linux-kernel - Re: [PATCH] ARM: OMAP2+: hwmod: Fix _wait_target

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Date:	Mon, 5 Jan 2015 14:05:32 +0530
From:	Lokesh Vutla <lokeshvutla@...com>
To:	Paul Walmsley <paul@...an.com>, Roger Quadros <rogerq@...com>
CC:	<tony@...mide.com>, <t-kristo@...com>, <nm@...com>,
	<nsekhar@...com>, <bcousson@...libre.com>,
	<linux-omap@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <s-anna@...com>
Subject: Re: [PATCH] ARM: OMAP2+: hwmod: Fix _wait_target_ready() for hwmods
 without sysc

Hi Paul,
On Saturday 03 January 2015 02:40 AM, Paul Walmsley wrote:
> + Suman, lakml
> 
> Hi Roger
> 
> On Thu, 18 Dec 2014, Roger Quadros wrote:
> 
>> Fixing up Paul's email id.
>>
>> cheers,
>> -roger
>>
>> On 18/12/14 17:49, Roger Quadros wrote:
>>> There are quite a few hwmods that don't have sysconfig register and so
>>> _find_mpu_rt_port(oh) will return NULL thus preventing ready state check
>>> on those modules after the module is enabled.
> 
> Hmm.  Any IP block that exposes registers that are accessible by the MPU 
> should have an MPU register target port, even if there's no SYSCONFIG 
> register.  And if an IP block doesn't have registers that are accessible 
> from the MPU, then there shouldn't be much point to waiting for the module 
> to become ready.
> 
> Looks like the real problem is the test for oh->class->sysc before the 
> call to _init_mpu_rt_base().  That was introduced by commit 6423d6df1440 
> ("ARM: OMAP2+: hwmod: check for module address space during init"). It's 
> not clear to me why that test was added, since _init_mpu_rt_base() doesn't 
> do anything with oh->class->sysc or SYSCONFIG registers.
This was introduced by commit 
97597b962529 (ARM: OMAP2+: hwmod: Don't call _init_mpu_rt_base if no sysc)
Patch description states that "there are few hwmod which doesn't have sysconfig registers and hence
no need to ioremap() them in early init code".
Isn't this correct? 
May be a dumb question: If IP doesn't have sysconfig, is there any case that hwmod does
access the register address space of that IP? Why do we need to enable MPU register target port?

Thanks and regards,
Lokesh

> 
> Could you please test the following patch?
> I don't have an AM437x-gp-evm.  
> 
> 
> - Paul
> 
> ---
>  arch/arm/mach-omap2/omap_hwmod.c | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/arm/mach-omap2/omap_hwmod.c b/arch/arm/mach-omap2/omap_hwmod.c
> index cbb908dc5cf0..ce6d11f3eda7 100644
> --- a/arch/arm/mach-omap2/omap_hwmod.c
> +++ b/arch/arm/mach-omap2/omap_hwmod.c
> @@ -2451,14 +2451,10 @@ static int __init _init(struct omap_hwmod *oh, void *data)
>  				oh->name, np->name);
>  	}
>  
> -	if (oh->class->sysc) {
> -		r = _init_mpu_rt_base(oh, NULL, index, np);
> -		if (r < 0) {
> -			WARN(1, "omap_hwmod: %s: doesn't have mpu register target base\n",
> -			     oh->name);
> -			return 0;
> -		}
> -	}
> +	r = _init_mpu_rt_base(oh, NULL, index, np);
> +	if (r < 0)
> +		pr_debug("omap_hwmod: %s: doesn't have mpu register target base\n",
> +			 oh->name);
>  
>  	r = _init_clocks(oh, NULL);
>  	if (r < 0) {
> 

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