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Message-ID: <AM6PR04MB4966C6D0E08AB4C25B280CF480689@AM6PR04MB4966.eurprd04.prod.outlook.com>
Date: Fri, 19 Mar 2021 03:31:39 +0000
From: Aisheng Dong <aisheng.dong@....com>
To: Ulf Hansson <ulf.hansson@...aro.org>,
Shawn Guo <shawnguo@...nel.org>,
Sascha Hauer <s.hauer@...gutronix.de>
CC: Ying Liu <victor.liu@....com>, Peng Fan <peng.fan@....com>,
dl-linux-imx <linux-imx@....com>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] firmware: imx: scu-pd: Update comments for single global
power domain
Hi Ulf,
> From: Ulf Hansson <ulf.hansson@...aro.org>
> Sent: Wednesday, March 17, 2021 5:31 PM
>
> Since the introduction of the PM domain support for the scu-pd, the genpd
> framework has been continuously improved. More preciously, using a single
> global power domain can quite easily be deployed for imx platforms.
>
> To avoid confusions, let's therefore make an update to the comments about
> the missing pieces.
>
> Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
Thanks for the update.
Reviewed-by: Dong Aisheng <aisheng.dong@....com>
BTW, I'm still uncertain if the new approach can finally work well for i.MX as SCU PD
also supports multiple low power state.
I could investigate it more when I adding multi low power states support.
Regards
Aisheng
> ---
> drivers/firmware/imx/scu-pd.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/firmware/imx/scu-pd.c b/drivers/firmware/imx/scu-pd.c
> index 08533ee67626..6e178a63442d 100644
> --- a/drivers/firmware/imx/scu-pd.c
> +++ b/drivers/firmware/imx/scu-pd.c
> @@ -29,6 +29,10 @@
> * The framework needs some proper extension to support multi power
> * domain cases.
> *
> + * Update: Genpd assigns the ->of_node for the virtual device before it
> + * invokes ->attach_dev() callback, hence parsing for device resources via
> + * DT should work fine.
> + *
> * 2. It also breaks most of current drivers as the driver probe sequence
> * behavior changed if removing ->power_on|off() callback and use
> * ->start() and ->stop() instead. genpd_dev_pm_attach will only power
> @@ -39,8 +43,11 @@
> * domain enabled will trigger a HW access error. That means we need fix
> * most drivers probe sequence with proper runtime pm.
> *
> - * In summary, we need fix above two issue before being able to switch to
> - * the "single global power domain" way.
> + * Update: Runtime PM support isn't necessary. Instead, this can easily be
> + * fixed in drivers by adding a call to dev_pm_domain_start() during
> probe.
> + *
> + * In summary, the second part needs to be addressed via minor updates
> + to the
> + * relevant drivers, before the "single global power domain" model can be
> used.
> *
> */
>
> --
> 2.25.1
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