linux-kernel - Re: [PATCH v4 0/2] microchip-tcb-capture: Add Capture, Compare, Overflow etc. events

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Message-ID: <Z8B1LDT-n2XTTp8q@ishi>
Date: Thu, 27 Feb 2025 23:22:36 +0900
From: William Breathitt Gray <wbg@...nel.org>
To: Kamel Bouhara <kamel.bouhara@...tlin.com>
Cc: Csókás Bence <csokas.bence@...lan.hu>,
	linux-arm-kernel@...ts.infradead.org, linux-iio@...r.kernel.org,
	linux-kernel@...r.kernel.org, Dharma.B@...rochip.com,
	Ludovic Desroches <ludovic.desroches@...rochip.com>,
	Nicolas Ferre <nicolas.ferre@...rochip.com>,
	Jonathan Cameron <jic23@...nel.org>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	Alexandre Belloni <alexandre.belloni@...tlin.com>
Subject: Re: [PATCH v4 0/2] microchip-tcb-capture: Add Capture, Compare,
 Overflow etc. events

On Thu, Feb 27, 2025 at 02:53:30PM +0100, Kamel Bouhara wrote:
> On Thu, Feb 27, 2025 at 01:59:57PM +0900, William Breathitt Gray wrote:
> > Let me make sure I understand the situation correctly. This SoC has two
> > Timer Counter Blocks (TCB) and each TCB has three Timer Counter Channels
> > (TCC); each TCC has a Counter Value (CV) and three general registers
> > (RA, RB, RC); RA and RB can store Captures, and RC can be used for
> > Compare operations.
> >
> > If that is true, then the correct way for this hardware to be exposed is
> > to have each TCB be a Counter device where each TCC is exposed as a
> > Count. So for this SoC: two Counter devices as counter0 and counter1;
> > count0, count1, and count2 as the three TCC; i.e. counter0/count{0,1,2}
> > and counter1/count{0,1,2}.

[...]

> > Kamel, what would it take for us to rectify this situation so that the
> > TCC are organized together by TCB under the same Counter devices?
> 
> Hello,
> 
> Indeed, each TCC operates independently except when quadrature mode is
> enabled. I assume this approach was taken to provide more flexibility by
> exposing them separately.
> 
> Currently only one channel is configured this would need to rework the
> driver to make the 3 TCCs exposed.
> 
> Greetings,
> Kamel

Skimming through the driver, it looks like what we'll need is for
mchp_tc_counts[] to have all three TCCs defined, then have
mchp_tc_probe() match on a TCB node and configure each TCC. Once that's
setup, then whenever we need to identify which TCC a callback is
exposing, we can get it from count->id.

So for example, the TC_CV register offset is calculated as 0x00 +
channel * 0x40 + 0x10. In the count_read() callback we can leverage
count->id to identify the TCC and thus get the respective TC_CV register
at offset + count->id * 0x40 + 0x10.

William Breathitt Gray

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