Re: [PATCH v2 3/7] serial: exar: add support for config/set single MPIO

Ilpo Järvinen
2024-04-12T10:20:49Z

On Thu, 11 Apr 2024, parker@finest.io wrote:

> From: Parker Newman <pnewman@connecttech.com>
>
> Adds support for configuring and setting a single MPIO
>
> Signed-off-by: Parker Newman <pnewman@connecttech.com>
> ---
> drivers/tty/serial/8250/8250_exar.c | 88 +++++++++++++++++++++++++++++
> 1 file changed, 88 insertions(+)
>
> diff --git a/drivers/tty/serial/8250/8250_exar.c b/drivers/tty/serial/8250/8250_exar.c
> index 49d690344e65..9915a99cb7c6 100644
> --- a/drivers/tty/serial/8250/8250_exar.c
> +++ b/drivers/tty/serial/8250/8250_exar.c
> @@ -305,6 +305,94 @@ static int exar_ee_read(struct exar8250 *priv, uint8_t ee_addr)
> return data;
> }
>
> +/**
> + * exar_mpio_config() - Configure an EXar MPIO as input or output
> + * @priv: Device's private structure
> + * @mpio_num: MPIO number/offset to configure
> + * @output: Configure as output if true, inout if false
> + *
> + * Configure a single MPIO as an input or output and disable trisate.

tristate

> + * If configuring as output it is reccomended to set value with
> + * exar_mpio_set prior to calling this function to ensure default state.

Use () if talking about function.

> + *
> + * Return: 0 on success, negative error code on failure
> + */
> +static int exar_mpio_config(struct exar8250 *priv,
> + unsigned int mpio_num, bool output)
> +{
> + uint8_t sel_reg; //MPIO Select register (input/output)
> + uint8_t tri_reg; //MPIO Tristate register
> + uint8_t value;
> + unsigned int bit;
> +
> + if (mpio_num < 8) {
> + sel_reg = UART_EXAR_MPIOSEL_7_0;
> + tri_reg = UART_EXAR_MPIO3T_7_0;
> + bit = mpio_num;
> + } else if (mpio_num >= 8 && mpio_num < 16) {
> + sel_reg = UART_EXAR_MPIOSEL_15_8;
> + tri_reg = UART_EXAR_MPIO3T_15_8;
> + bit = mpio_num - 8;
> + } else {
> + return -EINVAL;
> + }
> +
> + //Disable MPIO pin tri-state
> + value = exar_read_reg(priv, tri_reg);
> + value &= ~(BIT(bit));

Use more meaningful variable name than "bit", it could perhaps even avoid
the need to use the comment if the code is self-explanary with better
variable name.

> + exar_write_reg(priv, tri_reg, value);
> +
> + value = exar_read_reg(priv, sel_reg);
> + //Set MPIO as input (1) or output (0)

Unnecessary comment.

> + if (output)
> + value &= ~(BIT(bit));

Unnecessary parenthesis.

> + else
> + value |= BIT(bit);
> +
> + exar_write_reg(priv, sel_reg, value);

Don't leave empty line into RMW sequence.

> +
> + return 0;
> +}
> +/**
> + * exar_mpio_set() - Set an Exar MPIO output high or low
> + * @priv: Device's private structure
> + * @mpio_num: MPIO number/offset to set
> + * @high: Set MPIO high if true, low if false
> + *
> + * Set a single MPIO high or low. exar_mpio_config must also be called
> + * to configure the pin as an output.
> + *
> + * Return: 0 on success, negative error code on failure
> + */
> +static int exar_mpio_set(struct exar8250 *priv,
> + unsigned int mpio_num, bool high)
> +{
> + uint8_t reg;
> + uint8_t value;
> + unsigned int bit;
> +
> + if (mpio_num < 8) {
> + reg = UART_EXAR_MPIOSEL_7_0;
> + bit = mpio_num;
> + } else if (mpio_num >= 8 && mpio_num < 16) {
> + reg = UART_EXAR_MPIOSEL_15_8;
> + bit = mpio_num - 8;
> + } else {
> + return -EINVAL;
> + }
> +
> + value = exar_read_reg(priv, reg);
> +
> + if (high)
> + value |= BIT(bit);
> + else
> + value &= ~(BIT(bit));

Extra parenthesis.

> +
> + exar_write_reg(priv, reg, value);

Again, I'd put this kind of simple RMW sequence without newlines.

> +
> + return 0;
> +}

There are zero users of these functions so I couldn't review if two
functions are really needed, or if the difference could be simply handled
using a boolean parameter.

--
i.