On 05/10/2016 08:25 PM, Simon Glass wrote:
Hi Stephen,
On 4 May 2016 at 12:42, Stephen Warren <swar...@wwwdotorg.org> wrote:
On 05/01/2016 01:27 PM, Simon Glass wrote:
Hi Stephen,
On 28 April 2016 at 17:08, Stephen Warren <swar...@wwwdotorg.org> wrote:
From: Stephen Warren <swar...@nvidia.com>
This will allow a driver's bind function to use the driver data. One
example is the Tegra186 GPIO driver, which instantiates child devices
for each of its GPIO ports, yet supports two different HW instances each
with a different set of ports, and identified by the udevice_id .data
field.
Signed-off-by: Stephen Warren <swar...@nvidia.com>
---
drivers/core/device.c | 7 ++++---
drivers/core/lists.c | 6 +++---
drivers/gpio/dwapb_gpio.c | 2 +-
drivers/gpio/s5p_gpio.c | 2 +-
drivers/gpio/sunxi_gpio.c | 2 +-
drivers/gpio/tegra_gpio.c | 2 +-
drivers/mtd/spi/sandbox.c | 2 +-
drivers/net/mvpp2.c | 3 ++-
drivers/pci/pci-uclass.c | 5 ++---
drivers/power/pmic/pmic-uclass.c | 2 +-
drivers/usb/host/usb-uclass.c | 5 ++---
include/dm/device-internal.h | 5 +++--
12 files changed, 22 insertions(+), 21 deletions(-)
I'm not sure this extra parameter carries its weight:
- most callers just pass 0
The same is true of the existing platdata field in many cases.
Yes, but platdata is defined to be needed by bind(), whereas
driver_data is supposed to be used in probe() to find out which
device tree compatible string matched.
This seems to conflict with the documentation in include/dm/device.h; it
claims that platdata is created by calling ofdata_to_platdata() just
before calling probe(), at least for the DT case (for the case where
U_BOOT_DEVICE is used, the platdata is available right from the start).
I couldn't find anywhere in the documentation that states when
driver_data is supposed to be used; could you point me at it so I can
read it?
> Remember that the device tree
properties are not looked at during bind(), only later. So it makes
sense to include platdata in the device_bind() call, but not
driver_data.
Hmm, drivers/gpio/tegra_gpio.c:gpio_tegra_bind() uses DT (which you
wrote or at least converted it to DM and chose where to put the DT
accesses), and you very recently reviewed and applied "video: tegra:
refuse to bind to disabled dcs" which modified
drivers/video/tegra.c:tegra_lcd_bind() to use DT.
Admittedly I do now see the following in doc/driver-model/README.txt:
The device's bind() method is permitted to perform simple actions, but
should not scan the device tree node, not initialise hardware, nor set up
structures or allocate memory. All of these tasks should be left for
the probe() method.
... but then I wonder why that rule was enforced for the patch in this
thread, but not in the other cases?
This inconsistency in review is extremely frustrating to me.
- the field is supposed to be set up by device tree and probing tables,
not code
While the existence of this new parameter does allow arbitrary code to set
the parameter, this patch only actually sets the parameter in the case where
DT and probing tables have determined that value.
I don't think so. That value is set in lists_bind_fdt().
Sure, but that function is only used from 3 places, and explicitly
accepts a parameter to indicate which DT node to instantiate a device
for. It won't work unless a valid DT node is passed to it, and therefore
can only work for DT-based probing.
I wonder if you could set it yourself after calling device_bind()?
The Tegra186 GPIO driver explicitly needs to use the data inside the
driver's bind() function in order to know how many child devices to
instantiate. Setting the value after calling device_bind() (which the
core DM code already does) is too late.
For reference, you can see the exact code at:
http://lists.denx.de/pipermail/u-boot/2016-April/252238.html
"gpio: add Tegra186 GPIO driver"
Search for "tegra186_gpio_bind" and look at the assignment to, and use
of, ctlr_data.
I had also quoted that part of the code in my previous email.
- bind() methods should not care about the driver data (they are not
allowed to touch hardware), so setting it later is fine
Not touching HW is fine, but the driver data can still feed into purely SW
decisions that bind makes. More details below.
- you can already pass platform data to the driver which is the
preferred communication method from a parent to its children
I don't believe this is possible for devices instantiated from DT is it? In
that case, platform data is always NULL:
That's right. For DT the paltform data is set up in the
ofdata_to_platdata() method. Since you are using DT, you should follow
that convention.
This is the opposite of what you said above, which was that platdata is
for bind().
int lists_bind_fdt(struct udevice *parent, const void *blob, int offset,
struct udevice **devp)
...
ret = device_bind(parent, entry, name, NULL, id->data,
offset, &dev);
(That quoted code is with this patch applied, and the NULL value is the
platform data parameter.)
Also it's not clear from your Tegra 186 GPIO patch where you are using
this.
Here's the relevant part from the Tegra186 GPIO driver patch I posted:
+static int tegra186_gpio_bind(struct udevice *parent)
+{
+ struct tegra186_gpio_platdata *parent_plat = parent->platdata;
+ struct tegra186_gpio_ctlr_data *ctlr_data =
+ (struct tegra186_gpio_ctlr_data *)parent->driver_data;
...
