Re: [PATCH v1 3/3] ARM64 LPC: update binding doc

From: Rongrong Zou <zourongrong@huawei.com>
To: <liviu.dudau@arm.com>
Cc: Rongrong Zou <zourongrong@gmail.com>,
	<devicetree@vger.kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Arnd Bergmann <arnd@arndb.de>, Corey Minyard <minyard@acm.org>,
	<gregkh@linuxfoundation.org>, Will Deacon <will.deacon@arm.com>,
	<linux-kernel@vger.kernel.org>, <linuxarm@huawei.com>,
	<benh@kernel.crashing.org>,
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v1 3/3] ARM64 LPC: update binding doc
Date: Tue, 12 Jan 2016 19:05:29 +0800	[thread overview]
Message-ID: <5694DDF9.1050902@huawei.com> (raw)
In-Reply-To: <20160112101418.GO13633@e106497-lin.cambridge.arm.com>

在 2016/1/12 18:14, liviu.dudau@arm.com 写道:
> On Tue, Jan 12, 2016 at 05:25:56PM +0800, Rongrong Zou wrote:
>> 在 2016/1/12 17:07, liviu.dudau@arm.com 写道:
>>> On Tue, Jan 12, 2016 at 10:39:36AM +0800, Rongrong Zou wrote:
>>>> On 2016/1/12 0:14, liviu.dudau@arm.com wrote:
>>>>> On Mon, Jan 04, 2016 at 12:13:05PM +0100, Arnd Bergmann wrote:
>>>>>> On Sunday 03 January 2016 20:24:14 Rongrong Zou wrote:
>>>>>>> 在 2015/12/31 23:00, Rongrong Zou 写道:
>>>>>>>> 2015-12-31 22:40 GMT+08:00 Arnd Bergmann <arnd@arndb.de <mailto:arnd@arndb.de>>:
>>>>>>>>   > On Thursday 31 December 2015 22:12:19 Rongrong Zou wrote:
>>>>>>>>   > > 在 2015/12/30 17:06, Arnd Bergmann 写道:
>>>>>>>>   > > > On Tuesday 29 December 2015 21:33:52 Rongrong Zou wrote:
>>>>>>>>   >
>>>>>>>>   > The DT sample above looks good in principle. I believe what you are missing
>>>>>>>>   > here is code in your driver to scan the child nodes to create the platform
>>>>>>>>   > devices. of_bus_isa_translate() should work with your definition here
>>>>>>>>   > and create the correct IORESOURCE_IO resources. You don't have any MMIO
>>>>>>>>   > resources, so the absence of a ranges property is ok. Maybe all you
>>>>>>>>   > are missing is a call to of_platform_populate() or of_platform_bus_probe()?
>>>>>>>>   >
>>>>>>>>
>>>>>>>> You are right. thanks, i'll try on test board .  if i get the correct result , the new patch
>>>>>>>> will be sent later. By the way, it's my another email account use when i at home.
>>>>>>>
>>>>>>> I tried, and there need some additional changes.
>>>>>>>
>>>>>>> isa@a01b0000 {
>>>>>>>
>>>>>>> /*the node name should start with "isa", because of below definition
>>>>>>> * static int of_bus_isa_match(struct device_node *np)
>>>>>>> * {
>>>>>>> *	return !strcmp(np->name, "isa");
>>>>>>> * }
>>>>>>
>>>>>> Looks good. It would be nicer to match on device_type than on name,
>>>>>> but this is ancient code and it's probably best not to touch it
>>>>>> so we don't accidentally break some old SPARC or PPC system.
>>>>>>
>>>>>>> */
>>>>>>> 	compatible = "low-pin-count";
>>>>>>> 	device_type = "isa";
>>>>>>> 	#address-cells = <2>;
>>>>>>> 	#size-cells = <1>;
>>>>>>> 	reg = <0x0 0xa01b0000 0x0 0x10000>;
>>>>>>> 	ranges = <0x1 0x0 0x0 0x0 0x1000>;
>>>>>>> /*
>>>>>>> *  ranges is required, then i can get the IORESOURCE_IO <0xe4,4> from "reg = <0x1, 0x000000e4, 4>".
>>>>>>> *
>>>>>>> */
>>>>>>> 	ipmi_0:ipmi@000000e4{
>>>>>>> 		device_type = "ipmi";
>>>>>>> 		compatible = "ipmi-bt";
>>>>>>> 		reg = <0x1 0x000000e4 0x4>;
>>>>>>> };
>>>>>>>
>>>>>>
>>>>>> This looks wrong: the property above says that the I/O port range is
>>>>>> translated to MMIO address 0x00000000 to 0x00010000, which is not
>>>>>> true on your hardware. I think this needs to be changed in the code
>>>>>> so the ranges property is not required for I/O ports.
>>>>>>
>>>>>>> drivers\of\address.c
>>>>>>> static int __of_address_to_resource(struct device_node *dev,
>>>>>>>                   const __be32 *addrp, u64 size, unsigned int flags,
>>>>>>>                   const char *name, struct resource *r)
>>>>>>> {
>>>>>>>           u64 taddr;
>>>>>>>
>>>>>>>           if ((flags & (IORESOURCE_IO | IORESOURCE_MEM)) == 0)
>>>>>>>                   return -EINVAL;
>>>>>>>           taddr = of_translate_address(dev, addrp);
>>>>>>>           if (taddr == OF_BAD_ADDR)
>>>>>>>                   return -EINVAL;
>>>>>>>           memset(r, 0, sizeof(struct resource));
>>>>>>>           if (flags & IORESOURCE_IO) {
>>>>>>>                   unsigned long port;
>>>>>>>
>>>>>>> /*****************************************************************/
>>>>>>> /*legacy port(< 0x1000) is reserved, and need no translation here*/
>>>>>>> /*****************************************************************/
>>>>>>>                   if(taddr + size < PCIBIOS_MIN_IO){
