From mboxrd@z Thu Jan  1 00:00:00 1970
From: Khiem Nguyen <khiem.nguyen.xt@renesas.com>
Date: Tue, 07 Oct 2014 04:17:44 +0000
Subject: Re: [PATCH] ARM: shmobile: Handle CA7 arch timer delay
Message-Id: <54336968.3090304@renesas.com>
List-Id: <linux-sh.vger.kernel.org>
References: <20141005235920.3532.40364.sendpatchset@w520>
In-Reply-To: <20141005235920.3532.40364.sendpatchset@w520>
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To: linux-sh@vger.kernel.org

Hi Magnus-san,

On 10/7/2014 12:32 PM, Magnus Damm wrote:
> Hi Khiem-san,
> 
> On Tue, Oct 7, 2014 at 9:50 AM, Khiem Nguyen
> <khiem.nguyen.xt@renesas.com> wrote:
>> Hi Magnus-san,
>>
>>
>>
>> Thanks for your patch.
> 
> Thanks for your email.
> 
>> I have 2 points to confirm.
>>
>> Please kindly share your opinions.
> 
> Sure.
> 
>> On 10/6/2014 8:59 AM, Magnus Damm wrote:
>>> From: Magnus Damm <damm+renesas@opensource.se>
>>>
>>> Update the delay code to include arch timer checks
>>> for CA7. From a arch timer availability perspective
>>> CA7 should be treated same as CA15.
>>
>>> Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
>>> ---
>>>
>>>  Written against renesas-devel-20141002-v3.17-rc7
>>>
>>>  arch/arm/mach-shmobile/timer.c |   23 +++++++++++++++--------
>>>  1 file changed, 15 insertions(+), 8 deletions(-)
>>>
>>> --- 0001/arch/arm/mach-shmobile/timer.c
>>> +++ work/arch/arm/mach-shmobile/timer.c       2014-10-06 08:44:21.000000000 +0900
>>> @@ -45,6 +45,7 @@ void __init shmobile_init_delay(void)
>>>       struct device_node *np, *cpus;
>>>       bool is_a7_a8_a9 = false;
>>>       bool is_a15 = false;
>>> +     bool has_arch_timer = false;
>>>       u32 max_freq = 0;
>>>
>>>       cpus = of_find_node_by_path("/cpus");
>>> @@ -57,12 +58,16 @@ void __init shmobile_init_delay(void)
>>>               if (!of_property_read_u32(np, "clock-frequency", &freq))
>>>                       max_freq = max(max_freq, freq);
>>>
>>> -             if (of_device_is_compatible(np, "arm,cortex-a7") ||
>>> -                 of_device_is_compatible(np, "arm,cortex-a8") ||
>>> -                 of_device_is_compatible(np, "arm,cortex-a9"))
>>> +             if (of_device_is_compatible(np, "arm,cortex-a8") ||
>>> +                 of_device_is_compatible(np, "arm,cortex-a9")) {
>>>                       is_a7_a8_a9 = true;
>>> -             else if (of_device_is_compatible(np, "arm,cortex-a15"))
>>> +             } else if (of_device_is_compatible(np, "arm,cortex-a7")) {
>>> +                     is_a7_a8_a9 = true;
>>> +                     has_arch_timer = true;
>>> +             } else if (of_device_is_compatible(np, "arm,cortex-a15")) {
>>>                       is_a15 = true;
>>> +                     has_arch_timer = true;
>>
>> Because has_arch_timer set true here, below delay setting for a15 will never be entered.
>> However, before this patch, it will be executed in case CONFIG_ARM_ARCH_TIMER is disable.
>> Is it your intention ?
> 
> No, it is not my intention. "has_arch_timer" here is used to tell if
> the arch timer hardware may be available. This only happens on CA7 and
> CA15.
> 
>>> +             }
>>>       }
>>>
>>>       of_node_put(cpus);
>>> @@ -70,10 +75,12 @@ void __init shmobile_init_delay(void)
>>>       if (!max_freq)
>>>               return;
>>>
>>> -     if (is_a7_a8_a9)
>>> -             shmobile_setup_delay_hz(max_freq, 1, 3);
>>> -     else if (is_a15 && !IS_ENABLED(CONFIG_ARM_ARCH_TIMER))
>>> -             shmobile_setup_delay_hz(max_freq, 2, 4);
>>> +     if (!has_arch_timer || !IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) {
>>
>> Above condition checking will apply to all cortex cores, including a8 and a9.
>> However, before this patch, delay setting will be set for a8 and a9,
>> regardless of CONFIG_ARM_ARCH_TIMER.
>> Is it your intention ?
> 
> My intention is to only call shmobile_setup_delay_hz() in the following cases:
> 
> A) arch timer hardware is unavailable (has_arch_timer is false)
> or
> B) arch timer is available (has_arch_timer is true) and
> CONFIG_ARM_ARCH_TIMER is disabled.
> 
> Case A) above covers CPU cores without arch timer, like CA8 and CA9.
> 
> Is there any problem?

Your implementation is OK.
At the beginning, I confused the meaning of using 'has_arch_timer'
and CONFIG_ARM_ARCH_TIMER.
Now, I understood the implementation via your explanation.

> Cheers,
> 
> / magnus
> 

-- 
Best regards,
KHIEM Nguyen