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Date: Fri, 18 Nov 2022 15:58:47 +0200 (EET)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Gabriel Somlo <gsomlo@...il.com>
cc: LKML <linux-kernel@...r.kernel.org>,
linux-serial <linux-serial@...r.kernel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jiri Slaby <jirislaby@...nel.org>, kgugala@...micro.com,
mholenko@...micro.com, joel@....id.au,
david.abdurachmanov@...il.com, florent@...oy-digital.fr,
geert@...ux-m68k.org
Subject: Re: [PATCH v4 12/14] serial: liteuart: add IRQ support for the RX
path
On Wed, 16 Nov 2022, Gabriel Somlo wrote:
> Add support for IRQ-driven RX. Support for the TX path will be added
> in a separate commit.
>
> Signed-off-by: Gabriel Somlo <gsomlo@...il.com>
> ---
>
> Changes from v3:
> - add shadow irq register to support polling mode and avoid reading
> hardware mmio irq register to learn which irq flags are enabled
> - this also simplifies both liteuart_interrupt() and liteuart_startup()
>
> drivers/tty/serial/liteuart.c | 76 +++++++++++++++++++++++++++++++----
> 1 file changed, 69 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/tty/serial/liteuart.c b/drivers/tty/serial/liteuart.c
> index 8a6e176be08e..fad778578986 100644
> --- a/drivers/tty/serial/liteuart.c
> +++ b/drivers/tty/serial/liteuart.c
> @@ -7,6 +7,7 @@
>
> #include <linux/bits.h>
> #include <linux/console.h>
> +#include <linux/interrupt.h>
> #include <linux/litex.h>
> #include <linux/module.h>
> #include <linux/of.h>
> @@ -46,6 +47,7 @@ struct liteuart_port {
> struct uart_port port;
> struct timer_list timer;
> u32 id;
> + u8 irq_reg;
> };
>
> #define to_liteuart_port(port) container_of(port, struct liteuart_port, port)
> @@ -76,6 +78,19 @@ static void liteuart_putchar(struct uart_port *port, unsigned char ch)
> litex_write8(port->membase + OFF_RXTX, ch);
> }
>
> +static void liteuart_update_irq_reg(struct uart_port *port, bool set, u8 mask)
> +{
> + struct liteuart_port *uart = to_liteuart_port(port);
> +
> + if (set)
> + uart->irq_reg |= mask;
> + else
> + uart->irq_reg &= ~mask;
> +
> + if (port->irq)
> + litex_write8(port->membase + OFF_EV_ENABLE, uart->irq_reg);
> +}
> +
> static void liteuart_stop_tx(struct uart_port *port)
> {
> }
> @@ -129,13 +144,27 @@ static void liteuart_rx_chars(struct uart_port *port)
> tty_flip_buffer_push(&port->state->port);
> }
>
> +static irqreturn_t liteuart_interrupt(int irq, void *data)
> +{
> + struct liteuart_port *uart = data;
> + struct uart_port *port = &uart->port;
> + u8 isr;
> +
> + spin_lock(&port->lock);
> + isr = litex_read8(port->membase + OFF_EV_PENDING) & uart->irq_reg;
> + if (isr & EV_RX)
> + liteuart_rx_chars(port);
> + spin_unlock(&port->lock);
> +
> + return IRQ_RETVAL(isr);
> +}
> +
> static void liteuart_timer(struct timer_list *t)
> {
> struct liteuart_port *uart = from_timer(uart, t, timer);
> struct uart_port *port = &uart->port;
>
> - liteuart_rx_chars(port);
> -
> + liteuart_interrupt(0, port);
> mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
> }
>
> @@ -161,19 +190,45 @@ static unsigned int liteuart_get_mctrl(struct uart_port *port)
> static int liteuart_startup(struct uart_port *port)
> {
> struct liteuart_port *uart = to_liteuart_port(port);
> + unsigned long flags;
> + int ret;
>
> - /* disable events */
> - litex_write8(port->membase + OFF_EV_ENABLE, 0);
> + if (port->irq) {
> + ret = request_irq(port->irq, liteuart_interrupt, 0,
> + KBUILD_MODNAME, uart);
> + if (ret) {
> + pr_err(pr_fmt("line %d irq %d failed: using polling\n"),
> + port->line, port->irq);
dev_err() seems more appropriate here.
> + port->irq = 0;
> + }
> + }
>
> - /* prepare timer for polling */
> - timer_setup(&uart->timer, liteuart_timer, 0);
> - mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
> + spin_lock_irqsave(&port->lock, flags);
> + /* only enabling rx irqs during startup */
> + liteuart_update_irq_reg(port, true, EV_RX);
> + spin_unlock_irqrestore(&port->lock, flags);
> +
> + if (!port->irq) {
> + timer_setup(&uart->timer, liteuart_timer, 0);
> + mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
> + }
>
> return 0;
> }
>
> static void liteuart_shutdown(struct uart_port *port)
> {
> + struct liteuart_port *uart = to_liteuart_port(port);
> + unsigned long flags;
> +
> + spin_lock_irqsave(&port->lock, flags);
> + liteuart_update_irq_reg(port, false, EV_RX | EV_TX);
> + spin_unlock_irqrestore(&port->lock, flags);
> +
> + if (port->irq)
> + free_irq(port->irq, port);
> + else
> + del_timer_sync(&uart->timer);
> }
>
> static void liteuart_set_termios(struct uart_port *port, struct ktermios *new,
> @@ -262,6 +317,13 @@ static int liteuart_probe(struct platform_device *pdev)
> goto err_erase_id;
> }
>
> + /* get irq */
This comment is unnecessary.
Other than that,
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
--
i.
> + ret = platform_get_irq_optional(pdev, 0);
> + if (ret < 0 && ret != -ENXIO)
> + return ret;
> + if (ret > 0)
> + port->irq = ret;
> +
> /* values not from device tree */
> port->dev = &pdev->dev;
> port->iotype = UPIO_MEM;
>
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