linux-kernel - Re: [PATCH v3 06/10] counter: stm32-timer-cnt: add checks on quadrature encoder capability

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Date: Mon, 8 Jan 2024 16:59:05 +0000
From: William Breathitt Gray <william.gray@...aro.org>
To: Fabrice Gasnier <fabrice.gasnier@...s.st.com>
Cc: lee@...nel.org, alexandre.torgue@...s.st.com, linux-iio@...r.kernel.org,
	linux-stm32@...md-mailman.stormreply.com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 06/10] counter: stm32-timer-cnt: add checks on
 quadrature encoder capability

On Wed, Dec 20, 2023 at 03:57:22PM +0100, Fabrice Gasnier wrote:
> This is a precursor patch to support capture channels on all possible
> channels and stm32 timer types. Original driver was intended to be used
> only as quadrature encoder and simple counter on internal clock.
> 
> So, add a check on encoder capability, so the driver may be probed for
> timer instances without encoder feature. This way, all timers may be used
> as simple counter on internal clock, starting from here.
> 
> Encoder capability is retrieved by using the timer index (originally in
> stm32-timer-trigger driver and dt-bindings). The need to keep backward
> compatibility with existing device tree lead to parse aside trigger node.
> 
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...s.st.com>
> ---
> Changes in v3:
> - New patch split from:
>   "counter: stm32-timer-cnt: populate capture channels and check encoder"
> - return -EOPNOTSUPP when encoder function isn't supported by the timer
>   instance.
> ---
>  drivers/counter/stm32-timer-cnt.c | 55 +++++++++++++++++++++++++++++++
>  1 file changed, 55 insertions(+)
> 
> diff --git a/drivers/counter/stm32-timer-cnt.c b/drivers/counter/stm32-timer-cnt.c
> index bf2726dd7f12..6933d42b16bf 100644
> --- a/drivers/counter/stm32-timer-cnt.c
> +++ b/drivers/counter/stm32-timer-cnt.c
> @@ -11,6 +11,7 @@
>  #include <linux/mfd/stm32-timers.h>
>  #include <linux/mod_devicetable.h>
>  #include <linux/module.h>
> +#include <linux/of.h>
>  #include <linux/pinctrl/consumer.h>
>  #include <linux/platform_device.h>
>  #include <linux/types.h>
> @@ -38,6 +39,8 @@ struct stm32_timer_cnt {
>  	u32 max_arr;
>  	bool enabled;
>  	struct stm32_timer_regs bak;
> +	bool has_encoder;
> +	u32 idx;

This idx value is only used temporarily to determine whether the device has
support for encoder mode. Do we really need to store it indefinitely
here?

> +static int stm32_timer_cnt_probe_encoder(struct platform_device *pdev,

This function uses 'pdev' only to access 'dev'. It'll be better to pass
a reference to 'dev' directly instead.

William Breathitt Gray

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