Re: [PATCH 14/15] tty: serial: Add Nuvoton ma35d1 serial driver support

From: Jiri Slaby
Date: Wed Mar 15 2023 - 06:14:19 EST

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In reply to: kernel test robot: "Re: [PATCH 14/15] tty: serial: Add Nuvoton ma35d1 serial driver support"
Next in thread: Jacky Huang: "[PATCH 15/15] MAINTAINERS: Add entry for NUVOTON MA35"
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On 15. 03. 23, 8:29, Jacky Huang wrote:

--- /dev/null
+++ b/drivers/tty/serial/ma35d1_serial.c
@@ -0,0 +1,842 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * MA35D1 serial driver
+ * Copyright (C) 2023 Nuvoton Technology Corp.
+ */
+
+#include <linux/module.h>
+#include <linux/moduleparam.h>

What parameters does this module have?

+#include <linux/ioport.h>
+#include <linux/init.h>
+#include <linux/console.h>
+#include <linux/sysrq.h>
+#include <linux/delay.h>

What do you use from delay.h?

+#include <linux/platform_device.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+#include <linux/clk.h>
+#include <linux/serial_reg.h>
+#include <linux/serial_core.h>
+#include <linux/serial.h>
+#include <linux/nmi.h>

nmi.h?

Please clean up all of the includes.

+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/of_address.h>
+#include <linux/of_platform.h>
+#include <linux/io.h>
+#include <asm/irq.h>
+#include <asm/serial.h>
+#include "ma35d1_serial.h"
+
+#define UART_NR 17
+
+static struct uart_driver ma35d1serial_reg;
+struct clk *clk;
+
+struct uart_ma35d1_port {
+ struct uart_port port;
+ u16 capabilities; /* port capabilities */
+ u8 ier;
+ u8 lcr;
+ u8 mcr;
+ u8 mcr_mask; /* mask of user bits */
+ u8 mcr_force; /* mask of forced bits */

Where are all those used?

+ struct serial_rs485 rs485; /* rs485 settings */
+ u32 baud_rate;

And this one.

+ int rx_count;
+ u32 console_baud_rate;
+ u32 console_line;
+ u32 console_int;
+};
+
+static struct device_node *ma35d1serial_uart_nodes[UART_NR];
+static struct uart_ma35d1_port ma35d1serial_ports[UART_NR] = { 0 };

+static void __stop_tx(struct uart_ma35d1_port *p);

What for?

+static void transmit_chars(struct uart_ma35d1_port *up);
+
+static struct uart_ma35d1_port *to_ma35d1_uart_port(struct uart_port *uart)
+{
+ return container_of(uart, struct uart_ma35d1_port, port);
+}
+
+static u32 serial_in(struct uart_ma35d1_port *p, int offset)

Q: int? A: No.

+{
+ return __raw_readl(p->port.membase + offset);
+}
+
+static void serial_out(struct uart_ma35d1_port *p, int offset, int value)

No ints here, please.

+{
+ __raw_writel(value, p->port.membase + offset);
+}
+
+static void __stop_tx(struct uart_ma35d1_port *p)
+{
+ u32 ier;
+
+ ier = serial_in(p, UART_REG_IER);
+ if (ier & THRE_IEN)
+ serial_out(p, UART_REG_IER, ier & ~THRE_IEN);
+}
+
+static void ma35d1serial_stop_tx(struct uart_port *port)
+{
+ struct uart_ma35d1_port *up = (struct uart_ma35d1_port *)port;

Despite you have to_ma35d1_uart_port(), you do this?

+
+ __stop_tx(up);
+}
+
+static void ma35d1serial_start_tx(struct uart_port *port)
+{
+ struct uart_ma35d1_port *up = (struct uart_ma35d1_port *)port;
+ u32 ier;
+ struct circ_buf *xmit = &up->port.state->xmit;
+
+ ier = serial_in(up, UART_REG_IER);
+ serial_out(up, UART_REG_IER, ier & ~THRE_IEN);
+ if (uart_circ_chars_pending(xmit) <
+ (16 - ((serial_in(up, UART_REG_FSR) >> 16) & 0x3F)))

You look like you need a helper for this computation (hint: GENMASK()). What do those magic constants mean?