+ /* If this is a child device, there is nothing to do here */
+ if (parent_plat)
+ return 0;
...
+ for (port = 0; port < ctlr_data->port_count; port++) {
...
+ plat->name = ctlr_data->ports[port].name;
+ plat->regs = &(regs[ctlr_data->ports[port].offset / 4]);
The data is used to determine how many child devices (one per port) to
create, and the name and register offset of each one. This is modelled after
the logic in the previous Tegra GPIO driver that you wrote, with the
unfortunate modification that the register layout is more "interesting" on
Tegra186, and so we can't determine the number of and parameters for the
child devices purely algorithmically, since the register layout is decidedly
non-linear.
OK I see. This feels like something that your device tree should
describe.
DT generally describes the presence of HW blocks, not the internal
details of those HW blocks, since that is a fixed facet of the hardware
design and can be statically derived from the value of the compatible
property.
Equally, I'm not sure how describing the details of the HW differences
in DT would help. The details need to be known by the driver's bind()
function, which you and the U-Boot documentation both state isn't
allowed to access DT.
Failing that, how about a hard-coded table of information in
the source code? You can look through the table and create the
appropriate child devices.
That is EXACTLY what the code is doing. The only issue is that the
driver supports two different compatible properties and needs to know
which one was found in DT in order to use the right table. That's what
driver_data is; the .data value from the udevice_id/of_match table.
I suppose an alternative would be to create separate U_BOOT_DRIVER()s for
each compatible value with different register layout, and then have the
bind() for each of those call into some common implementation with a
hard-coded parameter. Still, it seems like the usage in the current code is
exactly what udevice_id.data is for; to avoid having to implement separate
functions that do that.
Yes, but you should use different compatible strings for the nodes.
That's EXACTLY what the code does. However, there is currently no way
for bind() to find out which entry in the udevice_id table matched,
since the DM core currently sets driver_data after calling bind() rather
than before.
As
I understand it, you only have a single node, so re-purposing this
does not seem right to me.
I must not understand what you're conveying by "single node" here. To
quote the example from the Tegra186 GPIO DT binding documentation, here
is what the DT looks like:
gpio@2200000 {
compatible = "nvidia,tegra186-gpio";
reg-names = "security", "gpio";
reg =
<0x0 0x2200000 0x0 0x10000>,
<0x0 0x2210000 0x0 0x10000>;
interrupts =
<0 47 IRQ_TYPE_LEVEL_HIGH>,
<0 50 IRQ_TYPE_LEVEL_HIGH>,
<0 53 IRQ_TYPE_LEVEL_HIGH>,
<0 56 IRQ_TYPE_LEVEL_HIGH>,
<0 59 IRQ_TYPE_LEVEL_HIGH>,
<0 180 IRQ_TYPE_LEVEL_HIGH>;
gpio-controller;
#gpio-cells = <2>;
interrupt-controller;
#interrupt-cells = <2>;
};
gpio@c2f0000 {
compatible = "nvidia,tegra186-gpio-aon";
reg-names = "security", "gpio";
reg =
<0x0 0xc2f0000 0x0 0x1000>,
<0x0 0xc2f1000 0x0 0x1000>;
interrupts =
<0 60 IRQ_TYPE_LEVEL_HIGH>;
gpio-controller;
#gpio-cells = <2>;
interrupt-controller;
#interrupt-cells = <2>;
};
Those two HW blocks are roughly but not exactly the same HW. Hence,
there are two compatible values. The two HW blocks are similar enough to
be handled by a single driver though, and hence the udevice_id table has
two entries:
static const struct udevice_id tegra186_gpio_ids[] = {
{
.compatible = "nvidia,tegra186-gpio",
.data = (ulong)&tegra186_gpio_main_data,
},
{
.compatible = "nvidia,tegra186-gpio-aon",
.data = (ulong)&tegra186_gpio_aon_data,
},
{ }
};
The .data value there provides all necessary information for the driver
to handle both HW block designs.
All I need is to be able to access the ".data" from that table in
bind(), whereas the DM core currently doesn't allow that.
Perhaps the creation of the child devices could happen in probe() rather
than bind()? I imagine there's some reason this wouldn't work (such as this
causing the devices to be created too late to be referenced by other
drivers?) or you would have done this in the existing Tegra GPIO driver.
Best not - it is good to have the devices known on start-up. Let me
know if the above solution doesn't work.
I must admit, I didn't see any solution offered in your email.
If the child devices must be created in bind(), which I do agree makes
sense, then bind() must be able to determine which udevice_id table
entry is related to the device being bound. Is there another way to do
that besides using the driver_data from the udevice_id table? I suppose
I could make bind() go read the compatible property from the DT node for
the device, and manually search through the udevice_id table and find
the matching entry. However, that would be duplicating work the DM core
has already done, and exposes by setting the device's driver_data right
after calling the driver's bind(), so doesn't make sense to me.
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