imx6 i2c controller setup

elliott1609 — Wed, 19 Feb 2025 01:46:07 GMT

What must be initialized to access the three I2C controllers built into an imx6?

They are accessed through memory addresses beginning at 0x21a0000.
Despite initializing the IOMUX, clocks, AIPSTZ. and virtual memory pages, (but possibly with errors) all reads from the these memory locations return 0x50085008.

What more than this (in pairs for clock and data)?
1: MUX: 2 assignments like this
*(unsigned long*)(0x20E03B8) = 0x4001b8b1; // (IOMUXC_SW_PAD_CTL_PAD_EIM_DATA21)

2: clock: this looks ok but is it? (runtime output) CCM_CSCMR1: 0x20C401C = 0x900000

3: imx6 "AHB to IP Bridge (AIPSTZ): (runtime output) AIPSTZ2_MPR: 0x217C000 = 0x77777777

4: page tables for virtual to physical addressing, virtual=physical

Re: imx6 i2c controller setup

pengyong_zhang — Tue, 04 Mar 2025 02:29:12 GMT

Hi @elliott1609

Sorry to reply late, But could you explain more details about your question?

How did you access the three I2C controllers now? And what is your result?

B.R

Re: imx6 i2c controller setup

elliott1609 — Tue, 04 Mar 2025 03:55:50 GMT

Linux on the Phytec Mira board correctly accesses a tri-color LED connected to I2C1 and NXP PCA9533 with these commands:

Linux on the Phytec Mira board correctly accesses a tri-color LED connected to I2C1 and NXP PCA9533 with these commands: root@phyboard-mira-imx6-3:mira-red# pwd /sys/devices/platform/dimleds/leds/mira-red root@phyboard-mira-imx6-3:mira-red# ls -l total 0 lrwxrwxrwx 1 root root 0 Jun 15 17:58 device -> ../../../dimleds/ drwxr-xr-x 2 root root 0 Jun 15 17:58 power/ lrwxrwxrwx 1 root root 0 Apr 28 2022 subsystem -> ../../../../../class/leds/ -rw-r--r-- 1 root root 4096 Jun 15 17:58 brightness -r--r--r-- 1 root root 4096 Jun 15 17:58 max_brightness -rw-r--r-- 1 root root 0 Jun 15 17:58 trigger -rw-r--r-- 1 root root 4096 Apr 28 2022 uevent root@phyboard-mira-imx6-3:mira-red# echo 1 > brightness

This works too...

i2cdetect -l i2c-0 i2c 21a0000.i2c I2C adapter i2c-1 i2c 21a4000.i2c I2C adapter i2c-2 i2c 21a8000.i2c I2C adapter

This works too...

root@phyboard-mira-imx6-3:~# i2cdetect -y 0 0 1 2 3 4 5 6 7 8 9 a b c d e f 00: -- -- -- -- -- -- -- -- 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 60: -- -- UU -- -- -- -- -- UU -- -- -- -- -- -- --

But if I try to display I/O memory for the first I2C controller - segmentation fault!

root@phyboard-mira-imx6-3:~# devmem2 0x21a0000 /dev/mem opened. [ 133.730598] 8<--- cut here --- Memory mapped at address 0xb6f750[ 133.734931] Unhandled fault: page domain fault (0x01b) at 0x0046087e 00. [ 133.744145] pgd = 372d4450 [ 133.747281] [0046087e] *pgd=4c289831 [ 133.750871] Internal error: : 1b [#1] SMP ARM [ 133.755233] Modules linked in: cfg80211 coda_vpu v4l2_jpeg imx_vdoa etnaviv dw_hdmi_ahb_audio [ 133.763795] CPU: 2 PID: 375 Comm: devmem2 Not tainted 5.15.102-bsp-yocto-ampliphy-i.mx6-pd22.1.1 #1 [ 133.772850] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree) [ 133.779380] PC is at imx6q_pcie_abort_handler+0x4/0x6c [ 133.784545] LR is at do_DataAbort+0x38/0xbc [ 133.788739] pc : [<c059f2b8>] lr : [<c0113fd0>] psr: 600f0193 [ 133.795011] sp : c2c4ff88 ip : c130a66c fp : 00000002 [ 133.800240] r10: 00000077 r9 : 00000000 r8 : c059f2b4 [ 133.805468] r7 : c2c4ffb0 r6 : b6f75000 r5 : c130a6ec r4 : 00001018 [ 133.812000] r3 : 0046087e r2 : c2c4ffb0 r1 : 00001018 r0 : b6f75000 [ 133.818532] Flags: nZCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment none [ 133.825763] Control: 10c5387d Table: 1297804a DAC: 00000051 [ 133.831512] Register r0 information: non-paged memory [ 133.836573] Register r1 information: non-paged memory [ 133.841630] Register r2 information: non-slab/vmalloc memory [ 133.847301] Register r3 information: non-paged memory [ 133.852358] Register r4 information: non-paged memory [ 133.857415] Register r5 information: non-slab/vmalloc memory [ 133.863079] Register r6 information: non-paged memory [ 133.868136] Register r7 information: non-slab/vmalloc memory [ 133.873801] Register r8 information: non-slab/vmalloc memory [ 133.879465] Register r9 information: NULL pointer [ 133.884174] Register r10 information: non-paged memory [ 133.889318] Register r11 information: non-paged memory [ 133.894461] Register r12 information: non-slab/vmalloc memory [ 133.900212] Process devmem2 (pid: 375, stack limit = 0x45ccccb7) [ 133.906225] Stack: (0xc2c4ff88 to 0xc2c50000) [ 133.910592] ff80: 01366000 00000025 01366190 b6f77200 0046087e 200f0030 [ 133.918778] ffa0: ffffffff 10c5387d 10c5387d c0100e64 00000000 00000000 00000001 00000008 [ 133.926963] ffc0: b6f75000 00001000 021a0000 00000003 b6f75000 00000000 00000077 00000002 [ 133.935147] ffe0: 00471f98 be96fba8 b6e6f96b 0046087e 200f0030 ffffffff 00000000 00000000 [ 133.943332] [<c059f2b8>] (imx6q_pcie_abort_handler) from [<c0113fd0>] (do_DataAbort+0x38/0xbc) [ 133.951965] [<c0113fd0>] (do_DataAbort) from [<c0100e64>] (__dabt_usr+0x44/0x60) [ 133.959376] Exception stack(0xc2c4ffb0 to 0xc2c4fff8) [ 133.964434] ffa0: 00000000 00000000 00000001 00000008 [ 133.972619] ffc0: b6f75000 00001000 021a0000 00000003 b6f75000 00000000 00000077 00000002 [ 133.980804] ffe0: 00471f98 be96fba8 b6e6f96b 0046087e 200f0030 ffffffff [ 133.987426] Code: c10428d0 c10428b4 c1042898 e592303c (e5933000) [ 133.993527] ---[ end trace 79bea8ac688e94bd ]--- Segmentation fault