+ transmit_chars(up);
+ serial_out(up, UART_REG_IER, ier | THRE_IEN);
+}
+
+static void ma35d1serial_stop_rx(struct uart_port *port)
+{
+ struct uart_ma35d1_port *up = (struct uart_ma35d1_port *)port;

Bah. Nah.

+
+ serial_out(up, UART_REG_IER, serial_in(up, UART_REG_IER) & ~RDA_IEN);
+}
+
+static void
+receive_chars(struct uart_ma35d1_port *up)
+{
+ u8 ch;
+ u32 fsr;
+ u32 isr;
+ u32 dcnt;
+ char flag;

flag is u8 too. And a reverse xmas tree, please. Actually, you can put all those u32 to a single line.

+
+ isr = serial_in(up, UART_REG_ISR);
+ fsr = serial_in(up, UART_REG_FSR);
+
+ while (!(fsr & RX_EMPTY)) {
+ flag = TTY_NORMAL;
+ up->port.icount.rx++;
+
+ if (unlikely(fsr & (BIF | FEF | PEF | RX_OVER_IF))) {
+ if (fsr & BIF) {
+ serial_out(up, UART_REG_FSR, BIF);
+ up->port.icount.brk++;
+ if (uart_handle_break(&up->port))
+ continue;
+ }
+ if (fsr & FEF) {
+ serial_out(up, UART_REG_FSR, FEF);
+ up->port.icount.frame++;
+ }
+ if (fsr & PEF) {
+ serial_out(up, UART_REG_FSR, PEF);
+ up->port.icount.parity++;
+ }
+ if (fsr & RX_OVER_IF) {
+ serial_out(up, UART_REG_FSR, RX_OVER_IF);
+ up->port.icount.overrun++;
+ }
+ if (fsr & BIF)
+ flag = TTY_BREAK;
+ if (fsr & PEF)
+ flag = TTY_PARITY;
+ if (fsr & FEF)
+ flag = TTY_FRAME;
+ }
+ ch = (u8)serial_in(up, UART_REG_RBR);
+ if (uart_handle_sysrq_char(&up->port, ch))
+ continue;
+
+ uart_insert_char(&up->port, fsr, RX_OVER_IF, ch, flag);

No lock needed?

+ up->rx_count++;
+ dcnt = (serial_in(up, UART_REG_FSR) >> 8) & 0x3f;

More magic constants. No.

+ if (up->rx_count > 1023) {
+ spin_lock(&up->port.lock);
+ tty_flip_buffer_push(&up->port.state->port);
+ spin_unlock(&up->port.lock);
+ up->rx_count = 0;
+ if ((isr & RXTO_IF) && (dcnt == 0))
+ goto tout_end;
+ }
+ if (isr & RDA_IF) {
+ if (dcnt == 1)
+ return;
+ }
+ fsr = serial_in(up, UART_REG_FSR);
+ }
+ spin_lock(&up->port.lock);
+ tty_flip_buffer_push(&up->port.state->port);
+ spin_unlock(&up->port.lock);
+tout_end:
+ up->rx_count = 0;
+}
+
+static void transmit_chars(struct uart_ma35d1_port *up)

Why this cannot use uart_port_tx()?

