From: David Lechner <david@lechnology.com>
To: William Breathitt Gray <vilhelm.gray@gmail.com>
Cc: linux-iio@vger.kernel.org, linux-omap@vger.kernel.org,
devicetree@vger.kernel.org, "Rob Herring" <robh+dt@kernel.org>,
"Mark Rutland" <mark.rutland@arm.com>,
"Benoît Cousson" <bcousson@baylibre.com>,
"Tony Lindgren" <tony@atomide.com>,
"Thierry Reding" <thierry.reding@gmail.com>,
linux-kernel@vger.kernel.org, linux-pwm@vger.kernel.org
Subject: Re: [PATCH 2/4] counter: new TI eQEP driver
Date: Fri, 2 Aug 2019 11:17:11 -0500 [thread overview]
Message-ID: <680ed555-c5db-6640-8fd3-121422077eff@lechnology.com> (raw)
In-Reply-To: <20190802092727.GB30522@icarus>
On 8/2/19 4:27 AM, William Breathitt Gray wrote:
>> +static const struct counter_ops ti_eqep_counter_ops = {
>> + .count_read = ti_eqep_count_read,
>> + .count_write = ti_eqep_count_write,
>> + .function_get = ti_eqep_function_get,
>> + .function_set = ti_eqep_function_set,
>> +};
> Are you able to provide a signal_read function, or are the Signals not
> exposed to the user by this device? Sometimes quadrature encoder devices
> provide an instanteous read of the signal lines to tell whether they are
> high or low, so I figured I'd ask.
No, it does not look like these signals can be read directly.
>
> You should define an action_get function as well along with Synapses
> corresponding to each Signal. This will allow users to know whether the
> Synapse fires on a rising edge, falling edge, no edge, or both edges.
>
> For example, consider the drivers/counter/104-quad-8.c file. Each count
> register has three associated signal lines: Quadrature A, Quadrature B,
> and Index.
>
> Quadrature A and B are your typical quadrature encoder lines and
> depending on the function mode selected (quadrature x4, pulse-direction,
> etc.) could have a Synapse action mode of none, rising edge, falling
> edge, or both edges; see the quad8_synapse_actions_list array.
>
> In contrast, the Index signal line only has two Synapse action modes:
> rising edge (in the case preset functionality is enabled) or none.
The encoders I have don't use the index or strobe signals, so I was
thinking maybe I should omit those two signals from the driver for the
time being since I don't have a way of testing.
>
> For the TI eQEP driver, there will be four Synapses corresponding to the
> four Signals: QEPA, QEPB, QEPI, and QEPS. See if you are able to
> implement the Synapses and action_get function by using the 104-quad-8.c
> file as a reference. That file does have a lot of extra functionality
> tossed in compared to yours, so if you have trouble groking it, just let
> me know and I'll try to help.
>
next prev parent reply other threads:[~2019-08-02 16:17 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-22 15:45 [PATCH 0/4] new driver for TI eQEP David Lechner
2019-07-22 15:45 ` [PATCH 1/4] dt-bindings: counter: new bindings " David Lechner
2019-07-27 19:48 ` Jonathan Cameron
2019-08-02 7:25 ` William Breathitt Gray
2019-08-02 13:34 ` Rob Herring
2019-08-02 13:58 ` William Breathitt Gray
2019-07-22 15:45 ` [PATCH 2/4] counter: new TI eQEP driver David Lechner
2019-07-30 12:35 ` Uwe Kleine-König
2019-07-30 15:28 ` David Lechner
2019-08-02 9:27 ` William Breathitt Gray
2019-08-02 16:09 ` David Lechner
2019-08-02 16:17 ` David Lechner [this message]
2019-08-02 16:40 ` William Breathitt Gray
2019-07-22 15:45 ` [PATCH 3/4] ARM: dts: am33xx: Add nodes for eQEP David Lechner
2019-07-23 8:42 ` Tony Lindgren
2019-07-23 14:45 ` David Lechner
2019-07-23 14:51 ` Tony Lindgren
2019-07-22 15:45 ` [PATCH 4/4] ARM: dts: am335x-boneblue: Enable eQEP David Lechner
2019-07-25 12:40 ` [PATCH 0/4] new driver for TI eQEP William Breathitt Gray
2019-07-25 22:52 ` David Lechner
2019-07-27 19:45 ` Jonathan Cameron
2019-07-30 4:45 ` William Breathitt Gray
2019-08-01 17:37 ` David Lechner
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