[PATCH] serial: samsung: Add samsung_early_read to support early kgdboc

From: Woody Lin
Date: Wed Mar 02 2022 - 05:20:05 EST


The 'kgdboc_earlycon_init' looks for boot console that has both .read
and .write callbacks. Adds 'samsung_early_read' to samsung_tty.c's early
console to support kgdboc.

Signed-off-by: Woody Lin <woodylin@xxxxxxxxxx>
---
drivers/tty/serial/samsung_tty.c | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)

diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
index d002a4e48ed9..eeb30d016ff1 100644
--- a/drivers/tty/serial/samsung_tty.c
+++ b/drivers/tty/serial/samsung_tty.c
@@ -2949,6 +2949,7 @@ static void wr_reg_barrier(struct uart_port *port, u32 reg, u32 val)

struct samsung_early_console_data {
u32 txfull_mask;
+ u32 rxfifo_mask;
};

static void samsung_early_busyuart(struct uart_port *port)
@@ -2983,6 +2984,26 @@ static void samsung_early_write(struct console *con, const char *s,
uart_console_write(&dev->port, s, n, samsung_early_putc);
}

+static int samsung_early_read(struct console *con, char *s, unsigned int n)
+{
+ struct earlycon_device *dev = con->data;
+ struct samsung_early_console_data *data = dev->port.private_data;
+ int ch, ufstat, num_read = 0;
+
+ while (num_read < n) {
+ ufstat = rd_regl(&dev->port, S3C2410_UFSTAT);
+ if (!(ufstat & data->rxfifo_mask))
+ break;
+ ch = rd_reg(&dev->port, S3C2410_URXH);
+ if (ch == NO_POLL_CHAR)
+ break;
+
+ s[num_read++] = ch;
+ }
+
+ return num_read;
+}
+
static int __init samsung_early_console_setup(struct earlycon_device *device,
const char *opt)
{
@@ -2990,12 +3011,14 @@ static int __init samsung_early_console_setup(struct earlycon_device *device,
return -ENODEV;

device->con->write = samsung_early_write;
+ device->con->read = samsung_early_read;
return 0;
}

/* S3C2410 */
static struct samsung_early_console_data s3c2410_early_console_data = {
.txfull_mask = S3C2410_UFSTAT_TXFULL,
+ .rxfifo_mask = S3C2410_UFSTAT_RXFULL | S3C2410_UFSTAT_RXMASK,
};

static int __init s3c2410_early_console_setup(struct earlycon_device *device,
@@ -3011,6 +3034,7 @@ OF_EARLYCON_DECLARE(s3c2410, "samsung,s3c2410-uart",
/* S3C2412, S3C2440, S3C64xx */
static struct samsung_early_console_data s3c2440_early_console_data = {
.txfull_mask = S3C2440_UFSTAT_TXFULL,
+ .rxfifo_mask = S3C2440_UFSTAT_RXFULL | S3C2440_UFSTAT_RXMASK,
};

static int __init s3c2440_early_console_setup(struct earlycon_device *device,
@@ -3030,6 +3054,7 @@ OF_EARLYCON_DECLARE(s3c6400, "samsung,s3c6400-uart",
/* S5PV210, Exynos */
static struct samsung_early_console_data s5pv210_early_console_data = {
.txfull_mask = S5PV210_UFSTAT_TXFULL,
+ .rxfifo_mask = S5PV210_UFSTAT_RXFULL | S5PV210_UFSTAT_RXMASK,
};

static int __init s5pv210_early_console_setup(struct earlycon_device *device,
--
2.35.1.574.g5d30c73bfb-goog