Re: [RFCv3 3/3] interconnect: imx: Add platform driver for imx8mm

[Angus Ainslie <angus@akkea.ca>]

Hi Leonard,

On 2019-08-21 07:26, Martin Kepplinger wrote:
> On 21.08.19 16:21, Leonard Crestez wrote:
>> On 21.08.2019 17:03, Martin Kepplinger wrote:
>>> On 06.08.19 12:55, Leonard Crestez wrote:
>>>> This adds a platform driver for the i.MX8MM SoC.
>>>> 
>>>> Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
>>>> Signed-off-by: Alexandre Bailon <abailon@baylibre.com>
>>>> ---
>>>>   drivers/interconnect/imx/Kconfig          |   4 +
>>>>   drivers/interconnect/imx/Makefile         |   1 +
>>>>   drivers/interconnect/imx/imx8mm.c         | 114 
>>>> ++++++++++++++++++++++
>>>>   include/dt-bindings/interconnect/imx8mm.h |  49 ++++++++++
>>>>   4 files changed, 168 insertions(+)
>>>>   create mode 100644 drivers/interconnect/imx/imx8mm.c
>>>>   create mode 100644 include/dt-bindings/interconnect/imx8mm.h
>>> 
>>> Do you plan to add such a driver for imx8mq too?
>> 
>> Yes! The topology is different (serving different IP blocks) but no
>> functional code changes are required between 8mm 8mn 8mq.
>> 
>> I already wrote the code and tested it but didn't post because I want 
>> to
>> get the core parts in first. I periodically push my "full"
>> work-in-progress to github:
>> 
>> https://github.com/cdleonard/linux/commits/next_imx8mm_busfreq
>> 
>> You need out-of-tree ATF changes or devfreq probe will fail:
>> 
>> https://github.com/cdleonard/arm-trusted-firmware/commits/imx_2.0.y_busfreq
>> 
> 
> Thanks for the update, that's good to hear. I'll get back to you when I
> come around to test this and wish you good progress until then :)
> 

I've taken up this work while Martin is on leave.

I've integrated your u-boot and ATF on our board and I have a couple of 
questions. Our board is running imx8mq B0 (Rev 2.0) silicon.

It looks like this line limits the training frequencies to 800 MHz and 
166 MHz

https://source.puri.sm/Librem5/uboot-imx/blob/busfreq/board/purism/librem5_devkit/lpddr4_timing_b0.c#L1365

Does 100 MHz and 25 MHz not work on B0 ?

I added the ddrc_and noc opp as well as the 166MHz opp

https://source.puri.sm/angus.ainslie/linux-next/blob/busfreq/arch/arm64/boot/dts/freescale/imx8mq.dtsi#L214

I also added the interconnects ( do we need them on imx8mq ? )

https://source.puri.sm/angus.ainslie/linux-next/blob/busfreq/arch/arm64/boot/dts/freescale/imx8mq.dtsi#L990

I had to add a hack as the PM QoS was limiting the bus speed to 399MHz , 
if you have any ideas why that would be appreciated.

https://source.puri.sm/angus.ainslie/linux-next/blob/busfreq/drivers/devfreq/devfreq.c#L143

The driver is probing

[   12.136537] bus: 'platform': driver_probe_device: matched device 
3d400000.dram-controller with driver imx-ddrc-devfrq
[   12.147259] bus: 'platform': really_probe: probing driver 
imx-ddrc-devfreq with device 3d400000.dram-controller
[   12.157382] imx-ddrc-devfreq 3d400000.dram-controller: no pinctrl 
handle
[   12.164197] arm_smcc rate 0 800000000
[   12.167880] arm_smcc rate 1 166750000
[   12.171778] of: _opp_add_static_v2: turbo:0 rate:25000000 uv:0 
uvmin:0 uvmax:0 latency:0
[   12.179994] of: _opp_add_static_v2: turbo:0 rate:100000000 uv:0 
uvmin:0 uvmax:0 latency:0
[   12.188311] of: _opp_add_static_v2: turbo:0 rate:166750000 uv:0 
uvmin:0 uvmax:0 latency:0
[   12.196606] of: _opp_add_static_v2: turbo:0 rate:800000000 uv:0 
uvmin:0 uvmax:0 latency:0
[   12.204930] imx-ddrc-devfreq 3d400000.dram-controller: events from 
pmu imx8_ddr0
[   12.212403] Added freq 0 25000000
[   12.215742] Added freq 1 100000000
[   12.219177] Added freq 2 166750000
[   12.222648] Added freq 3 800000000
[   12.226105] device: 'devfreq0': device_add
[   12.230287] PM: Adding info for No Bus:devfreq0
[   12.234864] driver: 'imx-ddrc-devfreq': driver_bound: bound to device 
'3d400000.dram-controller'
[   12.243699] bus: 'platform': really_probe: bound device 
3d400000.dram-controller to driver imx-ddrc-devfreq

Add seems to run correctly until it tries to adjust the clock to 166MHz

[   19.555482] ddrc checking rate 800000000 166750000
[   19.555489] ddrc checking rate 166750000 166750000
[   19.560442] bus: 'usb-serial': really_probe: bound device ttyUSB0 to 
driver option1
[   19.568751] imx-ddrc-devfreq 3d400000.dram-controller: ddrc about to 
change freq 800000000 to 166750000

And the board hangs there. Any ideas on how to get past this ?

Thanks
Angus

>                         martin
> 
> 
> 
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