On Thu, May 12, 2016 at 9:07 PM, Christian Lamparter
[off-list ref] wrote:

On Thursday, May 12, 2016 07:26:32 PM Alexandre Courbot wrote:

quoted

On Wednesday, May 11, 2016 6:34:34 PM JST, Christian Lamparter wrote:

quoted

From: ?lvaro Fern?ndez Rojas <redacted>

This patch adds support for defining memory-mapped GPIOs which
are compatible with the existing gpio-mmio interface. The generic
library provides support for many memory-mapped GPIO controllers
that are found in various on-board FPGA and ASIC solutions that
are used to control board's switches, LEDs, chip-selects,
Ethernet/USB PHY power, etc.

For setting GPIO's there are three configurations:

s/GPIO's/GPIOs

OK

quoted

quoted

    1. single input/output register resource (named "dat"),
    2. set/clear pair (named "set" and "clr"),
    3. single output register resource and single input resource
       ("set" and dat").

The configuration is detected by which resources are present.
For the single output register, this drives a 1 by setting a bit
and a zero by clearing a bit.  For the set clr pair, this drives
a 1 by setting a bit in the set register and clears it by setting
a bit in the clear register. The configuration is detected by
which resources are present.

The last sentence of this paragraph repeats for first one.

Ok

quoted

quoted

For setting the GPIO direction, there are three configurations:
    a. simple bidirectional GPIOs that requires no configuration.
    b. an output direction register (named "dirout")
       where a 1 bit indicates the GPIO is an output.
    c. an input direction register (named "dirin")
       where a 1 bit indicates the GPIO is an input.

The first user for this binding is "wd,mbl-gpio".

Reviewed-by: Andy Shevchenko <redacted>
Signed-off-by: ?lvaro Fern?ndez Rojas <redacted>
Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
---
 static void bgpio_write8(void __iomem *reg, unsigned long data)
 {

@@ -569,6 +571,58 @@ static void __iomem *bgpio_map(struct

platform_device *pdev,
    return devm_ioremap_resource(&pdev->dev, r);
 }

+#ifdef CONFIG_OF
+static int bgpio_basic_mmio_parse_dt(struct platform_device *pdev,
+                                struct bgpio_pdata *pdata,
+                                unsigned long *flags)
+{
+   struct device *dev = &pdev->dev;
+
+   pdata->base = -1;
+
+   if (of_property_read_bool(dev->of_node, "no-output"))
+           *flags |= BGPIOF_NO_OUTPUT;

I don't think it is a good idea to add "generic" properties. Whether a
controller is capable of output or not should be determined by its
compatible string only, and not a vague property.

Well, meet the gpios on the MBL. If you want to figure out how WD wired
up these two GPIOs (one is input, the other output), I can sent you a
built-yourself MBL kit. It just needs a 3,5" drive and a 12V 2A power
plug with a standard 5.5mm plug.

quoted

quoted

+
+   return 0;
+}
+
+static const struct of_device_id bgpio_of_match[] = {
+   { .compatible = "wd,mbl-gpio", .data = bgpio_basic_mmio_parse_dt },

Mmm cannot you determine whether your controller is capable of output or
not just from the compatible property here? If so, the
bgpio_basic_mmio_parse_dt seems to be unneeded. If not, then this is
dependent on the wd,mbl-gpio binding and should be renamed accordingly.

Sadly I don't know of any method. The device has two GPIOs one at 0x4e0000000.
The other one is at 0x4e0100000. The address tells me that there are two
external chips connected to the EBC (memory bank - RAM, ROM and DMA chips
go here according to IBM's documentations). Which is not the place you
would expect peripherals.

Ok, if you have no way of figuring that out then this is legit.

quoted

quoted

@@ -646,6 +709,7 @@ MODULE_DEVICE_TABLE(platform, bgpio_id_table);
 static struct platform_driver bgpio_driver = {
    .driver = {
            .name = "basic-mmio-gpio",
+           .of_match_table = of_match_ptr(bgpio_of_match),
    },
    .id_table = bgpio_id_table,
    .probe = bgpio_pdev_probe,

It seems to me that this patch does two things:

1) Add code to support device tree lookup
2) Add support for "wd,mbl-gpio".

If true, these two things should be in their own patches. You should also
have another patch that adds the DT bindings for "wd,mbl-gpio", so I would
do things in that order:

The DT bindings have been merged. That's why I dropped it from the rebase.

quoted

1/3: DT support for basic-mmio-gpio

Sadly, adding the "basic-mmio-gpio" binding is not possible without a ACK from
the device tree maintainers. They have voiced their concerns. I think this was
your post of the discussion on it:
<http://www.spinics.net/lists/devicetree/msg124613.html>

That's why the series was updated around v5 and v6 to use the "wd,mbl-gpio"
binding.

So yes, I wanted to go this route in the beginning as well. But no go.
If we find more devices we could have a "basic-mmio-gpio" class. But
for now, we have to start somewhere.

Ah, I was not suggesting that you add a "basic-mmio-gpio" compatible
property, but that the first patch of the series should add the
infrastructure code required for "wd,mbl-gpio" and the drivers you are
moving to use it in 2/2. That way you separate the addition of support
code to the actual device support.

quoted

2/3: DT bindings for "wd,mbl-gpio" (and have them validated by the DT
people - e.g. do you really need a "reg" property or is it here just to fit
with what bgpio_pdev_probe expects? More about this on 2/2)
3/3: Support for "wd,mbl-gpio" in basic-mmio-gpio

Yes, that would have been nice. And I agree it was the way to do it. But
without the wd,mbl-gpio mapping I would add the bgpio_parse_dt function
without any caller. (As I can't add the compatible = "basic-mmio-gpio", ...)

bgpio_parse_dt() is called from bgpio_pdev_probe(), so whether you
have the mapping or not should not matter, does it?

It's just that there is no reason to add support for WD-MBL in this
patch, and convert other drivers in the next - both are equal users of
the infrastructure code you are adding.

Note that my comments on the next patch suggest deeper changes to this
one - you may want to read them as well (I will ignore v9.1 for now).