topic PCIe and GPU issues on iMX8MM when using 4GB RAM in i.MX Processors

PCIe and GPU issues on iMX8MM when using 4GB RAM

rodrigo_travess — Wed, 28 Oct 2020 17:11:09 GMT

Hello,

We're testing the NXP ANDROID Q10.0.0_2.3.0 release on our own board, which has an iMX8MM and 4GB of LPDDR4 memory, and we're observing both display and PCIe issues whenever we configure U-Boot to use all 4GB (using the imx8mm_evk_4g_android_defconfig).

The display issue happens after Android is initialized and consists of some parts of the display showing the expected content and other parts flickering with contents of old frames.

As for the PCIe, we have a WiFi module connected to it, and although the PCIe driver itself doesn't show any errors, the Wifi module driver fails during initialization.

Both problems only happen when 4G is enabled on U-boot, by setting the following lines in the file include/configs/imx8mm_evk_android.h.

#define PHYS_SDRAM_2 0x100000000

#define PHYS_SDRAM_2_SIZE 0x40000000 /* 1GB */

If we restrict to only 3GB of memory, none of the issues happen.

I read on the i.MX 8M Mini Reference Manual that only 3GB of RAM memory is available to all modules, and the rest can only be used by the ARM Cores, so I wonder if there might be some memory allocation issue on the GPU and PCIe drivers.

Re: PCIe and GPU issues on iMX8MM when using 4GB RAM

igorpadykov — Thu, 29 Oct 2020 00:26:06 GMT

Hi rodrigo_travess

one can try attached patch.

Best regards
igor

Re: PCIe and GPU issues on iMX8MM when using 4GB RAM

rodrigo_travess — Thu, 29 Oct 2020 12:18:08 GMT

Hi Igor,

Unfortunately, the suggested patch didn't solve either of the issues. Also, I should note that the patch was probably targeted on a much older kernel version, as our device tree didn't have a linux'cma entry, and I added one myself to be consistent with the patch.

Any other suggestion we could try?

Best regards

Rodrigo

Re: PCIe and GPU issues on iMX8MM when using 4GB RAM

igorpadykov — Thu, 29 Oct 2020 14:05:22 GMT

I also sent you patches via mail, had you tried them.

Best regards
igor

Re: PCIe and GPU issues on iMX8MM when using 4GB RAM

rodrigo_travess — Tue, 03 Nov 2020 09:48:46 GMT

Hi Igor Padykov,

Thank you for your support so far.

I tried the patches you sent by email with no luck. The two issues are still there. The release we are using (android-10.0.0_2.3.0) already included most of the changes from the patches.

Best regards,
Rodrigo

Re: PCIe and GPU issues on iMX8MM when using 4GB RAM

matt_frandsen — Wed, 25 Aug 2021 17:06:08 GMT

@rodrigo_travess Any solution to this? I am seeing similar issues with the flickering. @igorpadykov