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

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Message-ID: <56CC490F.3040301@ti.com>
Date:	Tue, 23 Feb 2016 17:27:03 +0530
From:	Kishon Vijay Abraham I <kishon@...com>
To:	Paul Walmsley <paul@...an.com>
CC:	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

Hi Paul,

On Monday 22 February 2016 03:25 PM, Kishon Vijay Abraham I wrote:
> Hi Paul,
> 
> On Monday 22 February 2016 12:01 PM, Paul Walmsley wrote:
>> Kishon,
>>
>> On Mon, 22 Feb 2016, Kishon Vijay Abraham I wrote:
>>
>>> Sekhar,
>>>
>>> On Thursday 18 February 2016 07:51 PM, Sekhar Nori wrote:
>>>> On Friday 12 February 2016 10:50 PM, Suman Anna wrote:
>>>>> Sekhar,
>>>>> Will you be following up with above suggestion since Kishon is gonna be out?
>>>>
>>>> Alright, noticed this action for me :) Went through the thread, and 
>>>> looks like this is what we want to see?
>>>>
>>>> Thanks,
>>>> Sekhar
>>>>
>>>> ---8<---
>>>> From e3ba368f2235e1bf38a22ba8ea4e5c12aaafda19 Mon Sep 17 00:00:00 2001
>>>> Message-Id: <e3ba368f2235e1bf38a22ba8ea4e5c12aaafda19.1455803758.git.nsekhar@...com>
>>>> From: Sekhar Nori <nsekhar@...com>
>>>> Date: Thu, 18 Feb 2016 16:49:56 +0530
>>>> Subject: [PATCH 1/1] 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>
>>>> ---
>>>> Applies to tag for-v4.6/omap-hwmod-a of Paul W's tree.
>>>>
>>>>  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,
>>>>  };
>>>
>>> Thanks for the patch.
>>
>> Could you please test the bind/unbind functionality just to make sure it 
>> works?
> 
> The pci-dra7xx driver neither expose the bind/unbind sysfs entry nor can be
> built as module.
> 
> However I hacked the pci-dra7xx driver to be built as module [and reverted
> Commit 5de85b9d57ab ("PM / runtime: Re-init runtime PM states at probe error
> and driver unbind")] and I don't see an abort when the PCI registers are
> accessed after rmmod/modprobe cycle (that was the issue that Sekhar's patch
> tried to solve). However PCI as such doesn't work after rmmod/modprobe cycle
> [1], but this is a different issue most likely in PCIe core and has to debugged.
> 
> In summary, there are other issues in PCI across rmmod/modprobe cycle but the
> reset of pci-dra7xx happens fine with this patch.

Do you expect any other testing from me?

-Kishon

> 
> Thanks
> Kishon
> 
> [1] -> http://pastebin.ubuntu.com/15169387/
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