linux-kernel - Re: [PATCH v3 3/3] pci: dra7xx: use pdata callbacks to perform reset

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Message-ID: <alpine.DEB.2.02.1602090846480.2906@utopia.booyaka.com>
Date:	Tue, 9 Feb 2016 08:49:13 +0000 (UTC)
From:	Paul Walmsley <paul@...an.com>
To:	Suman Anna <s-anna@...com>
cc:	Kishon Vijay Abraham I <kishon@...com>,
	Tony Lindgren <tony@...mide.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, richardcochran@...il.com,
	Russell King <linux@....linux.org.uk>,
	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, nsekhar@...com
Subject: Re: [PATCH v3 3/3] pci: dra7xx: use pdata callbacks to perform
 reset

On Mon, 8 Feb 2016, Suman Anna wrote:

> On 02/07/2016 08:48 PM, Paul Walmsley wrote:
> > On Tue, 2 Feb 2016, Kishon Vijay Abraham I wrote:
> > 
> >> Paul, what do you think is the best way forward to perform reset?
> > 
> > Many of the IP blocks with PRM hardreset lines are processor IP blocks. 
> > Those often need special reset handling to ensure that WFI/HLT-like 
> > instructions are executed after reset.  This special handling ensures that 
> > the IP blocks' bus initiator interfaces indicate that they are in standby 
> > to the PRCM - thus allowing power management for the rest of the chip to 
> > work correctly.
> > 
> > But that doesn't seem to be the case with PCIe - and maybe others - 
> > possibly some of the MMUs?  
> 
> Yeah, the sequencing between clocks and resets would still be the same
> for MMUs, so, adding the custom flags for MMUs is fine.

I'm curious as to whether HWMOD_CUSTOM_HARDRESET is needed for the MMUs.  
We've stated that the main point of the custom hardreset code is to handle 
processors that need to be placed into WFI/HLT, but it doesn't seem like 
there would be an equivalent for MMUs.  Thoughts?


- Paul