linux-kernel - Re: [PATCH v2] irqchip/qcom-pdc: add support for v3.2 HW

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Message-ID: <ac1026c7-f446-482a-8abe-ac34786462a6@linaro.org>
Date:   Wed, 23 Aug 2023 10:51:11 +0200
From:   neil.armstrong@...aro.org
To:     "Maulik Shah (mkshah)" <quic_mkshah@...cinc.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>
Cc:     linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] irqchip/qcom-pdc: add support for v3.2 HW

On 23/08/2023 10:25, Maulik Shah (mkshah) wrote:
> Hi,
> 
> On 8/23/2023 1:16 PM, Neil Armstrong wrote:
>> Hi,
>>
>> On 23/08/2023 07:35, Maulik Shah (mkshah) wrote:
>>> Hi Neil,
>>>
>>> @@ -142,8 +163,17 @@ static int qcom_pdc_gic_set_type(struct irq_data *d, unsigned int type)
>>>>           return -EINVAL;
>>>>       }
>>>> -    old_pdc_type = pdc_reg_read(IRQ_i_CFG, d->hwirq);
>>>> -    pdc_reg_write(IRQ_i_CFG, d->hwirq, pdc_type);
>>>> +    if (pdc_version < PDC_VERSION_3_2) {
>>>> +        old_pdc_type = pdc_reg_read(IRQ_i_CFG, d->hwirq);
>>>> +        pdc_reg_write(IRQ_i_CFG, d->hwirq, pdc_type);
>>>> +    } else {
>>>> +        u32 val;
>>>> +
>>>> +        val = pdc_reg_read(IRQ_i_CFG, d->hwirq);
>>>> +        old_pdc_type = val & IRQ_i_CFG_TYPE_MASK;
>>>> +        pdc_reg_write(IRQ_i_CFG, d->hwirq,
>>>> +                  pdc_type | (val & IRQ_i_CFG_IRQ_ENABLE));
>>>> +    }
>>> While above is correct, i don't think we need version check in qcom_pdc_gic_set_type() as bits 0-2 are always for the type in old/new version as mentioned in v1.
>>>
>>> Adding one line after reading old_pdc_type should be good enough.
>>
>> Yes I understood, but while looking at the IRQ_i_CFG bits, I wanted to keep the original
>> driver behavior intact by setting remaining bits to 0.
>>
>> Adding this single line changes that behavior and keeps bits 3-31
>> to the default register value, which may have some consequences.
>>
>> If you consider it's an ok change, then I'll reduce it to this single line.
> Yes this ok change to have single line and should not have  any consequences.

I also remember why, it's about the final check:

184         if (old_pdc_type != pdc_type)
185                 irq_chip_set_parent_state(d, IRQCHIP_STATE_PENDING, false);

We need to strip out remaining bits of old_pdc_type of this won't work as
expected, so I'll change it to :

+       old_pdc_type = pdc_reg_read(IRQ_i_CFG, d->hwirq);
+       pdc_type |= (old_pdc_type & ~IRQ_i_CFG_TYPE_MASK);
+       old_pdc_type &= IRQ_i_CFG_TYPE_MASK;
+       pdc_reg_write(IRQ_i_CFG, d->hwirq, pdc_type);

Is it ok for you ?

Thanks,
Neil


> 
> Thanks,
> Maulik
>