[PATCH v2 22/25] tty: serial: samsung_tty: Add support for Apple UARTs

Hector Martin
2021-02-15T12:24:35Z

Apple SoCs are a distant descendant of Samsung designs and use yet
another variant of their UART style, with different interrupt handling.

In particular, this variant has the following differences with existing
ones:

* It includes a built-in interrupt controller with different registers,
using only a single platform IRQ

* Internal interrupt sources are treated as edge-triggered, even though
the IRQ output is level-triggered. This chiefly affects the TX IRQ
path: the driver can no longer rely on the TX buffer empty IRQ
immediately firing after TX is enabled, but instead must prime the
FIFO with data directly.

Signed-off-by: Hector Martin <marcan@marcan.st>
---
drivers/tty/serial/Kconfig | 2 +-
drivers/tty/serial/samsung_tty.c | 228 +++++++++++++++++++++++++++++--
include/linux/serial_s3c.h | 16 +++
3 files changed, 236 insertions(+), 10 deletions(-)

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 34a2899e69c0..9bfe4ec1e761 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -236,7 +236,7 @@ config SERIAL_CLPS711X_CONSOLE

config SERIAL_SAMSUNG
tristate "Samsung SoC serial support"
- depends on PLAT_SAMSUNG || ARCH_S5PV210 || ARCH_EXYNOS || COMPILE_TEST
+ depends on PLAT_SAMSUNG || ARCH_S5PV210 || ARCH_EXYNOS || ARCH_APPLE || COMPILE_TEST
select SERIAL_CORE
help
Support for the on-chip UARTs on the Samsung S3C24XX series CPUs,
diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
index 619bc4864e2a..e7ab0b9d89a7 100644
--- a/drivers/tty/serial/samsung_tty.c
+++ b/drivers/tty/serial/samsung_tty.c
@@ -59,6 +59,7 @@
enum s3c24xx_port_type {
TYPE_S3C24XX,
TYPE_S3C6400,
+ TYPE_APPLE_S5L,
};

struct s3c24xx_uart_info {
@@ -290,6 +291,9 @@ static void s3c24xx_serial_stop_tx(struct uart_port *port)
return;

switch (ourport->info->type) {
+ case TYPE_APPLE_S5L:
+ s3c24xx_clear_bit(port, APPLE_S5L_UCON_TXTHRESH_ENA, S3C2410_UCON);
+ break;
case TYPE_S3C6400:
s3c24xx_set_bit(port, S3C64XX_UINTM_TXD, S3C64XX_UINTM);
break;
@@ -356,6 +360,9 @@ static void enable_tx_dma(struct s3c24xx_uart_port *ourport)

/* Mask Tx interrupt */
switch (ourport->info->type) {
+ case TYPE_APPLE_S5L:
+ WARN_ON(1); // No DMA
+ break;
case TYPE_S3C6400:
s3c24xx_set_bit(port, S3C64XX_UINTM_TXD, S3C64XX_UINTM);
break;
@@ -389,10 +396,12 @@ static void enable_tx_pio(struct s3c24xx_uart_port *ourport)
ucon = rd_regl(port, S3C2410_UCON);
ucon &= ~(S3C64XX_UCON_TXMODE_MASK);
ucon |= S3C64XX_UCON_TXMODE_CPU;
- wr_regl(port, S3C2410_UCON, ucon);

/* Unmask Tx interrupt */
switch (ourport->info->type) {
+ case TYPE_APPLE_S5L:
+ ucon |= APPLE_S5L_UCON_TXTHRESH_ENA_MSK;
+ break;
case TYPE_S3C6400:
s3c24xx_clear_bit(port, S3C64XX_UINTM_TXD, S3C64XX_UINTM);
break;
@@ -401,7 +410,16 @@ static void enable_tx_pio(struct s3c24xx_uart_port *ourport)
break;
}

