Hi Sven,
On Thu, Dec 30, 2021 at 6:22 PM Sven Schwermer sven@svenschwermer.de wrote:
Hi Fabio,
Thank you for the hint. That's a _very_ useful document. In the meantime, I have been able to boot my Linux FIT image straight from SPL on my i.MX6ULL platform.
Glad you got it to work. It would be nice if you could submit a patch adding a document adapted for i.MX6ULL.
I have, however, noticed that Linux boots much faster when launched from u-boot proper compared to SPL. Time to (initramfs) init is 1.2s vs. 5s. That is with identical FIT images (kernel, device tree, initramfs, kernel command line). I ruled out differing core clock rates (both run at 396MHz), caches (caches seem to be disabled before handing over to Linux) and differing load addresses (might cause additional relocations, copies).
What other setup could u-boot proper do that would make Linux boot faster that I haven't thought about?
Looking at your previous log, I see that you boot from serial download mode.
I recall seeing such a slow boot behavior when booting from SDP and this was fixed by the following commit:
commit c5437e5b8aff9c952ebaab9be7670439c141e4e7 Author: Ye Li ye.li@nxp.com Date: Mon May 14 09:44:29 2018 -0300
imx: Enable ACTLR.SMP bit for all i.MX cortex-a7 platforms
According to the Cortex-A7 TRM, for ACTLR.SMP bit "You must ensure this bit is set to 1 before the caches and MMU are enabled, or any cache and TLB maintenance operations are performed". ROM sets this bit in normal boot flow, but when in serial download mode, it is not set. Here we add it in u-boot as a common flow for all i.MX cortex-a7 platforms, including mx7d, mx6ul/ull and mx7ulp.
Signed-off-by: Ye Li ye.li@nxp.com [fabio: adapted to U-Boot mainline codebase and make checkpatch happy] Signed-off-by: Fabio Estevam fabio.estevam@nxp.com
Such slow boot is not observed if you boot from other media, such as eMMC, for example.
You could try performing the setting of ACTLR.SMP bit inside SPL. Currently, it is done only inside U-Boot proper.
Hope this helps.