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Message-ID: <Y3eWJNbcGJOMl7K1@errol.ini.cmu.edu>
Date: Fri, 18 Nov 2022 09:26:44 -0500
From: "Gabriel L. Somlo" <gsomlo@...il.com>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.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 Fri, Nov 18, 2022 at 03:58:47PM +0200, Ilpo Järvinen wrote:
> 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.
Makes sense, good thing `struct uart_port` has a `dev` field :)
I've made the change, and lined it up for the upcoming v5 of the
series.
> > + 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.
Removed in v5.
> Other than that,
>
> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Thanks much, I'll send out v5 a bit later today.
--Gabriel
> --
> 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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