RE: [PATCH V5 3/3] ARM64 LPC: LPC driver implementation on Hip06

Gabriele Paoloni
2016-11-25T16:29:48Z

Hi Arnd

> -----Original Message-----
> From: Arnd Bergmann [mailto:arnd@arndb.de]
> Sent: 25 November 2016 12:04
> To: Gabriele Paoloni
> Cc: linux-arm-kernel@lists.infradead.org; mark.rutland@arm.com;
> catalin.marinas@arm.com; linux-pci@vger.kernel.org;
> liviu.dudau@arm.com; Linuxarm; lorenzo.pieralisi@arm.com; xuwei (O);
> Jason Gunthorpe; T homas Petazzoni; linux-serial@vger.kernel.org;
> benh@kernel.crashing.org; devicetree@vger.kernel.org; minyard@acm.org;
> will.deacon@arm.com; John Garry; olof@lixom.net; robh+dt@kernel.org;
> bhelgaas@go og le.com; kantyzc@163.com; zhichang.yuan 02@gmail.com;
> linux-kernel@vger.kernel.org; Yuanzhichang; zourongrong@gmail.com
> Subject: Re: [PATCH V5 3/3] ARM64 LPC: LPC driver implementation on
> Hip06
>
> On Friday, November 25, 2016 8:46:11 AM CET Gabriele Paoloni wrote:
> > > From: Arnd Bergmann [mailto:arnd@arndb.de]
> > >
> > > On Wednesday, November 23, 2016 6:07:11 PM CET Arnd Bergmann wrote:
> > > > On Wednesday, November 23, 2016 3:22:33 PM CET Gabriele Paoloni
> > > wrote:
> > > > > From: Arnd Bergmann [mailto:arnd@arndb.de]
> > > > > > On Friday, November 18, 2016 5:03:11 PM CET Gabriele Paoloni
> > > /*
> > > @@ -549,9 +548,14 @@ static int of_translate_one(struct device_node
> > > *parent, struct of_bus *bus,
> > > * that translation is impossible (that is we are not dealing with
> a
> > > value
> > > * that can be mapped to a cpu physical address). This is not
> really
> > > specified
> > > * that way, but this is traditionally the way IBM at least do
> things
> > > + *
> > > + * Whenever the translation fails, the *host pointer will be set
> to
> > > the
> > > + * device that lacks a tranlation, and the return code is relative
> to
> > > + * that node.
> >
> > This seems to be wrong to me. We are abusing of the error conditions.
> > So effectively if there is a buggy DT for an IO resource we end up
> > assuming that we are using a special IO device with unmapped
> addresses.
> >
> > The patch at the bottom apply on top of this one and I think is a
> more
> > reasonable approach
>
> It was meant as a logical extension to the existing interface,
> translating the address as far as we can, and reporting back
> how far we got.
>
> Maybe we can return 'of_root' by instead of NULL to signify
> that we have converted all the way to the root of the DT?
> That would make it more consistent, but slightly more complicated
> for the common case.

Mmm not sure really...the point is that now the **host parameter is
used both as a flag and also in of_translate_ioport...the problem
that I see is where we set the "host" parameter...I have a proposal
below...

[...]

> pci_bus_alloc_resource(struct
> > > pci_bus *bus,
> > > void *alignf_data);
>
> [Many lines of reply trimmed here, please make sure you don't quote too
> much context when you reply, it's really annoying to read through
> it otherwise]

Sorry! I'll take care of this in the future...

>
> > /*
> > + * of_isa_indirect_io - get the IO address from some isa reg
> property value.
> > + * For some isa/lpc devices, no ranges property in ancestor node.
> > + * The device addresses are described directly in their regs
> property.
> > + * This fixup function will be called to get the IO address of
> isa/lpc
> > + * devices when the normal of_translation failed.
> > + *
> > + * @parent: points to the parent dts node;
> > + * @bus: points to the of_bus which can be used to parse
> address;
> > + * @addr: the address from reg property;
> > + * @na: the address cell counter of @addr;
> > + * @presult: store the address paresed from @addr;
> > + *
> > + * return 1 when successfully get the I/O address;
> > + * 0 will return for some failures.
> > + */
> > +static int of_get_isa_indirect_io(struct device_node *parent,
> > + struct of_bus *bus, __be32 *addr,
> > + int na, u64 *presult)
> > +{
> > + unsigned int flags;
> > + unsigned int rlen;
> > +
> > + /* whether support indirectIO */
> > + if (!indirect_io_enabled())
> > + return 0;
> > +
> > + if (!of_bus_isa_match(parent))
> > + return 0;
> > +
> > + flags = bus->get_flags(addr);
> > + if (!(flags & IORESOURCE_IO))
> > + return 0;
> > +
> > + /* there is ranges property, apply the normal translation
> directly. */
> > + if (of_get_property(parent, "ranges", &rlen))
> > + return 0;
> > +
> > + *presult = of_read_number(addr + 1, na - 1);
> > + /* this fixup is only valid for specific I/O range. */
> > + return addr_is_indirect_io(*presult);
> > +}
>
> Right, this would work. The reason I didn't go down this route is
> that I wanted to keep it generic enough to allow doing the same
> for PCI host bridges with a nonlinear mapping of the I/O space.
>
> There isn't really anything special about ISA here, other than the
> fact that the one driver that needs it happens to be for ISA rather
> than PCI.

