Message-ID: <20160112101418.GO13633@e106497-lin.cambridge.arm.com>
Date:	Tue, 12 Jan 2016 10:14:18 +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 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".
> 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>;

Best regards,
Liviu

> 
> >Best regards,
> >Liviu
> >
> >>
> >>>
> >>>Best regards,
> >>>Liviu
> >>>
> >>>
> >>>>
> >>>>	Arnd
> >>>>
> >>>
> >>Regards,
> >>Rongrong
> >>
> >
> -- 
> Regards,
> Rongrong
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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