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Message-ID: <553a8dbd-08b9-488a-a024-f89697908b41@kernel.org>
Date: Wed, 20 Sep 2023 09:22:35 +0200
From: Jiri Slaby <jirislaby@...nel.org>
To: Max Filippov <jcmvbkbc@...il.com>, linux-kernel@...r.kernel.org,
linux-serial@...r.kernel.org, devicetree@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Conor Dooley <conor+dt@...nel.org>,
Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Subject: Re: [PATCH v2 3/5] drivers/tty/serial: add driver for the ESP32 UART
On 20. 09. 23, 4:26, Max Filippov wrote:
> Add driver for the UART controllers of the Espressif ESP32 and ESP32S3
> SoCs. Hardware specification is available at the following URLs:
...
> +static void esp32_uart_rxint(struct uart_port *port)
> +{
> + struct tty_port *tty_port = &port->state->port;
> + u32 rx_fifo_cnt = esp32_uart_rx_fifo_cnt(port);
> + unsigned long flags;
> + u32 i;
> +
> + if (!rx_fifo_cnt)
> + return;
> +
> + spin_lock_irqsave(&port->lock, flags);
> +
> + for (i = 0; i < rx_fifo_cnt; ++i) {
> + u32 rx = esp32_uart_read(port, UART_FIFO_REG);
> + u32 brk = 0;
> +
> + ++port->icount.rx;
Should yuou increment this only in case of insert_flip_char()?
> + if (!rx) {
> + brk = esp32_uart_read(port, UART_INT_ST_REG) &
> + UART_BRK_DET_INT;
> + }
> + if (brk) {
> + esp32_uart_write(port, UART_INT_CLR_REG, brk);
> + ++port->icount.brk;
> + uart_handle_break(port);
> + } else {
> + if (uart_handle_sysrq_char(port, (unsigned char)rx))
> + continue;
> + tty_insert_flip_char(tty_port, rx, TTY_NORMAL);
> + }
This is heavy. Is it equivalent to:
if (!rx && esp32_uart_read(port, UART_INT_ST_REG) &
UART_BRK_DET_INT) {
esp32_uart_write(port, UART_INT_CLR_REG, brk);
++port->icount.brk;
uart_handle_break(port);
continue;
}
if (uart_handle_sysrq_char(port, (unsigned char)rx))
continue;
tty_insert_flip_char(tty_port, rx, TTY_NORMAL);
?
> + }
> + spin_unlock_irqrestore(&port->lock, flags);
> +
> + tty_flip_buffer_push(tty_port);
> +}
...
> +static void esp32_uart_put_char_sync(struct uart_port *port, u8 c)
> +{
> + unsigned long timeout;
> +
> + timeout = jiffies + msecs_to_jiffies(1000);
I.e. plus HZ?
> + while (esp32_uart_tx_fifo_cnt(port) >= ESP32_UART_TX_FIFO_SIZE) {
> + if (time_after(jiffies, timeout)) {
> + dev_warn(port->dev, "timeout waiting for TX FIFO\n");
> + return;
> + }
> + cpu_relax();
> + }
> + esp32_uart_put_char(port, c);
> +}
> +
> +static void esp32_uart_transmit_buffer(struct uart_port *port)
> +{
> + u32 tx_fifo_used = esp32_uart_tx_fifo_cnt(port);
> +
> + if (tx_fifo_used < ESP32_UART_TX_FIFO_SIZE) {
Invert the condition and return here?
> + unsigned int pending;
> + u8 ch;
> +
> + pending = uart_port_tx_limited(port, ch,
> + ESP32_UART_TX_FIFO_SIZE - tx_fifo_used,
> + true, esp32_uart_put_char(port, ch),
> + ({}));
> + if (pending) {
> + u32 int_ena;
> +
> + int_ena = esp32_uart_read(port, UART_INT_ENA_REG);
> + int_ena |= UART_TXFIFO_EMPTY_INT;
> + esp32_uart_write(port, UART_INT_ENA_REG, int_ena);
> + }
> + }
> +}
> +static irqreturn_t esp32_uart_int(int irq, void *dev_id)
> +{
> + struct uart_port *port = dev_id;
> + u32 status;
> +
> + status = esp32_uart_read(port, UART_INT_ST_REG);
> +
> + if (status & (UART_RXFIFO_FULL_INT | UART_BRK_DET_INT))
> + esp32_uart_rxint(port);
> + if (status & UART_TXFIFO_EMPTY_INT)
> + esp32_uart_txint(port);
> +
> + esp32_uart_write(port, UART_INT_CLR_REG, status);
\n here please.
