Re: [PATCH v18 3/4] pwm: Add support for RZ/G2L GPT - Uwe Kleine-König

From: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
To: Biju Das <biju.das.jz@bp.renesas.com>
Cc: "biju.das.au" <biju.das.au@gmail.com>,
	 "linux-pwm@vger.kernel.org" <linux-pwm@vger.kernel.org>,
	"kernel@pengutronix.de" <kernel@pengutronix.de>,
	 Geert Uytterhoeven <geert+renesas@glider.be>,
	Magnus Damm <magnus.damm@gmail.com>,
	 Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@bp.renesas.com>,
	Fabrizio Castro <fabrizio.castro.jz@renesas.com>,
	 "linux-renesas-soc@vger.kernel.org"
	<linux-renesas-soc@vger.kernel.org>,
	Thierry Reding <thierry.reding@gmail.com>,
	 Philipp Zabel <p.zabel@pengutronix.de>
Subject: Re: [PATCH v18 3/4] pwm: Add support for RZ/G2L GPT
Date: Thu, 14 Mar 2024 23:33:22 +0100	[thread overview]
Message-ID: <ipm72ujiqm4k2nuq7a6sdmqdrwjwrn7uyp4brgbvmmb5mgu6ko@ljltsjnljett> (raw)
In-Reply-To: <OSAPR01MB1587400FECDBFDB3E38A594286292@OSAPR01MB1587.jpnprd01.prod.outlook.com>

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Hello,

On Thu, Mar 14, 2024 at 06:10:50PM +0000, Biju Das wrote:
> > On Tue, Feb 20, 2024 at 07:43:17PM +0000, Biju Das wrote:
> > > +
> > > +static inline u64 rzg2l_gpt_mul_u64_u64_div_u64(u64 a, u64 b, u64 c)
> > > +{
> > > +	u64 retval;
> > > +
> > > +	if (a > b)
> > > +		retval = mul_u64_u64_div_u64(b, a, c);
> > > +	else
> > > +		retval = mul_u64_u64_div_u64(a, b, c);
> > 
> > With
> > https://lore.kernel.org/lkml/20240303092408.662449-2-u.kleine-koenig@pengutronix.de
> > this function can be replaced by a direct call to mul_u64_u64_div_u64().
> > I expect this patch to go into v6.9-rc1 as akpm picked it up before the merge window opened.
> 
> Ok, I will hold next version until v6.9-rc1 as for-pwm-nexxt doesn't have this patch??

I will rebase the stuff for the v6.10-rc1 merge window on v6.9-rc1, so
(assuming my guess is right) you can profit of the improved
mul_u64_u64_div_u64() call. (And even if the patch will go in later, we
can live with the inexact configuration for that period.)

> > > +static u32 rzg2l_gpt_calculate_pv_or_dc(u64 period_or_duty_cycle, u8
> > > +prescale) {
> > > +	return min_t(u64, (period_or_duty_cycle + (1 << (2 * prescale)) - 1) >> (2 * prescale),
> > > +		     U32_MAX);
> > 
> > Can the addition overflow? Is the addition even right? This function is used in .apply() where it's
> > usually right to round down.
> 
> No, It won't overflow. The logic is proposed by you in v17 for DIV64_U64_ROUND_UP and it is
> passing all tests with PWM_DEBUG=y.

Then believe my former self, I didn't redo all the maths in this cycle.

> > > +	pm_runtime_enable(&pdev->dev);
> > > +	ret = pm_runtime_resume_and_get(&pdev->dev);
> > > +	if (ret)
> > > +		goto err_reset;
> > > +
> > > +	ret = clk_rate_exclusive_get(rzg2l_gpt->clk);
> > 
> > There is a devm variant of this function in the mean time.
> 
> OK, currently for testing I picked it from next.

For the next submission round make sure to properly use the --base
parameter to not annoy the build bots. Or feel free to base your patch
on next.

Best regards
Uwe

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

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