ARM: 9480/1: entry: expand comment in __switch_tografted

As per discussion between the developers in the mail thread
linked, expand the comment in __switch_to so that readers
of the code understand what is going on.

Suggested-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

1 files changed, 40 insertions, 0 deletions

diff --git a/drivers/accessibility/speakup/serialio.h b/drivers/accessibility/speakup/serialio.h
new file mode 100644
index 000000000..b4f9a1925
--- /dev/null
+++ b/drivers/accessibility/speakup/serialio.h
@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _SPEAKUP_SERIAL_H
+#define _SPEAKUP_SERIAL_H
+
+#include <linux/serial.h>	/* for rs_table, serial constants */
+#include <linux/serial_reg.h>	/* for more serial constants */
+#include <linux/serial_core.h>
+
+#include "spk_priv.h"
+
+/*
+ * this is cut&paste from 8250.h. Get rid of the structure, the definitions
+ * and this whole broken driver.
+ */
+struct old_serial_port {
+	unsigned int uart; /* unused */
+	unsigned int baud_base;
+	unsigned int port;
+	unsigned int irq;
+	upf_t flags; /* unused */
+};
+
+/* countdown values for serial timeouts in us */
+#define SPK_SERIAL_TIMEOUT SPK_SYNTH_TIMEOUT
+/* countdown values transmitter/dsr timeouts in us */
+#define SPK_XMITR_TIMEOUT 100000
+/* countdown values cts timeouts in us */
+#define SPK_CTS_TIMEOUT 100000
+/* check ttyS0 ... ttyS3 */
+#define SPK_LO_TTY 0
+#define SPK_HI_TTY 3
+/* # of timeouts permitted before disable */
+#define NUM_DISABLE_TIMEOUTS 3
+/* buffer timeout in ms */
+#define SPK_TIMEOUT 100
+
+#define spk_serial_tx_busy() \
+	(!uart_lsr_tx_empty(inb(speakup_info.port_tts + UART_LSR)))
+
+#endif