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[128.2.16.9]) by smtp.gmail.com with ESMTPSA id f13-20020a05620a408d00b006bb78d095c5sm12188520qko.79.2022.11.23.05.05.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Nov 2022 05:05:20 -0800 (PST) From: Gabriel Somlo To: linux-kernel@vger.kernel.org Cc: linux-serial@vger.kernel.org, gregkh@linuxfoundation.org, jirislaby@kernel.org, kgugala@antmicro.com, mholenko@antmicro.com, joel@jms.id.au, david.abdurachmanov@gmail.com, florent@enjoy-digital.fr, geert@linux-m68k.org, ilpo.jarvinen@linux.intel.com Subject: [PATCH v6 12/14] serial: liteuart: add IRQ support for the RX path Date: Wed, 23 Nov 2022 08:04:58 -0500 Message-Id: <20221123130500.1030189-13-gsomlo@gmail.com> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221123130500.1030189-1-gsomlo@gmail.com> References: <20221123130500.1030189-1-gsomlo@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org Add support for IRQ-driven RX. Support for the TX path will be added in a separate commit. Signed-off-by: Gabriel Somlo Reviewed-by: Ilpo Järvinen --- Changes from v5: - s/dev_err/dev_warn/ when falling back to polling in `liteuart_startup()` - use `spin_[lock_irqsave|unlock_irqrestore]()` in the interrupt handler, since the same code may also be called in "serving_softirq" context when using a poll timer instead of hardware interrupts > Changes from v4: > - using dev_err() instead of a combo of pr_err() and pr_fmt() > - dropped "get irq" comment in probe() > > 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 | 81 ++++++++++++++++++++++++++++++++--- 1 file changed, 74 insertions(+), 7 deletions(-) diff --git a/drivers/tty/serial/liteuart.c b/drivers/tty/serial/liteuart.c index 0b9d96e5efcf..8685c97d391e 100644 --- a/drivers/tty/serial/liteuart.c +++ b/drivers/tty/serial/liteuart.c @@ -7,6 +7,7 @@ #include #include +#include #include #include #include @@ -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 +144,32 @@ 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; + unsigned long flags; + u8 isr; + + /* + * if polling, the context would be "in_serving_softirq", so use + * irq[save|restore] spin_lock variants to cover all possibilities + */ + spin_lock_irqsave(&port->lock, flags); + isr = litex_read8(port->membase + OFF_EV_PENDING) & uart->irq_reg; + if (isr & EV_RX) + liteuart_rx_chars(port); + spin_unlock_irqrestore(&port->lock, flags); + + 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 +195,46 @@ 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) { + dev_warn(port->dev, + "line %d irq %d failed: switch to polling\n", + port->line, port->irq); + 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 +323,12 @@ static int liteuart_probe(struct platform_device *pdev) goto err_erase_id; } + 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;