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

Krzysztof Kozlowski
2021-02-15T19:14:17Z

On Mon, Feb 15, 2021 at 09:17:10PM +0900, Hector Martin wrote:
> 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);

You are now configuring the PIO mode after unmasking interrupt. I don't
think it's a good idea to change the order... and if it were, it
would deserve a separate patch.

> +
> 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: {

Usually you put TYPE_APPLE at the end of switch, so please keep it
consistent. Can be first or last - just everywhere the same, unless you
have a fall-through on purpose.

> + 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);

We should start checking the return values of clk operations. I know
that existing code does it only in few places, so basically you are not
making it worse...

> +
> + 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
> +
> +

Only one line break.

Best regards,
Krzysztof