linux-kernel - RE: [PATCH] pmdomain: imx: Fix i.MX8MP VPU

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Message-ID:
 <PAXPR04MB845908F512331CBDA0890D678866A@PAXPR04MB8459.eurprd04.prod.outlook.com>
Date: Fri, 6 Feb 2026 01:46:52 +0000
From: Peng Fan <peng.fan@....com>
To: Frank Li <frank.li@....com>, "Peng Fan (OSS)" <peng.fan@....nxp.com>
CC: Ulf Hansson <ulf.hansson@...aro.org>, Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>, Pengutronix Kernel Team
	<kernel@...gutronix.de>, Fabio Estevam <festevam@...il.com>, Lucas Stach
	<l.stach@...gutronix.de>, Jacky Bai <ping.bai@....com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>, "imx@...ts.linux.dev"
	<imx@...ts.linux.dev>, "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "stable@...r.kernel.org"
	<stable@...r.kernel.org>
Subject: RE: [PATCH] pmdomain: imx: Fix i.MX8MP VPU_H1 power up sequence

> Subject: Re: [PATCH] pmdomain: imx: Fix i.MX8MP VPU_H1 power up
> sequence
> 
> On Wed, Jan 28, 2026 at 11:11:25PM +0800, Peng Fan (OSS) wrote:
> > From: Peng Fan <peng.fan@....com>
> >
> 
> > +
> > +	if (action == GENPD_NOTIFY_ON) {
> > +		/*
> > +		 * On power up we have no software backchannel to
> the GPC to
> > +		 * wait for the ADB handshake to happen, so we just
> delay for a
> > +		 * bit. On power down the GPC driver waits for the
> handshake.
> > +		 */
> > +
> > +		udelay(5);
> 
> this time quite short, suggest read register before udelay() because
> udelay() is not neccesary to have MMIO read/write.

Missed this comment.
This is to wait ADB handshake, not waiting value to be written
into registers(saying use readl).

5us is enough for ADB handshake, I prefer to keep it.

Thanks,
Peng.

> 
> Frank
> > +
> > +		/* set "fuse" bits to enable the VPUs */
> > +		regmap_set_bits(bc->regmap, 0x8, 0xffffffff);
> > +		regmap_set_bits(bc->regmap, 0xc, 0xffffffff);
> > +		regmap_set_bits(bc->regmap, 0x10, 0xffffffff);
> > +		regmap_set_bits(bc->regmap, 0x14, 0xffffffff);
> > +	}
> > +
> > +	return NOTIFY_OK;
> > +}
> > +
> >  static const struct imx8m_blk_ctrl_data
> imx8mp_vpu_blk_ctl_dev_data = {
> >  	.max_reg = 0x18,
> > -	.power_notifier_fn = imx8mm_vpu_power_notifier,
> > +	.power_notifier_fn = imx8mp_vpu_power_notifier,
> >  	.domains = imx8mp_vpu_blk_ctl_domain_data,
> >  	.num_domains =
> ARRAY_SIZE(imx8mp_vpu_blk_ctl_domain_data),
> >  };
> >
> > ---
> > base-commit: 4f938c7d3b25d87b356af4106c2682caf8c835a2
> > change-id: 20260128-imx8mp-vc8000e-pm-4278e6d48b54
> >
> > Best regards,
> > --
> > Peng Fan <peng.fan@....com>
> >