linux-kernel - Re: [PATCH] irqchip/bcm-6345-l1: show MMIO address

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Date:   Thu, 16 Mar 2023 18:25:30 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Álvaro Fernández Rojas <noltari@...il.com>,
        jonas.gorski@...il.com, bcm-kernel-feedback-list@...adcom.com,
        tglx@...utronix.de, linux-mips@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] irqchip/bcm-6345-l1: show MMIO address

On 2023-03-16 18:13, Florian Fainelli wrote:
> On 3/16/23 11:07, Álvaro Fernández Rojas wrote:
>> It's safe to show MMIO address.
>> 
>> Signed-off-by: Álvaro Fernández Rojas <noltari@...il.com>
> 
> This is going to be the kernel virtual address, and while on MIPS it
> is easy to resolve to the physical address because these platforms map
> registers through KSEG0/1, on other platforms like ARM/ARM64 the
> kernel virtual addresses are pretty meaningless unless what you want
> to debug is how ioremap() mapped the address.
> 
> I would rather do the following change:
> 
> diff --git a/drivers/irqchip/irq-bcm6345-l1.c 
> b/drivers/irqchip/irq-bcm6345-l1.c
> index 1bd0621c4ce2..832957d363a4 100644
> --- a/drivers/irqchip/irq-bcm6345-l1.c
> +++ b/drivers/irqchip/irq-bcm6345-l1.c
> @@ -261,6 +261,8 @@ static int __init bcm6345_l1_init_one(struct
> device_node *dn,
>         if (!cpu->map_base)
>                 return -ENOMEM;
> 
> +       request_mem_region(res.start, sz, res.name);
> +
>         for (i = 0; i < n_words; i++) {
>                 cpu->enable_cache[i] = 0;
>                 __raw_writel(0, cpu->map_base + reg_enable(intc, i));
> 
> such that this shows up in /proc/iomem. WDYT?

That's certainly much more useful in general.

Also, the current pr_info() is probably pretty useless, given
that the OP was trying to circumvent the obfuscation. Either
printing the PA or removing the message altogether would be
good.

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...