Date:	Tue, 12 Jan 2016 09:07:22 +0000
From:	liviu.dudau@....com
To:	Rongrong Zou <zourongrong@...il.com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	linux-arm-kernel@...ts.infradead.org,
	Rongrong Zou <zourongrong@...wei.com>,
	devicetree@...r.kernel.org, benh@...nel.crashing.org,
	Corey Minyard <minyard@....org>, gregkh@...uxfoundation.org,
	Will Deacon <will.deacon@....com>,
	linux-kernel@...r.kernel.org, linuxarm@...wei.com,
	Catalin Marinas <catalin.marinas@....com>
Subject: Re: [PATCH v1 3/3] ARM64 LPC: update binding doc

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"?

Best regards,
Liviu

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

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

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