On 9/23/2019 7:57 AM, Marc Zyngier wrote:
> On 23/09/2019 15:39, Florian Fainelli wrote:
>>
>>
>> On 9/23/2019 1:52 AM, Marc Zyngier wrote:
>>> On 22/09/2019 20:08, Florian Fainelli wrote:
>>>>
>>>>
>>>> On 9/22/2019 5:38 AM, Marc Zyngier wrote:
>>>>> On Fri, 13 Sep 2019 12:15:42 -0700
>>>>> Florian Fainelli <f.faine...@gmail.com> wrote:
>>>>>
>>>>>> On some specific chips like 7211 we need to leave some interrupts
>>>>>> untouched/forwarded to the VPU which is another agent in the system
>>>>>> making use of that interrupt controller hardware (goes to both ARM GIC
>>>>>> and VPU L1 interrupt controller). Make that possible by using the
>>>>>> existing brcm,int-fwd-mask property.
>>>>>>
>>>>>> Signed-off-by: Florian Fainelli <f.faine...@gmail.com>
>>>>>> ---
>>>>>> drivers/irqchip/irq-bcm7038-l1.c | 15 +++++++++++++--
>>>>>> 1 file changed, 13 insertions(+), 2 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/irqchip/irq-bcm7038-l1.c
>>>>>> b/drivers/irqchip/irq-bcm7038-l1.c
>>>>>> index 0673a44bbdc2..811a34201dd4 100644
>>>>>> --- a/drivers/irqchip/irq-bcm7038-l1.c
>>>>>> +++ b/drivers/irqchip/irq-bcm7038-l1.c
>>>>>> @@ -44,6 +44,7 @@ struct bcm7038_l1_chip {
>>>>>> struct list_head list;
>>>>>> u32 wake_mask[MAX_WORDS];
>>>>>> #endif
>>>>>> + u32 irq_fwd_mask[MAX_WORDS];
>>>>>> u8 affinity[MAX_WORDS * IRQS_PER_WORD];
>>>>>> };
>>>>>>
>>>>>> @@ -265,6 +266,7 @@ static int __init bcm7038_l1_init_one(struct
>>>>>> device_node *dn,
>>>>>> resource_size_t sz;
>>>>>> struct bcm7038_l1_cpu *cpu;
>>>>>> unsigned int i, n_words, parent_irq;
>>>>>> + int ret;
>>>>>>
>>>>>> if (of_address_to_resource(dn, idx, &res))
>>>>>> return -EINVAL;
>>>>>> @@ -278,6 +280,14 @@ static int __init bcm7038_l1_init_one(struct
>>>>>> device_node *dn,
>>>>>> else if (intc->n_words != n_words)
>>>>>> return -EINVAL;
>>>>>>
>>>>>> + ret = of_property_read_u32_array(dn , "brcm,int-fwd-mask",
>>>>>
>>>>> What is the exact meaning of "fwd"? Forward? FirmWare Dementia?
>>>>
>>>> Here it is meant to be "forward", we have defined this property name
>>>> before for irq-bcm7120-l2.c and felt like reusing the same name to avoid
>>>> multiplying properties would be appropriate, see patch #4. If you prefer
>>>> something named brcm,firmware-configured-mask, let me know.
>>>
>>> It's just a name, but I found it a bit confusing. Bah, never mind.
>>>
>>>>>
>>>>>> + intc->irq_fwd_mask, n_words);
>>>>>> + if (ret != 0 && ret != -EINVAL) {
>>>>>> + /* property exists but has the wrong number of words */
>>>>>> + pr_err("invalid brcm,int-fwd-mask property\n");
>>>>>> + return -EINVAL;
>>>>>> + }
>>>>>> +
>>>>>> cpu = intc->cpus[idx] = kzalloc(sizeof(*cpu) + n_words *
>>>>>> sizeof(u32),
>>>>>> GFP_KERNEL);
>>>>>> if (!cpu)
>>>>>> @@ -288,8 +298,9 @@ static int __init bcm7038_l1_init_one(struct
>>>>>> device_node *dn,
>>>>>> return -ENOMEM;
>>>>>>
>>>>>> for (i = 0; i < n_words; i++) {
>>>>>> - l1_writel(0xffffffff, cpu->map_base +
>>>>>> reg_mask_set(intc, i));
>>>>>> - cpu->mask_cache[i] = 0xffffffff;
>>>>>> + l1_writel(0xffffffff & ~intc->irq_fwd_mask[i],
>>>>>> + cpu->map_base + reg_mask_set(intc, i));
>>>>>> + cpu->mask_cache[i] = 0xffffffff &
>>>>>> ~intc->irq_fwd_mask[i];
>>>>>
>>>>> I seem to remember that (0xffffffff & whatever) == whatever, as long as
>>>>> 'whatever' is a 32bit quantity. So what it this for?
>>>>
>>>> It is 0xffff_ffff & ~whatever here.
>>>
>>> Which doesn't change anything.
>>>
>>>> In the absence of this property
>>>> being specified, the data is all zeroed out, so we would have
>>>> 0xffff_ffff & 0xffff_ffff which is 0xffff_ffff. If this property is
>>>> specified, we would have one more or bits set, and it would be e.g.:
>>>> 0x100 so we would have 0xffff_ffff & ~(0x100) = 0xffff_feff which is
>>>> what we would want here to preserve whatever the firmware has already
>>>> configured.
>>>
>>> OK, I must be stupid:
>>>
>>> #include <stdio.h>
>>>
>>> int main(int argc, char *argv[])
>>> {
>>> unsigned int v = 0x100;
>>> printf ("%x\n", ~v);
>>> }
>>> maz@filthy-habit$ ./x
>>> fffffeff
>>>
>>> You might as well OR it with zeroes, if you want.
>>
>> Not sure I understand your point here.
>>
>> We used to write 0xffff_ffff to both the hardware and the mask cache to
>> have all interrupts masked by default. Now we want to have some bits
>> optionally set to 0 (unmasked), based on the brcm,int-fwd-mask property,
>> which is what this patch achieves (or tries to). If we write, say
>> 0xffff_feff to the hardware, which has a Write Only register behavior,
>> then we also want to have the mask cache be set to the same value for
>> consistency if nothing else. Am I failing at doing what I just described
>> and also failing at see it?
>
> You write this:
>
>> for (i = 0; i < n_words; i++) {
>> - l1_writel(0xffffffff, cpu->map_base + reg_mask_set(intc, i));
>> - cpu->mask_cache[i] = 0xffffffff;
>> + l1_writel(0xffffffff & ~intc->irq_fwd_mask[i],
>> + cpu->map_base + reg_mask_set(intc, i));
>> + cpu->mask_cache[i] = 0xffffffff & ~intc->irq_fwd_mask[i];
>> }
>
> And I'm saying that this is strictly equivalent to:
>
> for (i = 0; i < n_words; i++) {
> l1_writel(~intc->irq_fwd_mask[i],
> cpu->map_base + reg_mask_set(intc, i));
> cpu->mask_cache[i] = ~intc->irq_fwd_mask[i];
> }
>
> without this 0xffffffff that does exactly nothing (I'm pretty sure the
> compiler drops it anyway).
I understand quickly, you just need to repeat many times, thanks for
bearing with me, this is indeed simpler and clearer.
--
Florian
