regmap: mmio: regression in pre-v4.6-rc1

regmap: mmio: regression in pre-v4.6-rc1

[Alexander Stein]

Hi,

I'm currently trying to get PCIe working on LS1021A (little-endian ARM). For link-detection I need access to a syscon perpheral (SCFG) which is attched to CPU as big-endian.
The corresponding DT part is:

		scfg: scfg@1570000 {
			compatible = "fsl,ls1021a-scfg", "syscon";
			reg = <0x0 0x1570000 0x0 0x10000>;
			big-endian;
		};

Based on current linus's master (a24e3d414e59ac765, "Merge branch 'akpm' (patches from Andrew)") I noticed the access is actually done as little-endian.
I could track it down to commit 922a9f936e40001f ("regmap: mmio: Convert to regmap_bus and fix accessor usage"). Reverting it, the access is fine now and I get my PCIe link.

Best regards,
Alexander

Re: regmap: mmio: regression in pre-v4.6-rc1

[Alexander Stein]

On Wednesday 23 March 2016 09:48:42, Alexander Stein wrote:
> I'm currently trying to get PCIe working on LS1021A (little-endian ARM). For link-detection I need access to a syscon perpheral (SCFG) which is attched to CPU as big-endian.
> The corresponding DT part is:
> 
> 		scfg: scfg@1570000 {
> 			compatible = "fsl,ls1021a-scfg", "syscon";
> 			reg = <0x0 0x1570000 0x0 0x10000>;
> 			big-endian;
> 		};
> 
> Based on current linus's master (a24e3d414e59ac765, "Merge branch 'akpm' (patches from Andrew)") I noticed the access is actually done as little-endian.
> I could track it down to commit 922a9f936e40001f ("regmap: mmio: Convert to regmap_bus and fix accessor usage"). Reverting it, the access is fine now and I get my PCIe link.

Just for the records, this also affects spi-fsl-dspi which is also attached in big-endian.

Best regards,
Alexander

Re: regmap: mmio: regression in pre-v4.6-rc1

[Mark Brown]

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On Wed, Mar 23, 2016 at 09:48:42AM +0100, Alexander Stein wrote:

Please fix your mail client to word wrap within paragraphs at something
substantially less than 80 columns.  Doing this makes your messages much
easier to read and reply to.

> I'm currently trying to get PCIe working on LS1021A (little-endian
> ARM). For link-detection I need access to a syscon perpheral (SCFG)
> which is attched to CPU as big-endian.

Are you *sure* that this is actually big endian?  Are you basing this on
documentation or on what happened to work for you in the past.

> Based on current linus's master (a24e3d414e59ac765, "Merge branch
> 'akpm' (patches from Andrew)") I noticed the access is actually done
> as little-endian.  I could track it down to commit 922a9f936e40001f
> ("regmap: mmio: Convert to regmap_bus and fix accessor usage").
> Reverting it, the access is fine now and I get my PCIe link.

Have you tried tracing through the code to see what ends up happening to
the I/O?  It should come out using your architecture's big endian
accessors.

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Re: regmap: mmio: regression in pre-v4.6-rc1

[Alexander Stein]

On Wednesday 23 March 2016 10:34:15, Mark Brown wrote:
> > I'm currently trying to get PCIe working on LS1021A (little-endian
> > ARM). For link-detection I need access to a syscon perpheral (SCFG)
> > which is attched to CPU as big-endian.
> 
> Are you *sure* that this is actually big endian?  Are you basing this on
> documentation or on what happened to work for you in the past.

Please refer to QorIQ LS1021A Reference Manual (REV 0) table 2.2 (CCSR block 
base address map) which states that this peripheral (among _most_ but not all) 
requires byte swapping. Same for DSPI.
Yeah, it sounds strange.

> > Based on current linus's master (a24e3d414e59ac765, "Merge branch
> > 'akpm' (patches from Andrew)") I noticed the access is actually done
> > as little-endian.  I could track it down to commit 922a9f936e40001f
> > ("regmap: mmio: Convert to regmap_bus and fix accessor usage").
> > Reverting it, the access is fine now and I get my PCIe link.
> 
> Have you tried tracing through the code to see what ends up happening to
> the I/O?  It should come out using your architecture's big endian
> accessors.