Here are two other attempts to access the I2C controller I/O address space, this time with barebox...

Hit m for menu or any to stop autoboot: 2 barebox@PHYTEC phyCORE-i.MX6 Quad with NAND:/ mmuinfo 0x21a0000 PAR result for 0x021a0000: privileged read: 0x021a0090 Physical Address [31:12]: 0x021a0000 Reserved [11]: 0x0 Not Outer Shareable [10]: 0x0 Non-Secure [9]: 0x0 Impl. def. [8]: 0x0 Shareable [7]: 0x1 Inner mem. attr. [6:4]: 0x1 (0b001 Strongly-ordered) Outer mem. attr. [3:2]: 0x0 (0b00 Non-cacheable) SuperSection [1]: 0x0 Failure [0]: 0x0 privileged write: 0x021a0090 Physical Address [31:12]: 0x021a0000 Reserved [11]: 0x0 Not Outer Shareable [10]: 0x0 Non-Secure [9]: 0x0 Impl. def. [8]: 0x0 Shareable [7]: 0x1 Inner mem. attr. [6:4]: 0x1 (0b001 Strongly-ordered) Outer mem. attr. [3:2]: 0x0 (0b00 Non-cacheable) SuperSection [1]: 0x0 Failure [0]: 0x0

Barebox again showing (I believe) that something is blocking access to the I/O address space for all three I2C controllers ...

barebox@PHYTEC phyCORE-i.MX6 Quad with NAND:/ md -l 0x219FFF0+0x20 0219fff0: 00000000 00000000 00000000 00000000 ................ 021a0000: xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx ................ barebox@PHYTEC phyCORE-i.MX6 Quad with NAND:/ md -l 0x21abff0+0x20 021abff0: xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx ................ 021ac000: 00000000 00000000 00000000 00000000 ................

My (short) BARE METAL program correctly accesses UART2, the green SOM LED, and the three LEDS on the Mira "expansion board"

I believe my program fails to control the tri-color LED attached to the PCA9533 because something is blocking memory access to I2C controller registers beginning at 21a_0000. Why do I conclude that? Because ALL reads from ANY I2C register (frequency, status. etc) return 0x50085008

My program's output (via UART2)...

IOMUXC_SW_MUX_CTL_PAD_GPIO04 0x20E0238 = 0x5 IOMUXC_SW_PAD_CTL_PAD_GPIO04 0x20E0608 = 0x1B0B0 GPIO05 direction extension green: 0x20AC004 = 0x20000000 R0: 0xC5187F (SCTRL) R1: 0x0 R2: 0x918048 (translation table base 0) CCM_CCGR2: 0x20C4070 = 0xFFFFFFFF CCM_CBCMR: 0x20C4018 = 0x11204 CCM_CBCDR: 0x20C4014 = 0x18D00 CCM_CSCMR1: 0x20C401C = 0x900000 AIPSTZ1_MPR: 0x207C000 = 0x77777777 AIPSTZ2_MPR: 0x217C000 = 0x77777777 AIPSTZ2_OPACR1: 0x217C044 = 0x0 IOMUXC_SW_PAD_CTL_PAD_EIM_DATA21: 0x20E03B8 = 0x1B8B1 I2C1 frequency: 0x21A0004 = 0x50085008 I2C1_I2SR at start: 0x21A000C = 0x50085008I2C RXAK timeout! 0x21A000C = 0x50085008I2C RXAK timeout! 0x21A000C = 0x50085008I2C RXAK timeout! 0x21A000C = 0x50085008 RV-4162-C7 real-time clock...I2C RXAK timeout! 0x21A000C = 0x50085008I2C RXAK timeout! 0x21A000C = 0x50085008

Re: imx6 i2c controller setup

pengyong_zhang — Tue, 11 Mar 2025 03:04:10 GMT

Hi @elliott1609

What is your BSP version? You can use the ./memtool tool read and write the I2C controller.

B.R

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