[PATCH RFC 4/9] serial: serial_meson: add minimal non-DM driver

[Ferass El Hafidi]

On Wed Sep 10, 2025 at 8:30 PM UTC, Heinrich Schuchardt wrote:
> On 9/10/25 22:14, Ferass El Hafidi wrote:
>> On Wed Sep 10, 2025 at 7:53 PM UTC, Heinrich Schuchardt wrote:
>>> <...>
>>>> +static int meson_serial_getc(void)
>>>> +{
>>>> +	struct meson_uart *const uart = (struct meson_uart *)CONFIG_VAL(DEBUG_UART_BASE);
>>>> +	uint32_t status = readl(&uart->status);
>>>> +
>>>> +	if (status & AML_UART_RX_EMPTY)
>>>> +		return -EAGAIN;
>>>> +
>>>> +	if (status & AML_UART_ERR) {
>>>> +		u32 val = readl(&uart->control);
>>>> +
>>>> +		/* Clear error */
>>>> +		val |= AML_UART_CLR_ERR;
>>>> +		writel(val, &uart->control);
>>>> +		val &= ~AML_UART_CLR_ERR;
>>>> +		writel(val, &uart->control);
>>>> +
>>>> +		/* Remove spurious byte from fifo */
>>>> +		readl(&uart->rfifo);
>>>> +		return -EIO;
>>>> +	}
>>>> +
>>>> +	return readl(&uart->rfifo) & 0xff;
>>>> +}
>>>> +
>>>> +static int meson_serial_tstc(void)
>>>> +{
>>>> +	struct meson_uart *const uart = (struct meson_uart *)CONFIG_VAL(DEBUG_UART_BASE);
>>>
>>> CONFIG_SPL_DEBUG_UART_BASE only exists for CONFIG_DEBUG_UART=y and
>>> CONFIG_SPL=y. Shall all configurations depend on CONFIG_DEBUG_UART=y?
>>>
>>> Creating this dependency does not look right to me.
>>>
>> 
>> All Amlogic defconfigs have CONFIG_DEBUG_UART enabled, but I can remove
>> the dependency on CONFIG_DEBUG_UART_BASE if you think it doesn't look
>> right.
>
> We should avoid the possibility of build failures for changed configuration.
>
> Will CONFIG_MESON_SERIAL depend on CONFIG_DEBUG_UART
> or will CONFIG_ARCH_MESON select CONFIG_DEBUG_UART?

Then it might be best to not use DEBUG_UART_BASE.  I'll fix that for
next revision.  Thanks!