> + return IRQ_RETVAL(status);
> +}
> +static int esp32_uart_startup(struct uart_port *port)
> +{
> + int ret = 0;
> + unsigned long flags;
> + struct esp32_port *sport = container_of(port, struct esp32_port, port);
> +
> + ret = clk_prepare_enable(sport->clk);
> + if (ret)
> + return ret;
> +
> + ret = devm_request_irq(port->dev, port->irq, esp32_uart_int, 0,
> + DRIVER_NAME, port);
> + if (ret) {
> + clk_disable_unprepare(sport->clk);
> + return ret;
> + }
> +
> + spin_lock_irqsave(&port->lock, flags);
> + esp32_uart_write(port, UART_CONF1_REG,
> + (1 << UART_RXFIFO_FULL_THRHD_SHIFT) |
BIT() ?
> + (1 << port_variant(port)->txfifo_empty_thrhd_shift));
And here?
> + esp32_uart_write(port, UART_INT_CLR_REG, UART_RXFIFO_FULL_INT | UART_BRK_DET_INT);
> + esp32_uart_write(port, UART_INT_ENA_REG, UART_RXFIFO_FULL_INT | UART_BRK_DET_INT);
> + spin_unlock_irqrestore(&port->lock, flags);
> +
> + pr_debug("%s, conf1 = %08x, int_st = %08x, status = %08x\n",
> + __func__,
> + esp32_uart_read(port, UART_CONF1_REG),
> + esp32_uart_read(port, UART_INT_ST_REG),
> + esp32_uart_read(port, UART_STATUS_REG));
\n here. Is this debug printout somehow useful?
> + return ret;
> +}
> +
> +static void esp32_uart_shutdown(struct uart_port *port)
> +{
> + struct esp32_port *sport = container_of(port, struct esp32_port, port);
> +
> + esp32_uart_write(port, UART_INT_ENA_REG, 0);
> + devm_free_irq(port->dev, port->irq, port);
I wonder why to use devm_ after all?
> + clk_disable_unprepare(sport->clk);
> +}
> +
> +static bool esp32_uart_set_baud(struct uart_port *port, u32 baud)
> +{
> + u32 div = port->uartclk / baud;
> + u32 frag = (port->uartclk * 16) / baud - div * 16;
> +
> + if (div <= port_variant(port)->clkdiv_mask) {
> + esp32_uart_write(port, UART_CLKDIV_REG,
> + div | FIELD_PREP(UART_CLKDIV_FRAG, frag));
> + return true;
> + }
\n
> + return false;
> +}
...
> +static int __init esp32s3_uart_early_console_setup(struct earlycon_device *device,
> + const char *options)
> +{
> + device->port.private_data = (void *)&esp32s3_variant;
No need to cast, right?
\n
> + return esp32xx_uart_early_console_setup(device, options);
> +}
...
> +static int esp32_uart_probe(struct platform_device *pdev)
> +{
> + struct device_node *np = pdev->dev.of_node;
> + static const struct of_device_id *match;
> + struct uart_port *port;
> + struct esp32_port *sport;
> + struct resource *res;
> + int ret;
> +
> + match = of_match_device(esp32_uart_dt_ids, &pdev->dev);
> + if (!match)
> + return -ENODEV;
> +
> + sport = devm_kzalloc(&pdev->dev, sizeof(*sport), GFP_KERNEL);
> + if (!sport)
> + return -ENOMEM;
> +
> + port = &sport->port;
> +
> + ret = of_alias_get_id(np, "serial");
> + if (ret < 0) {
> + dev_err(&pdev->dev, "failed to get alias id, errno %d\n", ret);
> + return ret;
> + }
> + if (ret >= UART_NR) {
> + dev_err(&pdev->dev, "driver limited to %d serial ports\n", UART_NR);
> + return -ENOMEM;
> + }
> +
> + port->line = ret;
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + if (!res)
> + return -ENODEV;
> +
> + port->mapbase = res->start;
> + port->membase = devm_ioremap_resource(&pdev->dev, res);
> + if (IS_ERR(port->membase))
> + return PTR_ERR(port->membase);
> +
> + sport->clk = devm_clk_get(&pdev->dev, NULL);
> + if (IS_ERR(sport->clk))
> + return PTR_ERR(sport->clk);
> +
> + port->uartclk = clk_get_rate(sport->clk);
> + port->dev = &pdev->dev;
> + port->type = PORT_ESP32UART;
> + port->iotype = UPIO_MEM;
> + port->irq = platform_get_irq(pdev, 0);
> + port->ops = &esp32_uart_pops;
> + port->flags = UPF_BOOT_AUTOCONF;
> + port->has_sysrq = 1;
> + port->fifosize = ESP32_UART_TX_FIFO_SIZE;
> + port->private_data = (void *)match->data;
No need to cast.
> +
> + esp32_uart_ports[port->line] = sport;
> +
> + platform_set_drvdata(pdev, port);
> +
> + return uart_add_one_port(&esp32_uart_reg, port);
> +}
regards,
--
js
suse labs
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