+ wr_regl(port, S3C2410_UCON, ucon);
+
ourport->tx_mode = S3C24XX_TX_PIO;
+
+ /*
+ * The Apple version only has edge triggered TX IRQs, so we need
+ * to kick off the process by sending some characters here.
+ */
+ if (ourport->info->type == TYPE_APPLE_S5L)
+ s3c24xx_serial_tx_chars(ourport);
}

static void s3c24xx_serial_start_tx_pio(struct s3c24xx_uart_port *ourport)
@@ -523,6 +541,10 @@ static void s3c24xx_serial_stop_rx(struct uart_port *port)
if (ourport->rx_enabled) {
dev_dbg(port->dev, "stopping rx\n");
switch (ourport->info->type) {
+ case TYPE_APPLE_S5L:
+ s3c24xx_clear_bit(port, APPLE_S5L_UCON_RXTHRESH_ENA, S3C2410_UCON);
+ s3c24xx_clear_bit(port, APPLE_S5L_UCON_RXTO_ENA, S3C2410_UCON);
+ break;
case TYPE_S3C6400:
s3c24xx_set_bit(port, S3C64XX_UINTM_RXD, S3C64XX_UINTM);
break;
@@ -663,14 +685,18 @@ static void enable_rx_pio(struct s3c24xx_uart_port *ourport)

/* set Rx mode to DMA mode */
ucon = rd_regl(port, S3C2410_UCON);
- ucon &= ~(S3C64XX_UCON_TIMEOUT_MASK |
- S3C64XX_UCON_EMPTYINT_EN |
- S3C64XX_UCON_DMASUS_EN |
- S3C64XX_UCON_TIMEOUT_EN |
- S3C64XX_UCON_RXMODE_MASK);
- ucon |= 0xf << S3C64XX_UCON_TIMEOUT_SHIFT |
- S3C64XX_UCON_TIMEOUT_EN |
- S3C64XX_UCON_RXMODE_CPU;
+ ucon &= ~S3C64XX_UCON_RXMODE_MASK;
+ ucon |= S3C64XX_UCON_RXMODE_CPU;
+
+ /* Apple types use these bits for IRQ masks */
+ if (ourport->info->type != TYPE_APPLE_S5L) {
+ ucon &= ~(S3C64XX_UCON_TIMEOUT_MASK |
+ S3C64XX_UCON_EMPTYINT_EN |
+ S3C64XX_UCON_DMASUS_EN |
+ S3C64XX_UCON_TIMEOUT_EN);
+ ucon |= 0xf << S3C64XX_UCON_TIMEOUT_SHIFT |
+ S3C64XX_UCON_TIMEOUT_EN;
+ }
wr_regl(port, S3C2410_UCON, ucon);

ourport->rx_mode = S3C24XX_RX_PIO;
@@ -934,6 +960,27 @@ static irqreturn_t s3c64xx_serial_handle_irq(int irq, void *id)
return ret;
}

+/* interrupt handler for Apple SoC's.*/
+static irqreturn_t apple_serial_handle_irq(int irq, void *id)
+{
+ struct s3c24xx_uart_port *ourport = id;
+ struct uart_port *port = &ourport->port;
+ unsigned int pend = rd_regl(port, S3C2410_UTRSTAT);
+ irqreturn_t ret = IRQ_NONE;
+
+ if (pend & (APPLE_S5L_UTRSTAT_RXTHRESH | APPLE_S5L_UTRSTAT_RXTO)) {
+ wr_regl(port, S3C2410_UTRSTAT,
+ APPLE_S5L_UTRSTAT_RXTHRESH | APPLE_S5L_UTRSTAT_RXTO);
+ ret = s3c24xx_serial_rx_irq(irq, id);
+ }
+ if (pend & APPLE_S5L_UTRSTAT_TXTHRESH) {
+ wr_regl(port, S3C2410_UTRSTAT, APPLE_S5L_UTRSTAT_TXTHRESH);
+ ret = s3c24xx_serial_tx_irq(irq, id);
+ }
+
+ return ret;
+}
+
static unsigned int s3c24xx_serial_tx_empty(struct uart_port *port)
{
struct s3c24xx_uart_info *info = s3c24xx_port_to_info(port);
@@ -1153,6 +1200,32 @@ static void s3c64xx_serial_shutdown(struct uart_port *port)
ourport->tx_in_progress = 0;
}

