Re: RFC Need advice on reworking gpio-ep93xx.c to DT support
From: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Date: 2021-03-23 06:58:14
Hello Arnd! On Mon, 2021-03-22 at 23:31 +0100, Arnd Bergmann wrote:
Unfortunately, building a multiplatform kernel makes the kernel image somewhat larger because it includes the code for CONFIG_OF, though it does not have the runtime overhead for the DT data structures that you get when running a DT-enabled kernel. Enabling CONFIG_USE_OF increased the ep93xx_defconfig build for me by 128KB, replacing the private clk driver with CONFIG_COMMON_CLOCK (and no driver) on top added another 50KB, and finally enabling multiplatform added another 2KB. In total, that is 2.7% total bloat in just the kernel image
This doesn't sound so bad as I expected. I still had no chance to figure out much bigger increase from 5.4 to 5.12 ;)
text data bss dec hex filename 5677321 1119704 90556 6887581 69189d build/tmp/vmlinux 5782854 1143720 92188 7018762 6b190a build/tmp/vmlinux-use_of 5830020 1153408 89396 7072824 6bec38 build/tmp/vmlinux-of+clk 5829320 1153920 91308 7074548 6bf2f4 build/tmp/vmlinux-multi I also think at some point in the distant future we will require DT boot for everything, but that probably comes after most ARMv4T and earlier machines have fallen out of use. I'd like to get a feeling for how EP93xx fits in there, can you say what memory configurations are widely deployed and how
The systems I know have 32MB RAM and 16MB Flash (but only 2MB was reserved for compressed kernel back then).
long you expect them to receive kernel upgrades in the future? Are these systems that will definitely get put out of use at a particular time (e.g. mobile phone infrastructure for older networks or fixed-time support contracts), or are these systems that you expect to keep patching until the hardware dies?
Yes, I expect them to work (and be patched) until they die and this may take another decade ;) -- Alexander Sverdlin.