>>>>>>>                           r->start = taddr;
>>>>>>>                           r->end = taddr + size - 1;
>>>>>>>                   }
>>>>>>
>>>>>> I don't like having a special case based on the address here,
>>>>>> the same kind of hack might be needed for PCI I/O spaces in
>>>>>> hardware that uses an indirect method like your LPC bus
>>>>>> does, and the code above will not work on any LPC implementation
>>>>>> that correctly multiplexes its I/O ports with the first PCI domain.
>>>>>>
>>>>>> I think it would be better to avoid translating the port into
>>>>>> a physical address to start with just to translate it back into
>>>>>> a port number, what we need instead is the offset between the
>>>>>> bus specific port number and the linux port number. I've added
>>>>>> Liviu to Cc, he wrote this code originally and may have some idea
>>>>>> of how we could do that.
>>>>>
>>>>> Hi,
>>>>
>>>> Hi Liviu,
>>>>
>>>> Thanks for reviewing this.
>>>>
>>>>>
>>>>> Getting back to work after a longer holiday, my brain might not be running
>>>>> at full speed here, so I'm trying to clarify things a bit here.
>>>>>
>>>>> It looks to me like Rongrong is trying to trap the inb()/outb() calls that he
>>>>> added to arm64 by patch 1/3 and redirect those operations to the memory
>>>>> mapped LPC driver. I think the whole redirection and registration of inb/outb
>>>>> ops can be made cleaner, so that the general concept resembles the DMA ops
>>>>> registration? (I have this mental picture that what Rongrong is trying to do
>>>>> is similar to what a DMA engine does, except this is slowing down things to
>>>>> byte level). If that is done properly in the parent node, then we should not
>>>>> care what the PCIBIOS_MIN_IO value is as the inb()/outb() calls will always
>>>>> go through the redirection for the children.
>>>>>
>>>>> As for the ranges property: does he wants the ipmi-bt driver to see in the
>>>>> reg property the legacy ISA I/O ports values or the CPU addresses? If the former,
>>>>> then I agree that the range property should not be required, but also the
>>>>> reg values need to be changed (drop the top bit). If the later, then the
>>>>> ranges property is required to do the proper translation.
>>>>
>>>> The former, thanks.
>>>>
>>>>>
>>>>> Rongrong, removing the ranges property and with a reg = <0xe4 0x4> property
>>>>> in the ipmi-bt node, what IO_RESOURCE type resources do you get back from
>>>>> the of_address_to_resource() translation?
>>>>
>>>> I want to get IORESOURCE_IO type resource, but if the parent node drop the
>>>> "rangs" property, the of_address_to_resource() translation will return with -EINVAL.
>>>
>>> Have you tracked what part of the code is sensitive to the presence of "ranges"
>>> property? Does of_get_address() call returns the IO_RESOURCE flag set without "ranges"?
>>>
>>
>>
>> Yes, IO_RESOURCE flag can be get without "ranges".
>> I tracked the code, it is at of_translate_one(), Below is the calling infomation.
>>
>> of_address_to_resource-> __of_address_to_resource ->of_translate_address->
>> __of_translate_address(dev, in_addr, "ranges")->of_translate_one()
>>
>>
>> static int of_translate_one(struct device_node *parent, struct of_bus *bus,
>> 			    struct of_bus *pbus, __be32 *addr,
>> 			    int na, int ns, int pna, const char *rprop)
>> {
>> 	const __be32 *ranges;
>> 	unsigned int rlen;
>> 	int rone;
>> 	u64 offset = OF_BAD_ADDR;
>>
>> 	ranges = of_get_property(parent, rprop, &rlen);
>> 	if (ranges == NULL && !of_empty_ranges_quirk(parent)) {
>> 		pr_debug("OF: no ranges; cannot translate\n");
>> 		return 1;
>> 	}
>> 	...
>> }
>
> OK, looking at of_translate_one() comments it looks like a missing "ranges" property is
> only accepted on PowerPC. I suggest you have an empty "ranges" property in your isa
> parent node, that will signal to the OF parsing code that the mapping is 1:1. Then have
> the IPMI node use the reg = <0x0 0xe4 4>; property values instead of reg = <0x1 0xe4 4>;

But in this condition, I still can't get the right resource type IORESOURCE_IO, I just get
the MMIO resource E4:E7. Please see the url at https://lkml.org/lkml/2016/1/5/199, the empty
ranges has been discussed.

>
> Best regards,
> Liviu
>
>>
>>> Best regards,
>>> Liviu
>>>
>>>>
>>>>>
>>>>> Best regards,
>>>>> Liviu
>>>>>
>>>>>
>>>>>>
>>>>>> 	Arnd
>>>>>>
>>>>>
>>>> Regards,
>>>> Rongrong
>>>>
>>>
>> --
>> Regards,
>> Rongrong
>>
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>

-- 
Regards,
Rongrong