+static void apple_s5l_serial_shutdown(struct uart_port *port)
+{
+ struct s3c24xx_uart_port *ourport = to_ourport(port);
+
+ unsigned int ucon;
+
+ ucon = rd_regl(port, S3C2410_UCON);
+ ucon &= ~(APPLE_S5L_UCON_TXTHRESH_ENA_MSK |
+ APPLE_S5L_UCON_RXTHRESH_ENA_MSK |
+ APPLE_S5L_UCON_RXTO_ENA_MSK);
+ wr_regl(port, S3C2410_UCON, ucon);
+
+ wr_regl(port, S3C2410_UTRSTAT, APPLE_S5L_UTRSTAT_ALL_FLAGS);
+
+ free_irq(port->irq, ourport);
+
+ ourport->tx_enabled = 0;
+ ourport->tx_mode = 0;
+ ourport->rx_enabled = 0;
+
+ if (ourport->dma)
+ s3c24xx_serial_release_dma(ourport);
+
+ ourport->tx_in_progress = 0;
+}
+
static int s3c24xx_serial_startup(struct uart_port *port)
{
struct s3c24xx_uart_port *ourport = to_ourport(port);
@@ -1240,6 +1313,45 @@ static int s3c64xx_serial_startup(struct uart_port *port)
return ret;
}

+static int apple_s5l_serial_startup(struct uart_port *port)
+{
+ struct s3c24xx_uart_port *ourport = to_ourport(port);
+ unsigned long flags;
+ unsigned int ufcon;
+ int ret;
+
+ wr_regl(port, S3C2410_UTRSTAT, APPLE_S5L_UTRSTAT_ALL_FLAGS);
+
+ ret = request_irq(port->irq, apple_serial_handle_irq, 0,
+ s3c24xx_serial_portname(port), ourport);
+ if (ret) {
+ dev_err(port->dev, "cannot get irq %d\n", port->irq);
+ return ret;
+ }
+
+ /* For compatibility with s3c24xx Soc's */
+ ourport->rx_enabled = 1;
+ ourport->tx_enabled = 0;
+
+ spin_lock_irqsave(&port->lock, flags);
+
+ ufcon = rd_regl(port, S3C2410_UFCON);
+ ufcon |= S3C2410_UFCON_RESETRX | S5PV210_UFCON_RXTRIG8;
+ if (!uart_console(port))
+ ufcon |= S3C2410_UFCON_RESETTX;
+ wr_regl(port, S3C2410_UFCON, ufcon);
+
+ enable_rx_pio(ourport);
+
+ spin_unlock_irqrestore(&port->lock, flags);
+
+ /* Enable Rx Interrupt */
+ s3c24xx_set_bit(port, APPLE_S5L_UCON_RXTHRESH_ENA, S3C2410_UCON);
+ s3c24xx_set_bit(port, APPLE_S5L_UCON_RXTO_ENA, S3C2410_UCON);
+
+ return ret;
+}
+
/* power power management control */

static void s3c24xx_serial_pm(struct uart_port *port, unsigned int level,
@@ -1567,6 +1679,8 @@ static const char *s3c24xx_serial_type(struct uart_port *port)
return "S3C24XX";
case TYPE_S3C6400:
return "S3C6400/10";
+ case TYPE_APPLE_S5L:
+ return "APPLE S5L";
default:
return NULL;
}
@@ -1658,6 +1772,27 @@ static const struct uart_ops s3c64xx_serial_ops = {
#endif
};

