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    Subjectpch_uart and pch_phub clock selection
    I'm working on a tunnel creek (atom e6xx + topcliff PCH) development platform
    that uses a 48MHz or 64MHz clock to drive the pch_uart. I've found that if I
    force the uart_clock to 48MHz (or 64MHz on the latest rev) I can get the kernel
    messages and getty on the serial port.

    I see that the the CM-iTC board is special-cased to set a 192MHz uart_clock.
    This is done in pch_uart.c code, but there is some register manipulation done in
    the pch_phub.c driver and I don't understand the connection. How are the two
    related?

    Is the pch_phub.c register manipulation required for proper related? It seems to
    work without touching those registers if I just force the clock.

    The device I'm working with is EFI, and the dmi_get_system_info(DMI_BOARD_NAME)
    returns "(null)", so I can't use the same test to identify this board. Is there
    another common mechanism I might be able to use?

    The following patch (by way of example, not meant for inclusion) gets things
    working for this particular board with this command line:

    console=ttyPCH1,115200 pch_uart.clock_param=48000000

    I believe the right thing to do here is to discover a way to identify the board
    and special case the clock as is done for the CM-iTC, but I would like to
    understand the purpose of the pch_phub register manipulation code. Does this
    make sense?

    Thanks,

    Darren


    >From f83fa6cb575844d8e37f136890fe32258eb88dd2 Mon Sep 17 00:00:00 2001
    Message-Id: <f83fa6cb575844d8e37f136890fe32258eb88dd2.1329439822.git.dvhart@linux.intel.com>
    From: Darren Hart <dvhart@linux.intel.com>
    Date: Wed, 15 Feb 2012 15:44:18 -0800
    Subject: [PATCH] pch_uart: Add clock parameter

    Allow for the specification of the clock as a module parameter. This is useful
    when a board uses a non-standard clock, or when different versions of a board
    use different clocks, and that board name or the version are not available to
    the kernel.

    Signed-off-by: Darren Hart <dvhart@linux.intel.com>
    ---
    drivers/tty/serial/pch_uart.c | 29 +++++++++++++++++------------
    1 files changed, 17 insertions(+), 12 deletions(-)

    diff --git a/drivers/tty/serial/pch_uart.c b/drivers/tty/serial/pch_uart.c
    index 17ae657..8f192b9 100644
    --- a/drivers/tty/serial/pch_uart.c
    +++ b/drivers/tty/serial/pch_uart.c
    @@ -203,7 +203,7 @@ enum {

    #define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)

    -#define DEFAULT_BAUD_RATE 1843200 /* 1.8432MHz */
    +#define DEFAULT_UART_CLOCK 1843200 /* 1.8432MHz */

    struct pch_uart_buffer {
    unsigned char *buf;
    @@ -218,7 +218,7 @@ struct eg20t_port {
    unsigned int iobase;
    struct pci_dev *pdev;
    int fifo_size;
    - int base_baud;
    + int uart_clock;
    int start_tx;
    int start_rx;
    int tx_empty;
    @@ -287,13 +287,14 @@ static struct pch_uart_driver_data drv_dat[] = {
    static struct eg20t_port *pch_uart_ports[PCH_UART_NR];
    #endif
    static unsigned int default_baud = 9600;
    +static unsigned int clock_param = 0;
    static const int trigger_level_256[4] = { 1, 64, 128, 224 };
    static const int trigger_level_64[4] = { 1, 16, 32, 56 };
    static const int trigger_level_16[4] = { 1, 4, 8, 14 };
    static const int trigger_level_1[4] = { 1, 1, 1, 1 };

    static void pch_uart_hal_request(struct pci_dev *pdev, int fifosize,
    - int base_baud)
    + int uart_clock)
    {
    struct eg20t_port *priv = pci_get_drvdata(pdev);

    @@ -332,7 +333,7 @@ static int pch_uart_hal_set_line(struct eg20t_port *priv, int baud,
    unsigned int dll, dlm, lcr;
    int div;

