linux-kernel - Re: [PATCH v10 18/21] ARM64 / ACPI: Select ACPI_REDUCED_HARDWARE

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Message-ID: <18318670.U16Joq6nSS@vostro.rjw.lan>
Date:	Wed, 18 Mar 2015 16:06:35 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Hanjun Guo <hanjun.guo@...aro.org>
Cc:	"guohanjun@...wei.com" <guohanjun@...wei.com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	Olof Johansson <olof@...om.net>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	Mark Rutland <Mark.Rutland@....com>,
	"graeme.gregory@...aro.org" <graeme.gregory@...aro.org>,
	Sudeep Holla <Sudeep.Holla@....com>,
	"jcm@...hat.com" <jcm@...hat.com>,
	Marc Zyngier <Marc.Zyngier@....com>,
	Mark Brown <broonie@...nel.org>,
	Robert Richter <rric@...nel.org>,
	Timur Tabi <timur@...eaurora.org>,
	Ashwin Chaugule <ashwinc@...eaurora.org>,
	"suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>,
	Al Stone <al.stone@...aro.org>
Subject: Re: [PATCH v10 18/21] ARM64 / ACPI: Select ACPI_REDUCED_HARDWARE_ONLY if ACPI is enabled on ARM64

On Wednesday, March 18, 2015 09:18:20 AM Lorenzo Pieralisi wrote:
> On Mon, Mar 16, 2015 at 11:33:29AM +0000, Hanjun Guo wrote:
> > On 2015年03月13日 19:04, Lorenzo Pieralisi wrote:
> > > On Fri, Mar 13, 2015 at 03:28:45AM +0000, Hanjun Guo wrote:
> > >
> > > [...]
> > >
> > >>>   /*
> > >>>    * acpi_boot_table_init() called from setup_arch(), always.
> > >>>    *	1. find RSDP and get its address, and then find XSDT
> > >>>    *	2. extract all tables and checksums them all
> > >>>    *	3. check ACPI FADT revision
> > >>> + *	4. check ACPI FADT HW reduced flag
> > >>>    *
> > >>>    * We can parse ACPI boot-time tables such as MADT after
> > >>>    * this function is called.
> > >>>    */
> > >>>   void __init acpi_boot_table_init(void)
> > >>>   {
> > >>> +	struct acpi_table_header *table;
> > >>> +	struct acpi_table_fadt *fadt;
> > >>> +	acpi_status status;
> > >>> +	acpi_size tbl_size;
> > >>> +
> > >>>   	/*
> > >>>   	 * Enable ACPI instead of device tree unless
> > >>>   	 * - ACPI has been disabled explicitly (acpi=off), or
> > >>> @@ -351,19 +318,52 @@ void __init acpi_boot_table_init(void)
> > >>>   	    (!param_acpi_force && of_scan_flat_dt(dt_scan_depth1_nodes, NULL)))
> > >>>   		return;
> > >>>
> > >>> -	enable_acpi();
> > >>> -
> > >>>   	/* Initialize the ACPI boot-time table parser. */
> > >>>   	if (acpi_table_init()) {
> > >>
> > >> Since we disable ACPI in default, it is a bit strange for me to init all
> > >> the ACPI tables and parse FADT when ACPI is disabled, could you
> > >> put some comments here to clarify the purpose? other than that, it is looks
> > >> good to me.
> > >
> > > Ok, the purpose was to make things simpler, but I think that given
> > > current code it is not 100% safe to init ACPI tables with
> > > acpi_disabled == 1.
> > >
> > > To me having to enable ACPI to parse the tables and check *if* ACPI tables
> > > are there is a bit crazy, but I agree with you that given current code
> > > it is safer.
> > >
> > > Patch rewritten, here below, please have a look, test it and rework
> > > bits as needed, I added comments where I thought they were needed but
> > > please add to that if you feel it is worth it.
> > >
> > > It should be easy to split, let me know if you want an incremental
> > > version.
> > 
> > This one is much better, pretty fine to me, thanks!
> > 
> > I assume that this patch is cleanup patch on top of ARM64 ACPI
> > core patches, right?
> 
> For the records, I created a branch with my patch split over some
> of your patches, even though I think to make things simpler it is best
> to apply it as a single patch on top of your series,

I agree.  In particular, the patches that have already been reviewed and
ACKed won't need to be reviewed again this way which seems to be crucially
important to me.

> I will prepare the commit log for the single patch version too.

Thanks!

Hanjun, please add this one to the series when ready.


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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