+static const struct uart_ops apple_s5l_serial_ops = {
+ .pm = s3c24xx_serial_pm,
+ .tx_empty = s3c24xx_serial_tx_empty,
+ .get_mctrl = s3c24xx_serial_get_mctrl,
+ .set_mctrl = s3c24xx_serial_set_mctrl,
+ .stop_tx = s3c24xx_serial_stop_tx,
+ .start_tx = s3c24xx_serial_start_tx,
+ .stop_rx = s3c24xx_serial_stop_rx,
+ .break_ctl = s3c24xx_serial_break_ctl,
+ .startup = apple_s5l_serial_startup,
+ .shutdown = apple_s5l_serial_shutdown,
+ .set_termios = s3c24xx_serial_set_termios,
+ .type = s3c24xx_serial_type,
+ .config_port = s3c24xx_serial_config_port,
+ .verify_port = s3c24xx_serial_verify_port,
+#if defined(CONFIG_SERIAL_SAMSUNG_CONSOLE) && defined(CONFIG_CONSOLE_POLL)
+ .poll_get_char = s3c24xx_serial_get_poll_char,
+ .poll_put_char = s3c24xx_serial_put_poll_char,
+#endif
+};
+
static struct uart_driver s3c24xx_uart_drv = {
.owner = THIS_MODULE,
.driver_name = "s3c2410_serial",
@@ -1969,6 +2104,18 @@ static int s3c24xx_serial_init_port(struct s3c24xx_uart_port *ourport,

/* Keep all interrupts masked and cleared */
switch (ourport->info->type) {
+ case TYPE_APPLE_S5L: {
+ unsigned int ucon;
+
+ ucon = rd_regl(port, S3C2410_UCON);
+ ucon &= ~(APPLE_S5L_UCON_TXTHRESH_ENA_MSK |
+ APPLE_S5L_UCON_RXTHRESH_ENA_MSK |
+ APPLE_S5L_UCON_RXTO_ENA_MSK);
+ wr_regl(port, S3C2410_UCON, ucon);
+
+ wr_regl(port, S3C2410_UTRSTAT, APPLE_S5L_UTRSTAT_ALL_FLAGS);
+ break;
+ }
case TYPE_S3C6400:
wr_regl(port, S3C64XX_UINTM, 0xf);
wr_regl(port, S3C64XX_UINTP, 0xf);
@@ -2053,6 +2200,9 @@ static int s3c24xx_serial_probe(struct platform_device *pdev)
case TYPE_S3C6400:
ourport->port.ops = &s3c64xx_serial_ops;
break;
+ case TYPE_APPLE_S5L:
+ ourport->port.ops = &apple_s5l_serial_ops;
+ break;
}

if (np) {
@@ -2179,6 +2329,32 @@ static int s3c24xx_serial_resume_noirq(struct device *dev)
if (port) {
/* restore IRQ mask */
switch (ourport->info->type) {
+ case TYPE_APPLE_S5L: {
+ unsigned int ucon;
+
+ clk_prepare_enable(ourport->clk);
+ if (!IS_ERR(ourport->baudclk))
+ clk_prepare_enable(ourport->baudclk);
+
+ ucon = rd_regl(port, S3C2410_UCON);
+
+ ucon &= ~(APPLE_S5L_UCON_TXTHRESH_ENA_MSK |
+ APPLE_S5L_UCON_RXTHRESH_ENA_MSK |
+ APPLE_S5L_UCON_RXTO_ENA_MSK);
+
+ if (ourport->tx_enabled)
+ ucon |= APPLE_S5L_UCON_TXTHRESH_ENA_MSK;
+ if (ourport->rx_enabled)
+ ucon |= APPLE_S5L_UCON_RXTHRESH_ENA_MSK |
+ APPLE_S5L_UCON_RXTO_ENA_MSK;
+
+ wr_regl(port, S3C2410_UCON, ucon);
+
+ if (!IS_ERR(ourport->baudclk))
+ clk_disable_unprepare(ourport->baudclk);
+ clk_disable_unprepare(ourport->clk);
+ break;
+ }
case TYPE_S3C6400: {
unsigned int uintm = 0xf;

@@ -2604,6 +2780,35 @@ static struct s3c24xx_serial_drv_data exynos5433_serial_drv_data = {
#define EXYNOS5433_SERIAL_DRV_DATA (kernel_ulong_t)NULL
#endif

