Re: [PATCH] AM35xx: disable checking for reserved feature bits

[Kevin Hilman <khilman@ti.com>]

"Hiremath, Vaibhav" <hvaibhav@ti.com> writes:

>> -----Original Message-----
>> From: Hilman, Kevin
>> Sent: Saturday, December 10, 2011 6:51 AM
>> To: Tony Lindgren
>> Cc: Ilya Yanok; linux-omap@vger.kernel.org; wd@denx.de; dzu@denx.de;
>> sasha_d@emcraft.com; Hiremath, Vaibhav
>> Subject: Re: [PATCH] AM35xx: disable checking for reserved feature bits
>> 
>> Tony Lindgren <tony@atomide.com> writes:
>> 
>> [...]
>> 
>> >> This "feature" selection mechanism is clearly not scaling to newer SoCs.
>> >> While this patch works around the problem, IMO, we need a more scalable
>> >> solution.
>> >
>> > Agreed.
>> >
> <snip>
>> >
>> > This should be coordinated with the splitting of feature detection
>> > as posted by Vaibhave in thread "[RFC PATCH] arm:omap: cleanup & split
>> > omap2/3/4_check_revision function" thread.
>> 
>> Vaibhav,
>> 
>> Feel free to take my proposed patch and develop it further and include
>> it in your rework of the SoC/feature detection.
>> 
> Kevin,
>
> I spend some time on this, and I think it is not possible to use HWMOD 
> Entries for feature check. Reason being,
>
> 	- The whole revision story is built upon howkeye and silicon rev.
>         And both remains same for different devices in same family, 
>         For example,
>           omap3430, omap3503 and omap3515 (for that matter all AM37x) all
>           will have same howkeye and silicon revision no.

I see now.

>         Also, in the kernel we have something like.
>
> # define cpu_is_omap3515()              (cpu_is_omap3430() &&           \
>                                                  (!omap3_has_iva()) &&   \
>                                                  (omap3_has_sgx()))
> # define cpu_is_omap3525()              (cpu_is_omap3430() &&           \
>                                                  (!omap3_has_sgx()) &&   \
>                                                  (omap3_has_iva()))
>
>         Which means, you can not do IP detection before check_feature
>         function.
> 	- The current omap_hwmod_xxxx_data.c uses silicon version alone
>         and only differentiate between silicon versions. We do not 
>         differentiate between different family of devices while registering
>         hwmod data.
>
> So the conclusion is, we have to stick to check_feature function.

I don't fully agree.

I still think we need to rework how we're using cpu_is_* checks.

Specifially, we need to start separating the checking for SoC family
(based on die ID) and specific IP blocks.

I spent some time on this today and just posted a series for RFC to
hopefully move in that direction.   Let me know what you think.

Kevin