Re: [PATCH V11 3/3] irqchip: qcom: Add IRQ combiner driver

[Agustin Vega-Frias <agustinv@codeaurora.org>]

Hi Andy,

On 2017-01-25 19:44, Andy Shevchenko wrote:
> On Fri, Jan 20, 2017 at 4:34 AM, Agustin Vega-Frias
> <agustinv@codeaurora.org> wrote:
>> Driver for interrupt combiners in the Top-level Control and Status
>> Registers (TCSR) hardware block in Qualcomm Technologies chips.
>> 
>> An interrupt combiner in this block combines a set of interrupts by
>> OR'ing the individual interrupt signals into a summary interrupt
>> signal routed to a parent interrupt controller, and provides read-
>> only, 32-bit registers to query the status of individual interrupts.
>> The status bit for IRQ n is bit (n % 32) within register (n / 32)
>> of the given combiner. Thus, each combiner can be described as a set
>> of register offsets and the number of IRQs managed.
> 
>> +static inline u32 irq_register(int irq)
>> +{
>> +       return irq / REG_SIZE;
>> +}
>> +
>> +static inline u32 irq_bit(int irq)
>> +{
>> +       return irq % REG_SIZE;
>> +
>> +}
> 
> Besides extra line I do not see a benefit of those helpers. On first
> glance they even increase characters to type.
> 

Will remove these.

>> +static inline int irq_nr(u32 reg, u32 bit)
>> +{
>> +       return reg * REG_SIZE + bit;
>> +}
> 
> This one might make sense.
> 
>> +static void combiner_handle_irq(struct irq_desc *desc)
>> +{
>> +       struct combiner *combiner = irq_desc_get_handler_data(desc);
>> +       struct irq_chip *chip = irq_desc_get_chip(desc);
>> +       u32 reg;
>> +
>> +       chained_irq_enter(chip, desc);
>> +
>> +       for (reg = 0; reg < combiner->nregs; reg++) {
>> +               int virq;
>> +               int hwirq;
>> +               u32 bit;
>> +               u32 status;
>> +
>> +               bit = readl_relaxed(combiner->regs[reg].addr);
>> +               status = bit & combiner->regs[reg].enabled;
>> +               if (!status)
>> +                       pr_warn_ratelimited("Unexpected IRQ on CPU%d: 
>> (%08x %08lx %p)\n",
>> +                                           smp_processor_id(), bit,
>> +                                           
>> combiner->regs[reg].enabled,
>> +                                           combiner->regs[reg].addr);
>> +
> 
>> +               while (status) {
>> +                       bit = __ffs(status);
>> +                       status &= ~(1 << bit);
> 
> Interesting way of for_each_set_bit() ?
> 

I'm leaving this as-is since in arm64 using __ffs can be optimized
better by using the bic instruction.

>> +                       hwirq = irq_nr(reg, bit);
>> +                       virq = irq_find_mapping(combiner->domain, 
>> hwirq);
>> +                       if (virq > 0)
>> +                               generic_handle_irq(virq);
>> +
>> +               }
>> +       }
>> +
>> +       chained_irq_exit(chip, desc);
>> +}
>> +
> 
>> +/*
>> + * irqchip callbacks
>> + */
> 
> Useless.
> 

Will remove

>> +/*
>> + * irq_domain_ops callbacks
>> + */
> 
> Ditto.
> 

Will remove

>> +/*
>> + * Device probing
>> + */
> 
> Ditto.
> 

Will remove

>> +static acpi_status count_registers_cb(struct acpi_resource *ares, 
>> void *context)
>> +{
>> +       int *count = context;
> 
> I would consider to define a struct. It would be easy to extend if 
> needed and...
> 

The intent here is always to get the count so I don't see value
in adding the struct.

>> +
>> +       if (ares->type == ACPI_RESOURCE_TYPE_GENERIC_REGISTER)
>> +               ++(*count);
> 
> ...allows not to use such of constructions. (I think above is
> equivalent to ++*count).
> 

IMHO having the parentheses makes the code clearer.

>> +       return AE_OK;
> 
>> +}
>> +
>> +static int count_registers(struct platform_device *pdev)
>> +{
>> +       struct acpi_device *adev = ACPI_COMPANION(&pdev->dev);
> 
> You don't use adev, so, ACPI_HANDLE() ?
> 

Will change

>> +       acpi_status status;
>> +       int count = 0;
>> +
>> +       if (!acpi_has_method(adev->handle, METHOD_NAME__CRS))
>> +               return -EINVAL;
>> +
>> +       status = acpi_walk_resources(adev->handle, METHOD_NAME__CRS,
>> +                                    count_registers_cb, &count);
>> +       if (ACPI_FAILURE(status))
>> +               return -EINVAL;
>> +       return count;
>> +}
> 
> Oh, since you are using this just as a helper to get count first, why
> not to combine this in one callback?
> What's the benefit of separation?
> 

This is because we do an allocation based on the count first.

