Re: [RFC PATCH] of: platform: Skip mapping of interrupts in of_device_alloc()

Hi Rob,

Thank you for the review.

On Thu, Dec 9, 2021 at 3:08 AM Rob Herring [off-list ref] wrote:

On Wed, Dec 8, 2021 at 6:11 PM Lad Prabhakar
[off-list ref] wrote:

quoted

of_device_alloc() in early boot stage creates a interrupt mapping if
there exists a "interrupts" property in the node.

For hierarchical interrupt domains using "interrupts" property in the node
bypassed the hierarchical setup and messed up the irq setup.

This patch adds a check in of_device_alloc() to skip interrupt mapping if
"not-interrupt-producer" property is present in the node. This allows
nodes to describe the interrupts using "interrupts" property.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
---
Hi All,

Spawning from discussion [1], here is simple patch (not the ideal probably
welcome for suggestions) from stopping the OF code from creating a map for
the interrupts when using "interrupts" property.

[1] https://lore.kernel.org/lkml/87pmqrck2m.wl-maz@kernel.org/ (local)
    T/#mbd1e47c1981082aded4b32a52e2c04291e515508

Cheers,
Prabhakar
---
 drivers/of/platform.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index b3faf89744aa..629776ca1721 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c

@@ -114,7 +114,7 @@ struct platform_device *of_device_alloc(struct device_node *np,
                                  struct device *parent)
 {
        struct platform_device *dev;
-       int rc, i, num_reg = 0, num_irq;
+       int rc, i, num_reg = 0, num_irq = 0;
        struct resource *res, temp_res;

        dev = platform_device_alloc("", PLATFORM_DEVID_NONE);

@@ -124,7 +124,14 @@ struct platform_device *of_device_alloc(struct device_node *np,
        /* count the io and irq resources */
        while (of_address_to_resource(np, num_reg, &temp_res) == 0)
                num_reg++;
-       num_irq = of_irq_count(np);
+
+       /*
+        * we don't want to map the interrupts of hierarchical interrupt domain
+        * into the parent domain yet. This will be the job of the hierarchical
+        * interrupt driver code to map the interrupts as and when needed.
+        */
+       if (!of_property_read_bool(np, "not-interrupt-producer"))
+               num_irq = of_irq_count(np);

The property won't fly for sure. A compatible match table could work
here, but I don't really want another temporary solution.

Agreed.

quoted

        /* Populate the resource table */
        if (num_irq || num_reg) {

@@ -140,7 +147,7 @@ struct platform_device *of_device_alloc(struct device_node *np,
                        rc = of_address_to_resource(np, i, res);
                        WARN_ON(rc);
                }
-               if (of_irq_to_resource_table(np, res, num_irq) != num_irq)
+               if (num_irq && of_irq_to_resource_table(np, res, num_irq) != num_irq)

You might want to look at commit 9ec36cafe43b ("of/irq: do irq
resolution in platform_get_irq"). The intent was to remove this code,
but looks like the cleanup has a ways to go 7 years on. Primarily,
it's convert any platform_get_resource(pdev, IORESOURCE_IRQ, n) call
to platform_get_irq(). There's ~169 of those.

That's a good point converting all the drivers to use
platform_get_irq() so that the resource allocation happens on demand,
and the above code can be dropped.

There are probably some open coded accesses to pdev->resources too,
but I didn't spot any.

I'll have a closer look.

Cheers,
Prabhakar

Rob