    - div = DIV_ROUND_CLOSEST(priv->base_baud / 16, baud);
    + div = DIV_ROUND_CLOSEST(priv->uart_clock / 16, baud);
    if (div < 0 || USHRT_MAX <= div) {
    dev_err(priv->port.dev, "Invalid Baud(div=0x%x)\n", div);
    return -EINVAL;
    @@ -1153,9 +1154,9 @@ static int pch_uart_startup(struct uart_port *port)
    priv->tx_empty = 1;

    if (port->uartclk)
    - priv->base_baud = port->uartclk;
    + priv->uart_clock = port->uartclk;
    else
    - port->uartclk = priv->base_baud;
    + port->uartclk = priv->uart_clock;

    pch_uart_hal_disable_interrupt(priv, PCH_UART_HAL_ALL_INT);
    ret = pch_uart_hal_set_line(priv, default_baud,
    @@ -1507,7 +1508,7 @@ static int __init pch_console_setup(struct console *co, char *options)
    return -ENODEV;

    /* setup uartclock */
    - port->uartclk = DEFAULT_BAUD_RATE;
    + port->uartclk = clock_param ? clock_param : DEFAULT_UART_CLOCK;

    if (options)
    uart_parse_options(options, &baud, &parity, &bits, &flow);
    @@ -1550,7 +1551,7 @@ static struct eg20t_port *pch_uart_init_port(struct pci_dev *pdev,
    unsigned int iobase;
    unsigned int mapbase;
    unsigned char *rxbuf;
    - int fifosize, base_baud;
    + int fifosize, uart_clock;
    int port_type;
    struct pch_uart_driver_data *board;
    const char *board_name;
    @@ -1566,12 +1567,15 @@ static struct eg20t_port *pch_uart_init_port(struct pci_dev *pdev,
    if (!rxbuf)
    goto init_port_free_txbuf;

    - base_baud = DEFAULT_BAUD_RATE;
    + uart_clock = DEFAULT_UART_CLOCK;

    /* quirk for CM-iTC board */
    board_name = dmi_get_system_info(DMI_BOARD_NAME);
    if (board_name && strstr(board_name, "CM-iTC"))
    - base_baud = 192000000; /* 192.0MHz */
    + uart_clock = 192000000; /* 192.0MHz */
    +
    + /* The module parameter overrides default and system quirks. */
    + uart_clock = clock_param ? clock_param : uart_clock;

    switch (port_type) {
    case PORT_UNKNOWN:
    @@ -1597,7 +1601,7 @@ static struct eg20t_port *pch_uart_init_port(struct pci_dev *pdev,
    priv->rxbuf.size = PAGE_SIZE;

    priv->fifo_size = fifosize;
    - priv->base_baud = base_baud;
    + priv->uart_clock = uart_clock;
    priv->port_type = PORT_MAX_8250 + port_type + 1;
    priv->port.dev = &pdev->dev;
    priv->port.iobase = iobase;
    @@ -1614,7 +1618,7 @@ static struct eg20t_port *pch_uart_init_port(struct pci_dev *pdev,
    spin_lock_init(&priv->port.lock);

    pci_set_drvdata(pdev, priv);
    - pch_uart_hal_request(pdev, fifosize, base_baud);
    + pch_uart_hal_request(pdev, fifosize, uart_clock);

    #ifdef CONFIG_SERIAL_PCH_UART_CONSOLE
    pch_uart_ports[board->line_no] = priv;
    @@ -1785,3 +1789,4 @@ module_exit(pch_uart_module_exit);
    MODULE_LICENSE("GPL v2");
    MODULE_DESCRIPTION("Intel EG20T PCH UART PCI Driver");
    module_param(default_baud, uint, S_IRUGO);
    +module_param(clock_param, uint, S_IRUGO);
    --
    1.7.6.5

    --
    Darren Hart
    Intel Open Source Technology Center
    Yocto Project - Linux Kernel


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