From: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp> To: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de> Cc: Rob Herring <robh+dt@kernel.org>, Thierry Reding <thierry.reding@gmail.com>, Lee Jones <lee.jones@linaro.org>, devicetree@vger.kernel.org, linux-pwm@vger.kernel.org, punit1.agrawal@toshiba.co.jp, yuji2.ishikawa@toshiba.co.jp, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 2/2] pwm: visconti: Add Toshiba Visconti SoC PWM support Date: Sun, 18 Apr 2021 20:07:18 +0900 [thread overview] Message-ID: <20210418110718.4zrh665anbz3wmqc@toshiba.co.jp> (raw) In-Reply-To: <20210417155009.vnqxx3fn2yjzp3qc@pengutronix.de> Hi Uwe, On Sat, Apr 17, 2021 at 05:50:09PM +0200, Uwe Kleine-König wrote: > Hello Nobuhiro, > > On Fri, Apr 16, 2021 at 09:15:23PM +0900, Nobuhiro Iwamatsu wrote: > > > > > For me the critical (and only) difference between "off" and > > > > > "duty cycle = 0" is that when a new configuration is to be applied. In > > > > > the "off" state a new period can (and should) start immediately, while > > > > > with "duty_cycle = 0" the rising edge should be delayed until the > > > > > currently running period is over.[1] > > > > > > > > > > So the thing to do here (IMHO) is: > > > > > > > > > > Iff with PIPGM_PCSR = 0 configuring a new setting (that is finalized > > > > > with writing a non-zero value to PIPGM_PCSR) completes the currently > > > > > running period, then always assume the PWM as enabled. > > > > > > > > Yes, this device works that way. > > > > > > OK, then please use > > > > > > state->enabled = true > > > > > > unconditionally in visconti_pwm_get_state(). > > > > Please let me check. > > If I unconditionally add 'state->enabled = true' to visconti_pwm_get_state(), > > state->enabled is set to true because visconti_pwm_get_state() is called when > > the device is created (this is when I write the device number to the export of > > /sys/class/pwm/pwmchip0 ). > > And since PIPGM_PCSR is 0 in this state, the pulse by PWM is not output. > > A PWM that is currently configured with .enabled = true and .duty_cycle > = 0 doesn't have a pulse, so this is fine. > I understood, thanks. > > However, I think this means that the device is working as this driver. > > I don't understand this sentence. The description of the struct pwm_state says "PWM enabled status". I thought 'state-> enabled' would hold the working state of the hardware. > > Best regards > Uwe Best regards, Nobuhiro
WARNING: multiple messages have this Message-ID (diff)
From: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp> To: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de> Cc: Rob Herring <robh+dt@kernel.org>, Thierry Reding <thierry.reding@gmail.com>, Lee Jones <lee.jones@linaro.org>, devicetree@vger.kernel.org, linux-pwm@vger.kernel.org, punit1.agrawal@toshiba.co.jp, yuji2.ishikawa@toshiba.co.jp, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 2/2] pwm: visconti: Add Toshiba Visconti SoC PWM support Date: Sun, 18 Apr 2021 20:07:18 +0900 [thread overview] Message-ID: <20210418110718.4zrh665anbz3wmqc@toshiba.co.jp> (raw) In-Reply-To: <20210417155009.vnqxx3fn2yjzp3qc@pengutronix.de> Hi Uwe, On Sat, Apr 17, 2021 at 05:50:09PM +0200, Uwe Kleine-König wrote: > Hello Nobuhiro, > > On Fri, Apr 16, 2021 at 09:15:23PM +0900, Nobuhiro Iwamatsu wrote: > > > > > For me the critical (and only) difference between "off" and > > > > > "duty cycle = 0" is that when a new configuration is to be applied. In > > > > > the "off" state a new period can (and should) start immediately, while > > > > > with "duty_cycle = 0" the rising edge should be delayed until the > > > > > currently running period is over.[1] > > > > > > > > > > So the thing to do here (IMHO) is: > > > > > > > > > > Iff with PIPGM_PCSR = 0 configuring a new setting (that is finalized > > > > > with writing a non-zero value to PIPGM_PCSR) completes the currently > > > > > running period, then always assume the PWM as enabled. > > > > > > > > Yes, this device works that way. > > > > > > OK, then please use > > > > > > state->enabled = true > > > > > > unconditionally in visconti_pwm_get_state(). > > > > Please let me check. > > If I unconditionally add 'state->enabled = true' to visconti_pwm_get_state(), > > state->enabled is set to true because visconti_pwm_get_state() is called when > > the device is created (this is when I write the device number to the export of > > /sys/class/pwm/pwmchip0 ). > > And since PIPGM_PCSR is 0 in this state, the pulse by PWM is not output. > > A PWM that is currently configured with .enabled = true and .duty_cycle > = 0 doesn't have a pulse, so this is fine. > I understood, thanks. > > However, I think this means that the device is working as this driver. > > I don't understand this sentence. The description of the struct pwm_state says "PWM enabled status". I thought 'state-> enabled' would hold the working state of the hardware. > > Best regards > Uwe Best regards, Nobuhiro _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-04-18 11:08 UTC|newest] Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-04-09 23:08 [PATCH v4 0/2] pwm: visconti: Add Toshiba Visconti SoC PWM support Nobuhiro Iwamatsu 2021-04-09 23:08 ` Nobuhiro Iwamatsu 2021-04-09 23:08 ` [PATCH v4 1/2] dt-bindings: pwm: Add bindings for Toshiba Visconti PWM Controller Nobuhiro Iwamatsu 2021-04-09 23:08 ` Nobuhiro Iwamatsu 2021-04-09 23:08 ` [PATCH v4 2/2] pwm: visconti: Add Toshiba Visconti SoC PWM support Nobuhiro Iwamatsu 2021-04-09 23:08 ` Nobuhiro Iwamatsu 2021-04-10 1:57 ` kernel test robot 2021-04-10 13:53 ` Uwe Kleine-König 2021-04-10 13:53 ` Uwe Kleine-König 2021-04-12 2:55 ` Nobuhiro Iwamatsu 2021-04-12 2:55 ` Nobuhiro Iwamatsu 2021-04-12 7:02 ` Uwe Kleine-König 2021-04-12 7:02 ` Uwe Kleine-König 2021-04-16 8:07 ` Nobuhiro Iwamatsu 2021-04-16 8:07 ` Nobuhiro Iwamatsu 2021-04-16 9:44 ` Uwe Kleine-König 2021-04-16 9:44 ` Uwe Kleine-König 2021-04-16 12:15 ` Nobuhiro Iwamatsu 2021-04-16 12:15 ` Nobuhiro Iwamatsu 2021-04-17 15:50 ` Uwe Kleine-König 2021-04-17 15:50 ` Uwe Kleine-König 2021-04-18 11:07 ` Nobuhiro Iwamatsu [this message] 2021-04-18 11:07 ` Nobuhiro Iwamatsu 2021-04-10 18:52 ` Uwe Kleine-König 2021-04-10 18:52 ` Uwe Kleine-König 2021-04-12 3:04 ` Nobuhiro Iwamatsu 2021-04-12 3:04 ` Nobuhiro Iwamatsu
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