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

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Date:	Mon, 22 Feb 2016 11:48:21 +0530
From:	Kishon Vijay Abraham I <kishon@...com>
To:	Sekhar Nori <nsekhar@...com>, Suman Anna <s-anna@...com>,
	Paul Walmsley <paul@...an.com>, <d-gerlach@...com>
CC:	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

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.

-Kishon