Re: [PATCH v5 7/8] i2c: amd-asf: Clear remote IRR bit to get successive interrupt

[Shyam Sundar S K <Shyam-sundar.S-k@amd.com>]

On 9/14/2024 00:49, Andy Shevchenko wrote:
> On Fri, Sep 13, 2024 at 05:41:09PM +0530, Shyam Sundar S K wrote:
>> To ensure successive interrupts upon packet reception, it is necessary to
>> clear the remote IRR bit by writing the interrupt number to the EOI
>> register. The base address for this operation is provided by the BIOS and
>> retrieved by the driver by traversing the ASF object's namespace.
> 
> ...
> 
>> +	eoi_addr = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> +	if (!eoi_addr)
>> +		return dev_err_probe(&pdev->dev, -EINVAL, "missing MEM resources\n");
>> +
>> +	asf_dev->eoi_base = devm_ioremap(&pdev->dev, eoi_addr->start, resource_size(eoi_addr));
>> +	if (!asf_dev->eoi_base)
>> +		return dev_err_probe(&pdev->dev, -EBUSY, "failed mapping IO region\n");
> 
> Home grown copy of devm_platform_ioremap_resource().
> 

devm_platform_ioremap_resource() internally calls
devm_platform_get_and_ioremap_resource(), performing two main actions:

It uses platform_get_resource().
It then calls devm_ioremap_resource().

However, there's an issue.

devm_ioremap_resource() invokes devm_request_mem_region() followed by
__devm_ioremap(). In this driver, the resource obtained via ASL might
not actually belong to the ASF device address space. Instead, it could
be within other IP blocks of the ASIC, which are crucial for
generating subsequent interrupts (the main focus of this patch). As a
result, devm_request_mem_region() fails, preventing __devm_ioremap()
from being executed.

TL;DR, it’s more appropriate to call platform_get_resource() and
devm_ioremap() separately in this scenario.

Thanks,
Shyam