In regmap_mmio_gen_context ctx->reg_read is set to regmap_mmio_read32le and 
ctx->reg_write to regmap_mmio_write32le respectively.

I noticed that before that change map->reg_read = _regmap_bus_read and map-
>reg_write = _regmap_bus_raw_write. After that change it is map->reg_read = 
_regmap_bus_reg_read resp. map->reg_write = _regmap_bus_reg_write.
I hope this description is not that confusing.

Best regards,
Alexander

Re: regmap: mmio: regression in pre-v4.6-rc1

[Mark Brown]

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On Wed, Mar 23, 2016 at 12:16:13PM +0100, Alexander Stein wrote:
> On Wednesday 23 March 2016 10:34:15, Mark Brown wrote:

> > Are you *sure* that this is actually big endian?  Are you basing this on
> > documentation or on what happened to work for you in the past.

> Please refer to QorIQ LS1021A Reference Manual (REV 0) table 2.2 (CCSR block 
> base address map) which states that this peripheral (among _most_ but not all) 
> requires byte swapping. Same for DSPI.
> Yeah, it sounds strange.

I don't have that document.

> > Have you tried tracing through the code to see what ends up happening to
> > the I/O?  It should come out using your architecture's big endian
> > accessors.

> In regmap_mmio_gen_context ctx->reg_read is set to regmap_mmio_read32le and 
> ctx->reg_write to regmap_mmio_write32le respectively.

So how does that happen then?  We set these values if the bus is
default, little or native endian but if it's big endian we go into a
completely different case...

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Re: regmap: mmio: regression in pre-v4.6-rc1

[Alexander Stein]

On Wednesday 23 March 2016 11:39:39, Mark Brown wrote:
> On Wed, Mar 23, 2016 at 12:16:13PM +0100, Alexander Stein wrote:
> > On Wednesday 23 March 2016 10:34:15, Mark Brown wrote:
> 
> > > Are you *sure* that this is actually big endian?  Are you basing this on
> > > documentation or on what happened to work for you in the past.
> 
> > Please refer to QorIQ LS1021A Reference Manual (REV 0) table 2.2 (CCSR block 
> > base address map) which states that this peripheral (among _most_ but not all) 
> > requires byte swapping. Same for DSPI.
> > Yeah, it sounds strange.
> 
> I don't have that document.

Nothing wrong with that, I just wanted to state where it is actually documented.

> > > Have you tried tracing through the code to see what ends up happening to
> > > the I/O?  It should come out using your architecture's big endian
> > > accessors.
> 
> > In regmap_mmio_gen_context ctx->reg_read is set to regmap_mmio_read32le and 
> > ctx->reg_write to regmap_mmio_write32le respectively.
> 
> So how does that happen then?  We set these values if the bus is
> default, little or native endian but if it's big endian we go into a
> completely different case...

Well, in regmap_mmio_gen_context config->reg_format_endian is still set to REGMAP_ENDIAN_DEFAULT. of_syscon_register sets config.val_format_endian (notice val_ instead of reg_) depending on "big-endian" (or "little-endian") property.
I'm kinda confused regarding reg_format_endian and val_format_endian. Dunno what should be set in which way.

Best regards,
Alexander

Re: regmap: mmio: regression in pre-v4.6-rc1

[Mark Brown]

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On Wed, Mar 23, 2016 at 12:50:53PM +0100, Alexander Stein wrote:

As I said previously please fix your mail client to word wrap within
paragraphs at something substantially less than 80 columns.  Doing this
makes your messages much easier to read and reply to.

> > > In regmap_mmio_gen_context ctx->reg_read is set to regmap_mmio_read32le and 
> > > ctx->reg_write to regmap_mmio_write32le respectively.

> > So how does that happen then?  We set these values if the bus is
> > default, little or native endian but if it's big endian we go into a
> > completely different case...

> Well, in regmap_mmio_gen_context config->reg_format_endian is still
> set to REGMAP_ENDIAN_DEFAULT. of_syscon_register sets
> config.val_format_endian (notice val_ instead of reg_) depending on
> "big-endian" (or "little-endian") property.  I'm kinda confused
> regarding reg_format_endian and val_format_endian. Dunno what should
> be set in which way.

Ah, I see.  That's definitely broken - if we're changing the value
format we should be checking the value.

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