+{
+ struct circ_buf *xmit = &up->port.state->xmit;
+ int count = 16 - ((serial_in(up, UART_REG_FSR) >> 16) & 0xF);
+
+ if (serial_in(up, UART_REG_FSR) & TX_FULL)
+ count = 0;
+ if (up->port.x_char) {
+ serial_out(up, UART_REG_THR, up->port.x_char);
+ up->port.icount.tx++;
+ up->port.x_char = 0;
+ return;
+ }
+ if (uart_tx_stopped(&up->port)) {
+ ma35d1serial_stop_tx(&up->port);
+ return;
+ }
+ if (uart_circ_empty(xmit)) {
+ __stop_tx(up);
+ return;
+ }
+ while (count > 0) {
+ serial_out(up, UART_REG_THR, xmit->buf[xmit->tail]);
+ xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
+ up->port.icount.tx++;
+ count--;
+ if (uart_circ_empty(xmit))
+ break;
+ }
+ if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+ uart_write_wakeup(&up->port);
+ if (uart_circ_empty(xmit))
+ __stop_tx(up);
+}
+
+static irqreturn_t ma35d1serial_interrupt(int irq, void *dev_id)
+{
+ struct uart_ma35d1_port *up = (struct uart_ma35d1_port *)dev_id;
+ u32 isr, fsr;
+
+ isr = serial_in(up, UART_REG_ISR);
+ fsr = serial_in(up, UART_REG_FSR);
+ if (isr & (RDA_IF | RXTO_IF))
+ receive_chars(up);
+ if (isr & THRE_INT)
+ transmit_chars(up);
+ if (fsr & (BIF | FEF | PEF | RX_OVER_IF | TX_OVER_IF))
+ serial_out(up, UART_REG_FSR,
+ (BIF | FEF | PEF | RX_OVER_IF | TX_OVER_IF));
+
+ return IRQ_HANDLED;

You give no way for OS to disable the irq when the HW goes crazy. I.e. you should return IRQ_HANDLED only when you really handled the irq.

+}

...

+static u32 ma35d1serial_get_mctrl(struct uart_port *port)
+{
+ struct uart_ma35d1_port *up = (struct uart_ma35d1_port *)port;
+ u32 status;
+ u32 ret = 0;
+
+ status = serial_in(up, UART_REG_MSR);
+ if (!(status & 0x10))

0x10 is magic.

+ ret |= TIOCM_CTS;
+ return ret;
+}
+
+static void ma35d1serial_set_mctrl(struct uart_port *port, u32 mctrl)
+{
+ struct uart_ma35d1_port *up = (struct uart_ma35d1_port *)port;
+ u32 mcr = 0;
+ u32 ier = 0;
+
+ if (mctrl & TIOCM_RTS) {
+ /* set RTS high level trigger */
+ mcr = serial_in(up, UART_REG_MCR);
+ mcr |= 0x200;
+ mcr &= ~(0x2);
+ }
+ if (up->mcr & UART_MCR_AFE) {
+ /* set RTS high level trigger */
+ mcr = serial_in(up, UART_REG_MCR);
+ mcr |= 0x200;
+ mcr &= ~(0x2);

This is repeated. Parentheses are superfluous. And again, 0x200, 0x2 are magic.

+
+ /* enable CTS/RTS auto-flow control */
+ serial_out(up, UART_REG_IER,
+ (serial_in(up, UART_REG_IER) | (0x3000)));
+
+ /* Set hardware flow control */
+ up->port.flags |= UPF_HARD_FLOW;
+ } else {
+ /* disable CTS/RTS auto-flow control */
+ ier = serial_in(up, UART_REG_IER);
+ ier &= ~(0x3000);

Detto.

+ serial_out(up, UART_REG_IER, ier);
+
+ /* un-set hardware flow control */
+ up->port.flags &= ~UPF_HARD_FLOW;
+ }
+
+ /* set CTS high level trigger */
+ serial_out(up, UART_REG_MSR, (serial_in(up, UART_REG_MSR) | (0x100)));
+ serial_out(up, UART_REG_MCR, mcr);
+}

...

+static int ma35d1serial_startup(struct uart_port *port)
+{
+ struct uart_ma35d1_port *up = (struct uart_ma35d1_port *)port;
+ struct tty_struct *tty = port->state->port.tty;
+ int retval;
+
+ /* Reset FIFO */
+ serial_out(up, UART_REG_FCR, TFR | RFR /* | RX_DIS */);

So why not RX_DIS?

