linux-kernel - Re: [PATCH v3 0/2] switch to atomic PWM

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Date:   Thu, 6 Apr 2017 16:33:19 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Claudiu Beznea <claudiu.beznea@...rochip.com>
Cc:     robh+dt@...nel.org, pawel.moll@....com, mark.rutland@....com,
        ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
        boris.brezillon@...e-electrons.com,
        alexandre.belloni@...e-electrons.com, linux-pwm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, nicolas.ferre@...rochip.com,
        cristian.birsan@...rochip.com, andrei.pistirica@...rochip.com,
        tudor.ambarus@...rochip.com, eugen.hristev@...rochip.com
Subject: Re: [PATCH v3 0/2] switch to atomic PWM

On Wed, Mar 22, 2017 at 03:29:33PM +0200, Claudiu Beznea wrote:
> Changes in v3:
> - since v2 introduced per-IP register layout there is no need
> to keep update_cdty and set_cprd_cdty members in atmel_pwm_data
> data structure used in v2; doing in this way the atmel_pwm_data
> data structure will remain with only one member, regs. To avoid
> another level of indirection, the atmel_pwm_data has been removed
> and only atmel_pwm_registers data structure has been keept. In
> this way, "data" member of atmel_pwm_chip data structure was
> replaced by "regs" member; due to these changes prototype of
> atmel_pwm_get_driver_data() function was also changed;
> also, driver private data variables were renamed in the following
> format "atmel_pwm_regs_v*"
> - there is no need for the following checks at the begining
> of atmel_pwm_apply() which were present in v2:
> 
> 	if (cstate.enabled &&
> 	    (cstate.polarity != state->polarity ||
> 	     cstate.period != state->period))
> 		pwm_reset = true;
> 
> it is enough to add:
> 
> 	if (state->enabled) {
> 		if (cstate.enabled &&
> 		    cstate.polarity == state->polarity &&
> 		    cstate.period == state->period) {
> 
> inside "if (state->enabled)" block and also to check cstate.enabled
> instead of checking pwm_reset variable introduced in v2:
> 
> 		if (cstate.enabled) {
> 			atmel_pwm_disable(chip, pwm, false);
> 		} else {
> 			ret = clk_enable(atmel_pwm->clk);
> 			if (ret) {
> 				dev_err(chip->dev, "failed to enable clock\n");
> 				return ret;
> 			}
> 		}
> 
> Changes in v2:
> - update only duty factor without disabling the PWM channel
> - if PWM channel is enabled, period, as signal polarity, is
> updated by disabling + enabling the PWM channel
> - atmel_pwm_config_prepare() function has been removed and
> added instead two functions, one to compute the CPRD+Prescaler
> (atmel_pwm_calculate_cprd_and_pres()), one to compute CRDY
> (atmel_pwm_calculate_cdty())
> - atmel_pwm_config_set() body was directly moved to atmel_pwm_apply()
> - add 3 new members to atmel_pwm_data: update_cdty, set_cprd_cdty and
> regs:
> 	- update_cdty is called to configure duty factor without
> 	disabling PWM channel, when necessary
> 	- set_cprd_cdty is called to configure both period and
> 	duty factor parameters
> 	- regs keeps the period and duty registers and was added to
> 	have common functions for update_cdty and set_cprd_cdty
> 	members of atmel_pwm_data for all boards;
> - add a new parameter to atmel_pwm_disable(); this will be used in
> updating period + signal polarity by disabling + enabling the
> PWM channel. In this case, there is no need to disable PWM clock
> since new configuration will be imediately applied.
> - adapted the other reviewer comments excepts the one regarding
> "cdty = cprd - cycles;" from atmel_pwm_calculate_cdty() since
> in atmel_pwm_apply(), selecting polarity in the other way arround
> than is currently done in this commit will need the changing of DPOLI
> bit from Channel Mode Register, in order to keep the initial
> output level of PWM channel after disable operation; this works
> for sama5d2 but not for sam9rl which hasn't document the DPOLI
> bit in datasheet; sama5d3 also hasn't document the DPOLI bit in
> datasheet; one option was to have different aproach for different
> boards but the code becomes messy.
> 
> Claudiu Beznea (2):
>   drivers: pwm: pwm-atmel: switch to atomic PWM
>   drivers: pwm: pwm-atmel: enable PWM on sama5d2
> 
>  .../devicetree/bindings/pwm/atmel-pwm.txt          |   1 +
>  drivers/pwm/pwm-atmel.c                            | 276 ++++++++++-----------
>  2 files changed, 133 insertions(+), 144 deletions(-)

Applied, thanks.

Thierry

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