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tty: serial: samsung_tty: Add support for Apple UARTs
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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>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Tested-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210304213902.83903-25-marcan@marcan.st
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Hector Martin authored and Greg Kroah-Hartman committed Mar 10, 2021
1 parent b846683 commit fcbba34
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Showing 3 changed files with 247 additions and 9 deletions.
2 changes: 1 addition & 1 deletion drivers/tty/serial/Kconfig
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Original file line number Diff line number Diff line change
Expand Up @@ -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,
Expand Down
238 changes: 230 additions & 8 deletions drivers/tty/serial/samsung_tty.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -59,6 +59,7 @@
enum s3c24xx_port_type {
TYPE_S3C24XX,
TYPE_S3C6400,
TYPE_APPLE_S5L,
};

struct s3c24xx_uart_info {
Expand Down Expand Up @@ -151,6 +152,8 @@ struct s3c24xx_uart_port {
#endif
};

static void s3c24xx_serial_tx_chars(struct s3c24xx_uart_port *ourport);

/* conversion functions */

#define s3c24xx_dev_to_port(__dev) dev_get_drvdata(__dev)
Expand Down Expand Up @@ -290,6 +293,9 @@ static void s3c24xx_serial_stop_tx(struct uart_port *port)
case TYPE_S3C6400:
s3c24xx_set_bit(port, S3C64XX_UINTM_TXD, S3C64XX_UINTM);
break;
case TYPE_APPLE_S5L:
s3c24xx_clear_bit(port, APPLE_S5L_UCON_TXTHRESH_ENA, S3C2410_UCON);
break;
default:
disable_irq_nosync(ourport->tx_irq);
break;
Expand Down Expand Up @@ -358,6 +364,9 @@ static void enable_tx_dma(struct s3c24xx_uart_port *ourport)
case TYPE_S3C6400:
s3c24xx_set_bit(port, S3C64XX_UINTM_TXD, S3C64XX_UINTM);
break;
case TYPE_APPLE_S5L:
WARN_ON(1); // No DMA
break;
default:
disable_irq_nosync(ourport->tx_irq);
break;
Expand Down Expand Up @@ -396,12 +405,23 @@ static void enable_tx_pio(struct s3c24xx_uart_port *ourport)
s3c24xx_clear_bit(port, S3C64XX_UINTM_TXD,
S3C64XX_UINTM);
break;
case TYPE_APPLE_S5L:
ucon |= APPLE_S5L_UCON_TXTHRESH_ENA_MSK;
wr_regl(port, S3C2410_UCON, ucon);
break;
default:
enable_irq(ourport->tx_irq);
break;
}

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)
Expand Down Expand Up @@ -527,6 +547,10 @@ static void s3c24xx_serial_stop_rx(struct uart_port *port)
s3c24xx_set_bit(port, S3C64XX_UINTM_RXD,
S3C64XX_UINTM);
break;
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;
default:
disable_irq_nosync(ourport->rx_irq);
break;
Expand Down Expand Up @@ -664,14 +688,18 @@ 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;
Expand Down Expand Up @@ -935,6 +963,27 @@ 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);
Expand Down Expand Up @@ -1154,6 +1203,32 @@ 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);
Expand Down Expand Up @@ -1241,6 +1316,45 @@ 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,
Expand Down Expand Up @@ -1568,6 +1682,8 @@ 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;
}
Expand Down Expand Up @@ -1659,6 +1775,27 @@ 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",
Expand Down Expand Up @@ -1975,6 +2112,18 @@ static int s3c24xx_serial_init_port(struct s3c24xx_uart_port *ourport,
wr_regl(port, S3C64XX_UINTP, 0xf);
wr_regl(port, S3C64XX_UINTSP, 0xf);
break;
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;
}
default:
break;
}
Expand Down Expand Up @@ -2054,6 +2203,9 @@ 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) {
Expand Down Expand Up @@ -2196,6 +2348,43 @@ static int s3c24xx_serial_resume_noirq(struct device *dev)
clk_disable_unprepare(ourport->clk);
break;
}
case TYPE_APPLE_S5L: {
unsigned int ucon;
int ret;

ret = clk_prepare_enable(ourport->clk);
if (ret) {
dev_err(dev, "clk_enable clk failed: %d\n", ret);
return ret;
}
if (!IS_ERR(ourport->baudclk)) {
ret = clk_prepare_enable(ourport->baudclk);
if (ret) {
dev_err(dev, "clk_enable baudclk failed: %d\n", ret);
clk_disable_unprepare(ourport->clk);
return ret;
}
}

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;
}
default:
break;
}
Expand Down Expand Up @@ -2605,6 +2794,34 @@ 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",
Expand All @@ -2627,6 +2844,9 @@ 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,
},
{ },
};
Expand All @@ -2648,6 +2868,8 @@ 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);
Expand Down
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