linux-kernel - Re: [External Email] Re: [PATCH v2 1/2] dt-bindings: serial: sc16is7xx: Add description for polling mode

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Message-ID: <23f351a1-4959-4492-9848-940618fdbccf@kernel.org>
Date: Tue, 7 Jan 2025 14:39:18 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Andre Werner <andre.werner@...tec-electronic.com>
Cc: gregkh@...uxfoundation.org, jirislaby@...nel.org,
 hvilleneuve@...onoff.com, andy@...nel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
 lech.perczak@...lingroup.com, krzk+dt@...nel.org, conor+dt@...nel.org,
 robh@...nel.org
Subject: Re: [External Email] Re: [PATCH v2 1/2] dt-bindings: serial:
 sc16is7xx: Add description for polling mode

On 07/01/2025 09:49, Andre Werner wrote:
> Dear Krzysztof,
> 
> On Tue, 7 Jan 2025, Krzysztof Kozlowski wrote:
> 
>> On Mon, Jan 06, 2025 at 09:50:50AM +0100, Andre Werner wrote:
>>> Polling mode is enabled if the "interrupts" property is missing.
>>> Thus, this commit deletes "interrupts" entry from "required" section
>>> and adds a description for the fallback to polling mode at the
>>> "interrupts" entry.
>>
>> Can the device actually operate with interrupt line disconnected? I
>> skimmed through datasheet and they did not mention that as a valid
>> setup.
> 
> For polling mode the datasheet said:
> 
> In Polled mode (IER[3:0] = 0000) the status of the receiver and transmitter can be
> checked by polling the Line Status Register (LSR). This mode is an alternative to the FIFO
> Interrupt mode of operation where the status of the receiver and transmitter is
> automatically known by means of interrupts sent to the CPU.

I guess this would mean that line can be physically disconnected.

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>

Best regards,
Krzysztof