+
+ /* Clear pending interrupts */
+ serial_out(up, UART_REG_ISR, 0xFFFFFFFF);
+
+ retval = request_irq(port->irq, ma35d1serial_interrupt, 0,
+ tty ? tty->name : "ma35d1_serial", port);
+ if (retval) {
+ dev_err(up->port.dev, "request irq failed.\n");
+ return retval;
+ }
+
+ /* Now, initialize the UART */
+ /* FIFO trigger level 4 byte */
+ /* RTS trigger level 8 bytes */
+ serial_out(up, UART_REG_FCR,
+ serial_in(up, UART_REG_FCR) | 0x10 | 0x20000);
+ serial_out(up, UART_REG_LCR, 0x7); /* 8 bit */
+ serial_out(up, UART_REG_TOR, 0x40);

You know what.

+ serial_out(up, UART_REG_IER,
+ RTO_IEN | RDA_IEN | TIME_OUT_EN | BUFERR_IEN);
+ return 0;
+}
+
+static void ma35d1serial_shutdown(struct uart_port *port)
+{
+ struct uart_ma35d1_port *up = (struct uart_ma35d1_port *)port;
+
+ free_irq(port->irq, port);
+
+ /* Disable interrupts from this port */
+ serial_out(up, UART_REG_IER, 0);

The two lines are switched, IMO. First disable HW, then let the ISR finish and free it.

+}
+
+static u32 ma35d1serial_get_divisor(struct uart_port *port, u32 baud)
+{
+ u32 quot;
+
+ quot = (port->uartclk / baud) - 2;
+ return quot;

quot variable is completely superfluous.

+}
+
+static void ma35d1serial_set_termios(struct uart_port *port,
+ struct ktermios *termios,
+ const struct ktermios *old)
+{
+ struct uart_ma35d1_port *up = (struct uart_ma35d1_port *)port;
+ u32 lcr = 0;
+ unsigned long flags;
+ u32 baud, quot;
+
+ switch (termios->c_cflag & CSIZE) {
+ case CS5:
+ lcr = 0;
+ break;
+ case CS6:
+ lcr |= 1;
+ break;
+ case CS7:
+ lcr |= 2;
+ break;
+ case CS8:
+ default:
+ lcr |= 3;
+ break;
+ }

IOW:
lcr = UART_LCR_WLEN(tty_get_char_size(termios->c_cflag));

+
+ if (termios->c_cflag & CSTOPB)
+ lcr |= NSB;
+ if (termios->c_cflag & PARENB)
+ lcr |= PBE;
+ if (!(termios->c_cflag & PARODD))
+ lcr |= EPE;
+ if (termios->c_cflag & CMSPAR)
+ lcr |= SPE;
+
+ baud = uart_get_baud_rate(port, termios, old, port->uartclk / 0xffff,
+ port->uartclk / 11);
+
+ quot = ma35d1serial_get_divisor(port, baud);
+
+ /*
+ * Ok, we're now changing the port state. Do it with
+ * interrupts disabled.
+ */
+ spin_lock_irqsave(&up->port.lock, flags);
+
+ up->port.read_status_mask = RX_OVER_IF;
+ if (termios->c_iflag & INPCK)
+ up->port.read_status_mask |= FEF | PEF;
+ if (termios->c_iflag & (BRKINT | PARMRK))
+ up->port.read_status_mask |= BIF;
+
+ /*
+ * Characteres to ignore
+ */
+ up->port.ignore_status_mask = 0;
+ if (termios->c_iflag & IGNPAR)
+ up->port.ignore_status_mask |= FEF | PEF;
+ if (termios->c_iflag & IGNBRK) {
+ up->port.ignore_status_mask |= BIF;
+ /*
+ * If we're ignoring parity and break indicators,
+ * ignore overruns too (for real raw support).
+ */
+ if (termios->c_iflag & IGNPAR)
+ up->port.ignore_status_mask |= RX_OVER_IF;
+ }
+ if (termios->c_cflag & CRTSCTS)
+ up->mcr |= UART_MCR_AFE;
+ else
+ up->mcr &= ~UART_MCR_AFE;
+
+ ma35d1serial_set_mctrl(&up->port, up->port.mctrl);
+ serial_out(up, UART_REG_BAUD, quot | 0x30000000);
+ serial_out(up, UART_REG_LCR, lcr);
+ spin_unlock_irqrestore(&up->port.lock, flags);
+}

...

