dianders@chromium.org>
Implement the read() function in the early console driver. With
recent kgdb patches this allows you to use kgdb to debug fairly early
into the system boot.
We only bother implementing this if polling is enabled since kgdb
can't be enabled without that.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
---
drivers/tty/serial/8250/8250_early.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c
index 5cd8c36c8fcc..70d7826788f5 100644
--- a/drivers/tty/serial/8250/8250_early.c
+++ b/drivers/tty/serial/8250/8250_early.c
@@ -109,6 +109,28 @@ static void early_serial8250_write(struct console *console,
uart_console_write(port, s, count, serial_putc);
}
+#ifdef CONFIG_CONSOLE_POLL
+static int early_serial8250_read(struct console *console,
+ char *s, unsigned int count)
+{
+ struct earlycon_device *device = console->data;
+ struct uart_port *port = &device->port;
+ unsigned int status;
+ int num_read = 0;
+
+ while (num_read < count) {
+ status = serial8250_early_in(port, UART_LSR);
+ if (!(status & UART_LSR_DR))
+ break;
+ s[num_read++] = serial8250_early_in(port, UART_RX);
+ }
+
+ return num_read;
+}
+#else
+#define early_serial8250_read NULL
+#endif
+
static void __init init_port(struct earlycon_device *device)
{
struct uart_port *port = &device->port;
@@ -149,6 +171,7 @@ int __init early_serial8250_setup(struct earlycon_device *device,
init_port(device);
device->con->write = early_serial8250_write;
+ device->con->read = early_serial8250_read;
return 0;
}
EARLYCON_DECLARE(uart8250, early_serial8250_setup);
--
2.26.0.110.g2183baf09c-goog
prev parent reply other threads:[~2020-04-10 22:18 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-10 22:17 [PATCH 0/7] kgdb: Support late serial drivers; enable early debug w/ boot consoles Douglas Anderson
2020-04-10 22:17 ` [PATCH 1/7] kgdboc: Use a platform device to handle tty drivers showing up late Douglas Anderson
2020-04-10 22:17 ` [PATCH 2/7] kgdb: Delay "kgdbwait" to dbg_late_init() by default Douglas Anderson
2020-04-10 22:17 ` [PATCH 3/7] arm64: Add call_break_hook() to early_brk64() for early kgdb Douglas Anderson
2020-04-10 22:17 ` [PATCH 4/7] kgdboc: Add earlycon_kgdboc to support early kgdb using boot consoles Douglas Anderson
2020-04-10 23:56 ` kbuild test robot
2020-04-13 21:59 ` Doug Anderson
2020-04-11 1:44 ` kbuild test robot
2020-04-10 22:17 ` [PATCH 5/7] Documentation: kgdboc: Document new earlycon_kgdboc parameter Douglas Anderson
2020-04-10 22:17 ` [PATCH 6/7] serial: qcom_geni_serial: Support earlycon_kgdboc Douglas Anderson
2020-04-10 22:17 ` Douglas Anderson [this message]
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