>> +
>> +struct get_registers_context {
>> +       struct device *dev;
>> +       struct combiner *combiner;
>> +       int err;
>> +};
>> +
>> +static acpi_status get_registers_cb(struct acpi_resource *ares, void 
>> *context)
>> +{
>> +       struct get_registers_context *ctx = context;
>> +       struct acpi_resource_generic_register *reg;
>> +       phys_addr_t paddr;
>> +       void __iomem *vaddr;
>> +
>> +       if (ares->type != ACPI_RESOURCE_TYPE_GENERIC_REGISTER)
>> +               return AE_OK;
>> +
>> +       reg = &ares->data.generic_reg;
>> +       paddr = reg->address;
>> +       if ((reg->space_id != ACPI_SPACE_MEM) ||
>> +           (reg->bit_offset != 0) ||
>> +           (reg->bit_width > REG_SIZE)) {
>> +               dev_err(ctx->dev, "Bad register resource @%pa\n", 
>> &paddr);
>> +               ctx->err = -EINVAL;
>> +               return AE_ERROR;
>> +       }
>> +
>> +       vaddr = devm_ioremap(ctx->dev, reg->address, REG_SIZE);
>> +       if (IS_ERR(vaddr)) {
>> +               dev_err(ctx->dev, "Can't map register @%pa\n", 
>> &paddr);
>> +               ctx->err = PTR_ERR(vaddr);
>> +               return AE_ERROR;
>> +       }
> 
> This all sounds to me like an OperationalRegion. But I'm not sure it's
> suitable here.
> Do you have ACPI table carved in stone?
> 

I decided to go with registers because in some cases these might be non-
contiguous.

>> +
>> +       ctx->combiner->regs[ctx->combiner->nregs].addr = vaddr;
>> +       ctx->combiner->nirqs += reg->bit_width;
>> +       ctx->combiner->nregs++;
>> +       return AE_OK;
>> +}
>> +
>> +static int get_registers(struct platform_device *pdev, struct 
>> combiner *comb)
>> +{
>> +       struct acpi_device *adev = ACPI_COMPANION(&pdev->dev);
>> +       acpi_status status;
>> +       struct get_registers_context ctx;
>> +
>> +       if (!acpi_has_method(adev->handle, METHOD_NAME__CRS))
>> +               return -EINVAL;
>> +
>> +       ctx.dev = &pdev->dev;
>> +       ctx.combiner = comb;
>> +       ctx.err = 0;
>> +
>> +       status = acpi_walk_resources(adev->handle, METHOD_NAME__CRS,
>> +                                    get_registers_cb, &ctx);
>> +       if (ACPI_FAILURE(status))
>> +               return ctx.err;
>> +       return 0;
>> +}
>> +
>> +static int __init combiner_probe(struct platform_device *pdev)
>> +{
>> +       struct combiner *combiner;
>> +       size_t alloc_sz;
>> +       u32 nregs;
>> +       int err;
>> +
>> +       nregs = count_registers(pdev);
>> +       if (nregs <= 0) {
>> +               dev_err(&pdev->dev, "Error reading register 
>> resources\n");
>> +               return -EINVAL;
>> +       }
>> +
>> +       alloc_sz = sizeof(*combiner) + sizeof(struct combiner_reg) * 
>> nregs;
>> +       combiner = devm_kzalloc(&pdev->dev, alloc_sz, GFP_KERNEL);
>> +       if (!combiner)
>> +               return -ENOMEM;
>> +
>> +       err = get_registers(pdev, combiner);
>> +       if (err < 0)
>> +               return err;
>> +
>> +       combiner->parent_irq = platform_get_irq(pdev, 0);
>> +       if (combiner->parent_irq <= 0) {
>> +               dev_err(&pdev->dev, "Error getting IRQ resource\n");
>> +               return -EPROBE_DEFER;
>> +       }
>> +
>> +       combiner->domain = irq_domain_create_linear(pdev->dev.fwnode, 
>> combiner->nirqs,
>> +                                                   &domain_ops, 
>> combiner);
>> +       if (!combiner->domain)
>> +               /* Errors printed by irq_domain_create_linear */
>> +               return -ENODEV;
>> +
>> +       irq_set_chained_handler_and_data(combiner->parent_irq,
>> +                                        combiner_handle_irq, 
>> combiner);
>> +
>> +       dev_info(&pdev->dev, "Initialized with [p=%d,n=%d,r=%p]\n",
>> +                combiner->parent_irq, combiner->nirqs, 
>> combiner->regs[0].addr);
>> +       return 0;
>> +}
>> +
>> +static const struct acpi_device_id qcom_irq_combiner_ids[] 
>> __dsdt_irqchip = {
>> +       { "QCOM80B1", },
>> +       { }
>> +};
>> +
>> +static struct platform_driver qcom_irq_combiner_probe = {
>> +       .driver = {
>> +               .name = "qcom-irq-combiner",
> 
>> +               .owner = THIS_MODULE,
> 
> Do you still need this?
> 

Will remove

Thanks,
Agustin

>> +               .acpi_match_table = ACPI_PTR(qcom_irq_combiner_ids),
>> +       },
> 
> --
> With Best Regards,
> Andy Shevchenko

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Technologies, Inc.
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