linux-kernel - Re: [PATCH v1 1/5] ARM: trusted_foundations: Implement L2 cache initialization callback

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Date:   Sun, 20 May 2018 17:53:11 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Russell King - ARM Linux <linux@...linux.org.uk>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        linux-tegra@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Peter Geis <pgwipeout@...il.com>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>
Subject: Re: [PATCH v1 1/5] ARM: trusted_foundations: Implement L2 cache
 initialization callback

On 20.05.2018 17:08, Russell King - ARM Linux wrote:
> On Sun, May 20, 2018 at 01:15:38PM +0300, Dmitry Osipenko wrote:
>> Implement L2 cache initialization firmware callback that should be invoked
>> early in boot to enable cache HW.
>>
>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>> ---
>>  arch/arm/firmware/trusted_foundations.c | 23 +++++++++++++++++++++++
>>  1 file changed, 23 insertions(+)
>>
>> diff --git a/arch/arm/firmware/trusted_foundations.c b/arch/arm/firmware/trusted_foundations.c
>> index 3fb1b5a1dce9..198ce5c75ca0 100644
>> --- a/arch/arm/firmware/trusted_foundations.c
>> +++ b/arch/arm/firmware/trusted_foundations.c
>> @@ -18,8 +18,13 @@
>>  #include <linux/init.h>
>>  #include <linux/of.h>
>>  #include <asm/firmware.h>
>> +#include <asm/outercache.h>
>>  #include <asm/trusted_foundations.h>
>>  
>> +#define TF_CACHE_MAINT		0xfffff100
>> +
>> +#define TF_CACHE_INIT		1
>> +
>>  #define TF_SET_CPU_BOOT_ADDR_SMC 0xfffff200
>>  
>>  #define TF_CPU_PM		0xfffffffc
>> @@ -63,9 +68,27 @@ static int tf_prepare_idle(void)
>>  	return 0;
>>  }
>>  
>> +#ifdef CONFIG_CACHE_L2X0
>> +static void tf_cache_write_sec(unsigned long val, unsigned int reg)
>> +{
>> +	pr_warn("%s: Ignoring write [0x%x]: 0x%08lx\n", __func__, reg, val);
> 
> Why at warning level?  Is this some issue that the user needs to be
> warned about?
> 

If cache-l2x0 code will be changed in the future in a way that it will try to do
something using the secure-registers, then user should be informed about that
incident as we are ignoring the accesses to secure-registers and this may lead
to an undesired consequences. If a such change in cache-l2x0 will happen, then
we will have to take some action by either fixing the invalid accesses or
silencing the warning message if will be appropriate. For now I'd prefer to have
verbosity in the KMSG to masking the potential problems.