Yes I see your point please consider the patch at the bottom...

>
> > +/*
> > * Translate an address from the device-tree into a CPU physical
> address,
> > * this walks up the tree and applies the various bus mappings on
> the
> > * way.
> > @@ -600,14 +643,23 @@ static u64 __of_translate_address(struct
> device_node *dev,
> > result = of_read_number(addr, na);
> > break;
> > }
> > + /*
> > + * For indirectIO device which has no ranges property, get
> > + * the address from reg directly.
> > + */
> > + if (of_get_isa_indirect_io(dev, bus, addr, na, &result)) {
> > + pr_debug("isa indirectIO matched(%s)..addr =
> 0x%llx\n",
> > + of_node_full_name(dev), result);
> > + *host = of_node_get(parent);
> > + break;
> > + }
> >
>
> If we do the special case for ISA as you suggest above, I would still
> want
> to keep it in of_translate_ioport(), I think that's a useful change by
> itself in my patch.

This comes without saying...the patch I proposed here already applied on
top of your changes and, in fact, you can see that I set
"*host = of_node_get(parent);" above in my patch to be used by
of_translate_ioport()

>
> Arnde
>
>
>

Below I have reworked my patch (that still applies on top of your one) to
make it not ISA specific.
Notice that of_translate_ioport() still stands and that in addr_is_indirect_io()
we make sure the bus address to be in the bus address range that the special
host operates on...

---
drivers/of/address.c | 56 ++++++++++++++++++++++++++++++++++++++++++++--
include/linux/of_address.h | 17 ++++++++++++++
2 files changed, 71 insertions(+), 2 deletions(-)

diff --git a/drivers/of/address.c b/drivers/of/address.c
index 5decaba..2b34931 100644
--- a/drivers/of/address.c
+++ b/drivers/of/address.c
@@ -540,6 +540,48 @@ static u64 of_translate_one(struct device_node *parent, struct of_bus *bus,
}

/*
+ * of_get_indirect_io - get the IO address from some reg property value.
+ * For some special host devices, we have no ranges property node and
+ * we directly use the bus addresses of the children regs property.
+ * This fixup function will be called to get the IO address of isa/lpc
+ * devices when the normal of_translation failed.
+ *
+ * @parent: points to the parent dts node;
+ * @bus: points to the of_bus which can be used to parse address;
+ * @addr: the address from reg property;
+ * @na: the address cell counter of @addr;
+ * @presult: store the address parsed from @addr;
+ *
+ * return 1 when successfully get the I/O address;
+ * 0 will return for some failures.
+ */
+static int of_get_indirect_io(struct device_node *parent,
+ struct of_bus *bus, __be32 *addr,
+ int na, u64 *presult)
+{
+ unsigned int flags;
+ unsigned int rlen;
+
+ /* whether support indirectIO */
+ if (!indirect_io_enabled())
+ return 0;
+
+ flags = bus->get_flags(addr);
+ if (!(flags & IORESOURCE_IO))
+ return 0;
+
+ /* there is ranges property, apply the normal translation directly. */
+ if (of_get_property(parent, "ranges", &rlen))
+ return 0;
+
+ *presult = of_read_number(addr + 1, na - 1);
+
+ /* check if the bus address falls into the range of
+ * the special host device*/
+ return addr_is_indirect_io(*presult);
+}
+
+/*
* Translate an address from the device-tree into a CPU physical address,
* this walks up the tree and applies the various bus mappings on the
* way.
@@ -601,13 +643,23 @@ static u64 __of_translate_address(struct device_node *dev,
break;
}

+ /*
+ * For indirectIO device which has no ranges property, get
+ * the address from reg directly.
+ */
+ if (of_get_indirect_io(dev, bus, addr, na, &result)) {
+ pr_debug("isa indirectIO matched(%s)..addr = 0x%llx\n",
+ of_node_full_name(dev), result);
+ *host = of_node_get(parent);
+ break;
+ }
+
/* Get new parent bus and counts */
pbus = of_match_bus(parent);
pbus->count_cells(dev, &pna, &pns);
if (!OF_CHECK_COUNTS(pna, pns)) {
- pr_debug("Bad cell count for %s\n",
+ pr_err("Bad cell count for %s\n",
of_node_full_name(dev));
- *host = of_node_get(parent);
break;
}

diff --git a/include/linux/of_address.h b/include/linux/of_address.h
index 3786473..14848d8 100644
--- a/include/linux/of_address.h
+++ b/include/linux/of_address.h
@@ -24,6 +24,23 @@ struct of_pci_range {
#define for_each_of_pci_range(parser, range) \
for (; of_pci_range_parser_one(parser, range);)

+#ifndef indirect_io_enabled
+#define indirect_io_enabled indirect_io_enabled
+static inline bool indirect_io_enabled(void)
+{
+ return false;
+}
+#endif
+
+#ifndef addr_is_indirect_io
+#define addr_is_indirect_io addr_is_indirect_io
+static inline int addr_is_indirect_io(u64 taddr)
+{
+ return 0;
+}
+#endif
+
+
/* Translate a DMA address from device space to CPU space */
extern u64 of_translate_dma_address(struct device_node *dev,
const __be32 *in_addr);
--
2.7.4