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

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Message-ID: <20160301144335.GA11916@localhost>
Date:	Tue, 1 Mar 2016 08:43:36 -0600
From:	Bjorn Helgaas <helgaas@...nel.org>
To:	Kishon Vijay Abraham I <kishon@...com>
Cc:	Paul Walmsley <paul@...an.com>, Sekhar Nori <nsekhar@...com>,
	Suman Anna <s-anna@...com>, d-gerlach@...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
Subject: Re: [PATCH v3 3/3] pci: dra7xx: use pdata callbacks to perform reset

On Tue, Mar 01, 2016 at 05:25:56PM +0530, Kishon Vijay Abraham I wrote:
> Hi,
> 
> On Tuesday 01 March 2016 01:55 PM, Paul Walmsley wrote:
> > 
> > Folks, the following is what I've queued for this.
> 
> Thanks Paul.
> 
> Bjorn,
> 
> With this patch merged, enabling pci-dra7xx won't result in system freeze
> anymore. I can send a patch to revert depends on BROKEN.

Great!  Please send me that patch, and I'll merge it for v4.6.

> > From: Sekhar Nori <nsekhar@...com>
> > Date: Thu, 18 Feb 2016 16:49:56 +0530
> > Subject: [PATCH] ARM: DRA7: hwmod: Add custom reset handler for PCIeSS
> > 
> > Add a custom reset handler for DRA7x PCIeSS. This
> > handler is required to deassert PCIe hardreset lines
> > after they have been asserted.
> > 
> > This enables the PCIe driver to access registers after
> > PCIeSS has been runtime enabled without having to
> > deassert hardreset lines itself.
> > 
> > With this patch applied, used lspci to make sure
> > connected PCIe device enumerates on DRA74x and DRA72x
> > EVMs.
> > 
> > Signed-off-by: Sekhar Nori <nsekhar@...com>
> > Reported-by: Richard Cochran <richardcochran@...il.com>
> > Tested-by: Kishon Vijay Abraham I <kishon@...com>
> > Cc: Suman Anna <s-anna@...com>
> > Cc: Dave Gerlach <d-gerlach@...com>
> > Cc: Tony Lindgren <tony@...mide.com>
> > Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> > Cc: Russell King <linux@....linux.org.uk>
> > Signed-off-by: Paul Walmsley <paul@...an.com>
> > ---
> >  arch/arm/mach-omap2/omap_hwmod_7xx_data.c | 23 +++++++++++++++++++++++
> >  1 file changed, 23 insertions(+)
> > 
> > diff --git a/arch/arm/mach-omap2/omap_hwmod_7xx_data.c b/arch/arm/mach-omap2/omap_hwmod_7xx_data.c
> > index b61355e2a771..252b74633e31 100644
> > --- a/arch/arm/mach-omap2/omap_hwmod_7xx_data.c
> > +++ b/arch/arm/mach-omap2/omap_hwmod_7xx_data.c
> > @@ -1526,8 +1526,31 @@ static struct omap_hwmod dra7xx_ocp2scp3_hwmod = {
> >   *
> >   */
> >  
> > +/*
> > + * As noted in documentation for _reset() in omap_hwmod.c, the stock reset
> > + * functionality of OMAP HWMOD layer does not deassert the hardreset lines
> > + * associated with an IP automatically leaving the driver to handle that
> > + * by itself. This does not work for PCIeSS which needs the reset lines
> > + * deasserted for the driver to start accessing registers.
> > + *
> > + * We use a PCIeSS HWMOD class specific reset handler to deassert the hardreset
> > + * lines after asserting them.
> > + */
> > +static int dra7xx_pciess_reset(struct omap_hwmod *oh)
> > +{
> > +	int i;
> > +
> > +	for (i = 0; i < oh->rst_lines_cnt; i++) {
> > +		omap_hwmod_assert_hardreset(oh, oh->rst_lines[i].name);
> > +		omap_hwmod_deassert_hardreset(oh, oh->rst_lines[i].name);
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> >  static struct omap_hwmod_class dra7xx_pciess_hwmod_class = {
> >  	.name	= "pcie",
> > +	.reset	= dra7xx_pciess_reset,
> >  };
> >  
> >  /* pcie1 */
> >