linux-kernel - Re: [PATCH RFC 2/2] serial: 8250: Add PRUSS UART driver

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Message-ID: <cd88db5d-a792-488a-98c0-678aed8e3559@ti.com>
Date: Mon, 12 May 2025 19:06:43 -0500
From: Judith Mendez <jm@...com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kevin Hilman
	<khilman@...libre.com>,
        Jiri Slaby <jirislaby@...nel.org>, <linux-kernel@...r.kernel.org>,
        <linux-serial@...r.kernel.org>, Hari Nagalla
	<hnagalla@...com>
Subject: Re: [PATCH RFC 2/2] serial: 8250: Add PRUSS UART driver

Hi Andy,

On 5/9/25 6:43 AM, Andy Shevchenko wrote:
> On Thu, May 08, 2025 at 05:09:03PM -0500, Judith Mendez wrote:
>> On 5/2/25 4:50 AM, Andy Shevchenko wrote:
>>> On Wed, Apr 30, 2025 at 07:31:13PM -0500, Judith Mendez wrote:

...
>>>> +	/* Old custom speed handling */
>>>> +	if (baud == 38400 && (port->flags & UPF_SPD_MASK) == UPF_SPD_CUST) {
>>>> +		quot = port->custom_divisor & UART_DIV_MAX;
>>>> +		if (port->custom_divisor & (1 << 16))
>>>> +			*frac = PRUSS_UART_MDR_13X_MODE;
>>>> +		else
>>>> +			*frac = PRUSS_UART_MDR_16X_MODE;
>>>> +
>>>> +		return quot;
>>>> +	}
>>>
>>> Why?! Please, try to avoid adding more drivers with this ugly hack.
>>
>> My understanding is that this is not a hack, for 38400 we need to pass
>> as custom baud. What is the alternative here?
> 
> BOTHER. The 38400 is a hack, you lie to the stakeholders that you are at 38.4,
> while in real life it means anything.
> 
>> I see other drivers are doing this as well, will look into this further
>> but not sure if there is a better solution for this.
> 
> BOTHER is the solution. Not perfect, but the existing one.


Thanks for the hint, I have removed the hack from the driver and will be
sending v1. thanks.

~ Judith