Message-ID: <20160112112741.GP13633@e106497-lin.cambridge.arm.com>
Date:	Tue, 12 Jan 2016 11:27:41 +0000
From:	liviu.dudau@....com
To:	Rongrong Zou <zourongrong@...wei.com>
Cc:	Rongrong Zou <zourongrong@...il.com>, devicetree@...r.kernel.org,
	Catalin Marinas <catalin.marinas@....com>,
	Arnd Bergmann <arnd@...db.de>, Corey Minyard <minyard@....org>,
	gregkh@...uxfoundation.org, Will Deacon <will.deacon@....com>,
	linux-kernel@...r.kernel.org, linuxarm@...wei.com,
	benh@...nel.crashing.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v1 3/3] ARM64 LPC: update binding doc

On Tue, Jan 12, 2016 at 07:05:29PM +0800, Rongrong Zou wrote:
> 在 2016/1/12 18:14, liviu.dudau@....com 写道:
> >On Tue, Jan 12, 2016 at 05:25:56PM +0800, Rongrong Zou wrote:
> >>在 2016/1/12 17:07, liviu.dudau@....com 写道:
> >>>On Tue, Jan 12, 2016 at 10:39:36AM +0800, Rongrong Zou wrote:
> >>>>On 2016/1/12 0:14, liviu.dudau@....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@...db.de <mailto:arnd@...db.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@...b0000 {
> >>>>>>>
> >>>>>>>/*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@...000e4{
> >>>>>>>		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".

Earlier, you said this ^

> >>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.

So, when you use an empty "ranges" of_get_address() doesn't return the right flags? What resource
do you actually get, MMIO is not a valid value.

Liviu

> 
> -- 
> Regards,
> Rongrong
> 

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
    ¯\_(ツ)_/¯

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