+static void ma35d1serial_config_port(struct uart_port *port, int flags)
+{
+ int ret;
+
+ /*
+ * Find the region that we can probe for. This in turn
+ * tells us whether we can probe for the type of port.
+ */
+ ret = ma35d1serial_request_port(port);
+ if (ret < 0)
+ return;

ma35d1serial_request_port() does nothing. You can remove it altogether.

+ port->type = PORT_MA35D1;
+}

+static int ma35d1serial_ioctl(struct uart_port *port, u32 cmd, unsigned long arg)
+{
+ switch (cmd) {
+ default:
+ return -ENOIOCTLCMD;
+ }
+ return 0;
+}

Drop that completely.

+static void
+ma35d1serial_console_init_port(void)
+{
+ int i = 0;
+ struct device_node *np;
+
+ for_each_matching_node(np, ma35d1_serial_of_match) {
+ if (ma35d1serial_uart_nodes[i] == NULL) {
+ ma35d1serial_uart_nodes[i] = np;
+ i++;

Unless the dt is broken, this is OK. But I would add a sanity check to i.

+ }
+ }
+}

...

+/*
+ * Register a set of serial devices attached to a platform device.
+ * The list is terminated with a zero flags entry, which means we expect
+ * all entries to have at least UPF_BOOT_AUTOCONF set.
+ */
+static int ma35d1serial_probe(struct platform_device *pdev)
+{
+ struct resource *res_mem;
+ struct uart_ma35d1_port *up;
+ int ret;
+ struct clk *clk;
+ int err;
+
+ if (pdev->dev.of_node) {
+ ret = of_alias_get_id(pdev->dev.of_node, "serial");
+ if (ret < 0) {
+ dev_err(&pdev->dev,
+ "failed to get alias/pdev id, errno %d\n",
+ ret);
+ return ret;
+ }
+ }
+ up = &ma35d1serial_ports[ret];
+ up->port.line = ret;
+ res_mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ if (!res_mem)
+ return -ENODEV;
+
+ up->port.iobase = res_mem->start;
+ up->port.membase = ioremap(up->port.iobase, 0x10000);
+ up->port.ops = &ma35d1serial_ops;
+
+ spin_lock_init(&up->port.lock);
+
+ clk = of_clk_get(pdev->dev.of_node, 0);
+ if (IS_ERR(clk)) {
+ err = PTR_ERR(clk);
+ dev_err(&pdev->dev, "failed to get core clk: %d\n", err);
+ return -ENOENT;
+ }
+ err = clk_prepare_enable(clk);
+ if (err)
+ return -ENOENT;
+
+ if (up->port.line != 0)
+ up->port.uartclk = clk_get_rate(clk);
+ up->port.irq = platform_get_irq(pdev, 0);
+ up->port.dev = &pdev->dev;
+ up->port.flags = UPF_BOOT_AUTOCONF;
+ up->port.rs485_config = ma35d1serial_config_rs485;
+ ret = uart_add_one_port(&ma35d1serial_reg, &up->port);

What if this fails?

+ platform_set_drvdata(pdev, up);
+ return 0;
+}
+
+/*
+ * Remove serial ports registered against a platform device.
+ */
+static int ma35d1serial_remove(struct platform_device *dev)
+{
+ int i;
+ struct uart_port *port = platform_get_drvdata(dev);
+
+ free_irq(port->irq, port);

Hmm, this doesn't look right. You did that already, or?

+ for (i = 0; i < UART_NR; i++) {
+ struct uart_ma35d1_port *up = &ma35d1serial_ports[i];
+
+ if (up->port.dev == &dev->dev)

You did platform_set_drvdata(), so why all this?

+ uart_remove_one_port(&ma35d1serial_reg, &up->port);
+ }
+ return 0;
+}

regards,
--
js
suse labs

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