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

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Dear Jiri,


Thanks for your review.

I will create #define constant to replace every occurrence of magics or
hard coding number.

For every occurrence of "struct uart_ma35d1_port *up = (struct uart_ma35d1_port *)port; ",
it will be replaced with to_ma35d1_uart_port() .


On 2023/3/15 下午 06:13, Jiri Slaby wrote:
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.


moduleparam.h, delay.h, and nmi.h are not used.

I will test and remove all unused #include.

+#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?


I will remove the unused structure members in the next version.

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

And this one.


It's not used. I will remove it.

+    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?

This function is used to disable TX FIFO empty interrupt.

naming issue?


+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.

will modify "int offset" to "u32 offset"


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

No ints here, please.

will modify offset and value data type to u32



+{
+    __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?


You're right. I will use to_ma35d1_uart_port() to replace it.


+
+    __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?


I will add #define macro for the bit mask..

+        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.


OK, I will fix it.

+
+    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?


I will wrap it with spin_lock and spin_unlock.

+        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()?

OK, I will rename it as 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.

You're right. I will fix 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.

remove quot
and
return (port->uartclk / baud) - 2;


+}
+
+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));

All registers in this uart controller are 32-bits.
lcr will finally be written to the register UART_REG_LCR.of
which bit[1:0] represents for UART word length.
00 - 5 bits
01 - 6 bits
10 - 7 bits
11 - 8bits

Instead, I will add
#define WLS_5    0x0
#define WLS_6    0x1
#define WLS_7    0x2
#define WLS_8    0x3

and replace lcr |= 1 with
lcr |= WLS_6;

+
+    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.


OK, I will remove it.

+    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.


OK.

+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.


I will add
if (i == UART_NR)
    break;


+        }
+    }
+}
...
+/*
+ * 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?


I will add return value check.

+    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?


static int ma35d1serial_remove(struct platform_device *dev)
{
    struct uart_port *port = platform_get_drvdata(dev);

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


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



Best Regards,

Jacky Huang





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