linuxkpi: Add i2c support

[manu]

Summary

Add i2c support to linuxkpi. This is needed by drm-kmod.
For every i2c_adapter added by i2c_add_adapter we add a child to the
device named "lkpi_iic". This child handle the conversion between
Linux i2c_msgs to FreeBSD iic_msgs.
For every i2c_adapter added by i2c_bit_add_bus we add a child to the
device named "lkpi_iicbb". This child handle the conversion between
Linux i2c_msgs to FreeBSD iic_msgs.
With the help of iic(4), this expose the i2c controller to userspace
allowing a user to query DDC information from a monitor.
e.g.: i2c -f /dev/iic0 -a 0x28 -c 128 -d r
will query the standard EDID from the monitor if plugged.

The bitbang part (lkpi_iicbb) isn't tested at all for now as I don't have
compatible hardware (all my hardware have native i2c controller).

Tested on: Intel Skylake, AMD Picasso, AMD Polaris (arm64).
Sponsored by: Beckhoff Automation GmbH & Co. KG

[manu]

To use with https://github.com/freebsd/drm-kmod/commit/0d7cacc62d4277486bfff79e3bdac66045de2667
I plan to send a mail for a CFT as some part of this code isn't tested (lkpi_iicbb part).

[• hselasky]

Looks good.

sys/compat/linuxkpi/common/src/linux_i2c.c

152

For small number of nmsgs you may want to allocate on the stack? Depends how frequently the function is used.

[val_packett.cool]

You're missing a

MODULE_DEPEND(linuxkpi, iicbus, IICBUS_MINVER, IICBUS_PREFVER, IICBUS_MAXVER);

line — with the patch as-is I get

[257] link_elf_obj: symbol iicbus_driver undefined
[257] linker_load_file: /boot/kernel/linuxkpi.ko - unsupported file type

and so on (on my config where iicbus is not built-in).

---

On my Vega 56, the bus is not working — nothing probes, edid command results in i2c: ioctl(I2CRDWR) failed: Input/output error. compat.linuxkpi.amdgpu_hw_i2c was 0 by default but booting with it set to 1 didn't change anything.

[manu]

In D33053#746603, @greg_unrelenting.technology wrote:

You're missing a

MODULE_DEPEND(linuxkpi, iicbus, IICBUS_MINVER, IICBUS_PREFVER, IICBUS_MAXVER);

line — with the patch as-is I get

[257] link_elf_obj: symbol iicbus_driver undefined
[257] linker_load_file: /boot/kernel/linuxkpi.ko - unsupported file type

and so on (on my config where iicbus is not built-in).

Oops, thanks I'll update the patch.

---

On my Vega 56, the bus is not working — nothing probes, edid command results in i2c: ioctl(I2CRDWR) failed: Input/output error. compat.linuxkpi.amdgpu_hw_i2c was 0 by default but booting with it set to 1 didn't change anything.

But amdgpu found the screen or nothing works ?
May I ask for the pci id ?

[wulf]

sys/compat/linuxkpi/common/src/linux_i2c.c

152

For small number of nmsgs you may want to allocate on the stack? Depends how frequently the function is used.

FreeBSD struct iic_msg definition

/* Designed to be compatible with linux's struct i2c_msg */
struct iic_msg
{
        uint16_t        slave;
        uint16_t        flags;
#define IIC_M_WR        0       /* Fake flag for write */
#define IIC_M_RD        0x0001  /* read vs write */
#define IIC_M_NOSTOP    0x0002  /* do not send a I2C stop after message */
#define IIC_M_NOSTART   0x0004  /* do not send a I2C start before message */
        uint16_t        len;    /* msg length */
        uint8_t *       buf;
};

looks very close to proposed LKPI struct i2c_msg definition

#define I2C_M_RD        0x0001
#define I2C_M_NOSTART   0x0002
#define I2C_M_STOP      0x0004
struct i2c_msg {
        uint16_t addr;
        uint16_t flags;
        uint16_t len;
        uint8_t *buf;
};

I think that malloc can be converted to cast here

[val_packett.cool]

In D33053#746767, @manu wrote:

But amdgpu found the screen or nothing works ?
May I ask for the pci id ?

The screen (over DP 1.2) works great as usual, nothing broke. ID is 1002:687F.

[manu]

In D33053#746603, @greg_unrelenting.technology wrote:

You're missing a

MODULE_DEPEND(linuxkpi, iicbus, IICBUS_MINVER, IICBUS_PREFVER, IICBUS_MAXVER);

line — with the patch as-is I get

[257] link_elf_obj: symbol iicbus_driver undefined
[257] linker_load_file: /boot/kernel/linuxkpi.ko - unsupported file type

and so on (on my config where iicbus is not built-in).

---

On my Vega 56, the bus is not working — nothing probes, edid command results in i2c: ioctl(I2CRDWR) failed: Input/output error.

And you have that for all iic node in /dev ? It's normal to have this for uninitialized hardware (like some unconnected edp or something like that).

compat.linuxkpi.amdgpu_hw_i2c was 0 by default but booting with it set to 1 didn't change anything.

amdgpu_hw_i2c is not taken into account if the chip has DC support (so anything > Sea Island).
I hadn't realized that before so I might have a way to test lkpi_iicbb with my hardward.

sys/compat/linuxkpi/common/src/linux_i2c.c

152

Mhm true, it seems that I just need to rewrite the flags part.

[val_packett.cool]

In D33053#747336, @manu wrote:

amdgpu_hw_i2c is not taken into account if the chip has DC support (so anything > Sea Island).
I hadn't realized that before so I might have a way to test lkpi_iicbb with my hardward.

yeah just found that out via some printf debugging :) So the interesting thing is, all the linuxkpi devices exposed to userspace via /dev/iicN hit amdgpu_dm_i2c_xfer, but the driver's internal handling of monitor hotplug actually uses drm_dp_i2c_xfer instead (no messages logged from DC!).
amdgpu_dm_i2c_xfer goes down the hardware path, and ends up with I2C_CHANNEL_OPERATION_ENGINE_BUSY on the second operation.