From: Thierry Reding <thierry.reding@gmail.com>
To: Rajkumar Rampelli <rrajk@nvidia.com>
Cc: robh+dt@kernel.org, mark.rutland@arm.com, jonathanh@nvidia.com,
jdelvare@suse.com, linux@roeck-us.net, corbet@lwn.net,
catalin.marinas@arm.com, will.deacon@arm.com,
kstewart@linuxfoundation.org, gregkh@linuxfoundation.org,
pombredanne@nexb.com, mmaddireddy@nvidia.com,
mperttunen@nvidia.com, arnd@arndb.de, timur@codeaurora.org,
andy.gross@linaro.org, xuwei5@hisilicon.com, elder@linaro.org,
heiko@sntech.de, krzk@kernel.org, ard.biesheuvel@linaro.org,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-pwm@vger.kernel.org, linux-tegra@vger.kernel.org,
linux-hwmon@vger.kernel.org, linux-doc@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, ldewangan@nvidia.com
Subject: Re: [PATCH V2 1/9] pwm: core: Add support for PWM HW driver with pwm capture only
Date: Mon, 30 Apr 2018 11:51:59 +0200 [thread overview]
Message-ID: <20180430095159.GD2476@ulmo> (raw)
In-Reply-To: <1521607244-29734-2-git-send-email-rrajk@nvidia.com>
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On Wed, Mar 21, 2018 at 10:10:36AM +0530, Rajkumar Rampelli wrote:
> Add support for pwm HW driver which has only capture functionality.
> This helps to implement the PWM based Tachometer driver which reads
> the PWM output signals from electronic fans.
>
> PWM Tachometer captures the period and duty cycle of the PWM signal
>
> Add conditional checks for callabacks enable(), disable(), config()
> to check if they are supported by the client driver or not. Skip these
> callbacks if they are not supported.
>
> Signed-off-by: Rajkumar Rampelli <rrajk@nvidia.com>
> ---
>
> V2: Added if conditional checks for pwm callbacks since drivers may
> implements only pwm capture functionality.
>
> drivers/pwm/core.c | 21 +++++++++++++++------
> 1 file changed, 15 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
> index 1581f6a..f70fe68 100644
> --- a/drivers/pwm/core.c
> +++ b/drivers/pwm/core.c
> @@ -246,6 +246,10 @@ static bool pwm_ops_check(const struct pwm_ops *ops)
> if (ops->apply)
> return true;
>
> + /* driver supports capture operation */
> + if (ops->capture)
> + return true;
> +
> return false;
> }
>
> @@ -495,7 +499,8 @@ int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state)
> * ->apply().
> */
> if (pwm->state.enabled) {
> - pwm->chip->ops->disable(pwm->chip, pwm);
> + if (pwm->chip->ops->disable)
> + pwm->chip->ops->disable(pwm->chip, pwm);
This is not a good idea. It means that you'll be able to successfully
configure a capture-only PWM channel for output. I think all of the
output configuration functions should return an error (-ENOSYS?) for
capture-only devices, much like we return -ENOSYS for pwm_capture() if
the driver doesn't implement capture support.
Thierry
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next prev parent reply other threads:[~2018-04-30 9:51 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-21 4:40 [PATCH V2 0/9] Implementation of Tegra Tachometer driver Rajkumar Rampelli
2018-03-21 4:40 ` [PATCH V2 1/9] pwm: core: Add support for PWM HW driver with pwm capture only Rajkumar Rampelli
2018-04-30 9:51 ` Thierry Reding [this message]
2018-03-21 4:40 ` [PATCH V2 2/9] arm64: tegra: Add PWM controller on Tegra186 soc Rajkumar Rampelli
2018-03-21 4:40 ` [PATCH V2 3/9] dt-bindings: Tegra186 tachometer device tree bindings Rajkumar Rampelli
2018-03-27 14:52 ` Rob Herring
2018-03-27 15:00 ` Rob Herring
2018-04-09 5:38 ` Mikko Perttunen
2018-04-09 13:21 ` Rob Herring
2018-04-09 14:37 ` Mikko Perttunen
2018-04-10 13:30 ` Rob Herring
2018-04-10 13:43 ` Guenter Roeck
2018-03-21 4:40 ` [PATCH V2 4/9] arm64: tegra: Add Tachometer Controller on Tegra186 Rajkumar Rampelli
2018-03-21 4:40 ` [PATCH V2 5/9] pwm: tegra: Add PWM based Tachometer driver Rajkumar Rampelli
2018-03-21 4:40 ` [PATCH V2 6/9] arm64: tegra: Add pwm based fan support on Tegra186 Rajkumar Rampelli
2018-03-21 4:40 ` [PATCH V2 7/9] hwmon: pwm-fan: add sysfs node to read rpm of fan Rajkumar Rampelli
2018-03-21 6:09 ` Guenter Roeck
2018-03-21 4:40 ` [PATCH V2 8/9] arm64: defconfig: enable Nvidia Tegra Tachometer as a module Rajkumar Rampelli
2018-03-21 4:40 ` [PATCH V2 9/9] arm64: defconfig: enable pwm-fan as a loadable module Rajkumar Rampelli
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