linux-kernel - Re: [PATCH V4] pwm: tegra: dynamic clk freq configuration by PWM driver

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Message-ID: <20200602124758.GE3360525@ulmo>
Date:   Tue, 2 Jun 2020 14:47:58 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Sandipan Patra <spatra@...dia.com>
Cc:     treding@...dia.com, jonathanh@...dia.com,
        u.kleine-koenig@...gutronix.de, bbasu@...dia.com,
        ldewangan@...dia.com, kyarlagadda@...dia.com,
        linux-pwm@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V4] pwm: tegra: dynamic clk freq configuration by PWM
 driver

On Mon, Jun 01, 2020 at 10:50:36AM +0530, Sandipan Patra wrote:
> Added support for dynamic clock freq configuration in pwm kernel driver.
> Earlier the pwm driver used to cache boot time clock rate by pwm clock
> parent during probe. Hence dynamically changing pwm frequency was not
> possible for all the possible ranges. With this change, dynamic calculation
> is enabled and it is able to set the requested period from sysfs knob
> provided the value is supported by clock source.
> 
> Changes mainly have 2 parts:
>   - T186 and later chips [1]
>   - T210 and prior chips [2]
> 
> For [1] - Changes implemented to set pwm period dynamically and
>           also checks added to allow only if requested period(ns) is
>           below or equals to higher range.
> 
> For [2] - Only checks if the requested period(ns) is below or equals
>           to higher range defined by max clock limit. The limitation
>           in T210 or prior chips are due to the reason of having only
>           one pwm-controller supporting multiple channels. But later
>           chips have multiple pwm controller instances each having
> 	  single channel support.
> 
> Signed-off-by: Sandipan Patra <spatra@...dia.com>
> ---
> PATCH V4:
> 1. Code comments fixes
> 
> PATCH V3:
> 1. Return -EINVAL if requested period does not fall inside limit.
> 2. Store the new clock rate for further references.
> 3. Variable name change reverted.
> 4. Comments corrected and new comments are added.
> 
> PATCH V2:
> 1. Maximum frequency calculation is moved to probe.
> 2. Added descriptions for PWM register bits and functional behavior
>    of the controller when new configuration is applied.
> 3. Setting period with possible value when supplied period is below limit.
> 4. Corrected the earlier code comment:
>    plus 1 instead of minus 1 during pwm calculation
> 
>  drivers/pwm/pwm-tegra.c | 80 ++++++++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 76 insertions(+), 4 deletions(-)

Applied, thanks.

Thierry

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