+#ifdef CONFIG_ARCH_APPLE
+static struct s3c24xx_serial_drv_data s5l_serial_drv_data = {
+ .info = &(struct s3c24xx_uart_info) {
+ .name = "Apple S5L UART",
+ .type = TYPE_APPLE_S5L,
+ .port_type = PORT_8250,
+ .fifosize = 16,
+ .rx_fifomask = S3C2410_UFSTAT_RXMASK,
+ .rx_fifoshift = S3C2410_UFSTAT_RXSHIFT,
+ .rx_fifofull = S3C2410_UFSTAT_RXFULL,
+ .tx_fifofull = S3C2410_UFSTAT_TXFULL,
+ .tx_fifomask = S3C2410_UFSTAT_TXMASK,
+ .tx_fifoshift = S3C2410_UFSTAT_TXSHIFT,
+ .def_clk_sel = S3C2410_UCON_CLKSEL0,
+ .num_clks = 1,
+ .clksel_mask = 0,
+ .clksel_shift = 0,
+ },
+ .def_cfg = &(struct s3c2410_uartcfg) {
+ .ucon = APPLE_S5L_UCON_DEFAULT,
+ .ufcon = S3C2410_UFCON_DEFAULT,
+ },
+};
+#define S5L_SERIAL_DRV_DATA ((kernel_ulong_t)&s5l_serial_drv_data)
+#else
+#define S5L_SERIAL_DRV_DATA ((kernel_ulong_t)NULL)
+#endif
+
+
static const struct platform_device_id s3c24xx_serial_driver_ids[] = {
{
.name = "s3c2410-uart",
@@ -2626,6 +2831,9 @@ static const struct platform_device_id s3c24xx_serial_driver_ids[] = {
}, {
.name = "exynos5433-uart",
.driver_data = EXYNOS5433_SERIAL_DRV_DATA,
+ }, {
+ .name = "s5l-uart",
+ .driver_data = S5L_SERIAL_DRV_DATA,
},
{ },
};
@@ -2647,6 +2855,8 @@ static const struct of_device_id s3c24xx_uart_dt_match[] = {
.data = (void *)EXYNOS4210_SERIAL_DRV_DATA },
{ .compatible = "samsung,exynos5433-uart",
.data = (void *)EXYNOS5433_SERIAL_DRV_DATA },
+ { .compatible = "apple,s5l-uart",
+ .data = (void *)S5L_SERIAL_DRV_DATA },
{},
};
MODULE_DEVICE_TABLE(of, s3c24xx_uart_dt_match);
diff --git a/include/linux/serial_s3c.h b/include/linux/serial_s3c.h
index ca2c5393dc6b..f6c3323fc4c5 100644
--- a/include/linux/serial_s3c.h
+++ b/include/linux/serial_s3c.h
@@ -246,6 +246,22 @@
S5PV210_UFCON_TXTRIG4 | \
S5PV210_UFCON_RXTRIG4)

+#define APPLE_S5L_UCON_RXTO_ENA 9
+#define APPLE_S5L_UCON_RXTHRESH_ENA 12
+#define APPLE_S5L_UCON_TXTHRESH_ENA 13
+#define APPLE_S5L_UCON_RXTO_ENA_MSK (1 << APPLE_S5L_UCON_RXTO_ENA)
+#define APPLE_S5L_UCON_RXTHRESH_ENA_MSK (1 << APPLE_S5L_UCON_RXTHRESH_ENA)
+#define APPLE_S5L_UCON_TXTHRESH_ENA_MSK (1 << APPLE_S5L_UCON_TXTHRESH_ENA)
+
+#define APPLE_S5L_UCON_DEFAULT (S3C2410_UCON_TXIRQMODE | \
+ S3C2410_UCON_RXIRQMODE | \
+ S3C2410_UCON_RXFIFO_TOI)
+
+#define APPLE_S5L_UTRSTAT_RXTHRESH (1<<4)
+#define APPLE_S5L_UTRSTAT_TXTHRESH (1<<5)
+#define APPLE_S5L_UTRSTAT_RXTO (1<<9)
+#define APPLE_S5L_UTRSTAT_ALL_FLAGS (0x3f0)
+
#ifndef __ASSEMBLY__

#include <linux/serial_core.h>
--
2.30.0