Re: [PATCH 1/2] pwm: make it possible to apply pwm changes in atomic context - Uwe Kleine-König

From: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
To: Thierry Reding <thierry.reding@gmail.com>
Cc: linux-arm-kernel@lists.infradead.org, linux-pwm@vger.kernel.org,
	Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Sean Young <sean@mess.org>,
	Daire McNamara <daire.mcnamara@microchip.com>,
	Shawn Guo <shawnguo@kernel.org>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	Alexandre Torgue <alexandre.torgue@foss.st.com>,
	Vladimir Zapolskiy <vz@mleia.com>,
	Conor Dooley <conor.dooley@microchip.com>,
	Fabrice Gasnier <fabrice.gasnier@foss.st.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	NXP Linux Team <linux-imx@nxp.com>,
	Pengutronix Kernel Team <kernel@pengutronix.de>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	linux-riscv@lists.infradead.org,
	Fabio Estevam <festevam@gmail.com>,
	linux-stm32@st-md-mailman.stormreply.com,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] pwm: make it possible to apply pwm changes in atomic context
Date: Fri, 6 Oct 2023 16:44:56 +0200	[thread overview]
Message-ID: <20231006144456.zybxv2pn4c37fpr3@pengutronix.de> (raw)
In-Reply-To: <ZR_hJ05h5O6SpM_D@orome.fritz.box>

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Hello Thierry,

On Fri, Oct 06, 2023 at 12:27:51PM +0200, Thierry Reding wrote:
> On Wed, Oct 04, 2023 at 11:59:20AM +0200, Uwe Kleine-König wrote:
> > On Sun, Oct 01, 2023 at 11:40:29AM +0100, Sean Young wrote:
> > > diff --git a/drivers/pwm/pwm-fsl-ftm.c b/drivers/pwm/pwm-fsl-ftm.c
> > > index b7c6045c5d08..b8b9392844e9 100644
> > > --- a/drivers/pwm/pwm-fsl-ftm.c
> > > +++ b/drivers/pwm/pwm-fsl-ftm.c
> > > @@ -405,6 +405,7 @@ static int fsl_pwm_probe(struct platform_device *pdev)
> > >  
> > >  	fpc->soc = of_device_get_match_data(&pdev->dev);
> > >  	fpc->chip.dev = &pdev->dev;
> > > +	fpc->chip.can_sleep = true;
> > 
> > As .apply() being callable in non-sleepable context only depends on
> > .apply() I think a better place for this property is in struct pwm_ops.
> 
> What about drivers for devices that can be either sleeping or not? There
> are things like regmap which can abstract those differences away, so you
> could have a driver that works on both types of devices, so setting this
> in ops wouldn't be correct all the time. I think can_sleep needs to be
> per-chip rather than per-driver.

I would consider that a theoretic possibility. If there is a hardware
that has a (say) i2c and a memory-mapped register variant, I never
encountered such a thing. Hmm, the dwc driver seems to have a pci and a
memory-mapped variant, both would be "fast" though. (Wouldn't they?)

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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