From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sean Anderson Date: Sun, 9 Aug 2020 15:23:31 -0400 Subject: MAIX: CONFIG_SYS_INIT_SP_ADDR In-Reply-To: <72DF1720-F679-43D4-A386-A1FFC3FE1243@gmx.de> References: <4183c14e-66f1-fe9b-b4f3-42862d124e05@gmx.de> <2d865aae-e0e9-12f9-03eb-616a35285e3d@gmail.com> <72DF1720-F679-43D4-A386-A1FFC3FE1243@gmx.de> Message-ID: List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On 8/9/20 3:16 PM, Heinrich Schuchardt wrote: > Am 9. August 2020 18:35:45 MESZ schrieb Sean Anderson : >> On 8/9/20 12:14 PM, Heinrich Schuchardt wrote: >>> Hello Sean, >>> >>> while trying to understand the handling of SMP I stumbled of this >> question: >>> >>> Why did you define CONFIG_SYS_INIT_SP_ADDR as an odd number on the >> MAIX >>> in commit a7c81fc85326 ("riscv: Add Sipeed Maix support") while the >>> other RISC-V boards use an even number: >>> >>> include/configs/sifive-fu540.h:29: >>> 29 | #define CONFIG_SYS_INIT_SP_ADDR (CONFIG_SYS_SDRAM_BASE + >> SZ_2M) >>> >>> include/configs/qemu-riscv.h:22: >>> 22 | #define CONFIG_SYS_INIT_SP_ADDR (CONFIG_SYS_SDRAM_BASE + >> SZ_2M) >>> >>> include/configs/sipeed-maix.h:13: >>> 13 | #define CONFIG_SYS_INIT_SP_ADDR 0x803FFFFF >>> >>> I always thought that RISC-V stack pointers must be 16 byte aligned: >>> >>> Cf. https://riscv.org/wp-content/uploads/2015/01/riscv-calling.pdf >>> >>> "In the standard RISC-V calling convention, the stack grows downward >> and >>> the stack pointer is always kept 16-byte aligned." >> >> Because that is the top of (non-ai) ram. And it gets 16-byte aligned by >> call_board_init_f anyway. >> >> --Sean > > Top of RAM is the place to which we want to relocate U-Boot. But furthermore this value minus a multiple of16KiB is also used for the stack lication of the secondary CPU. > > Shouldn't we better use the same definition as the other boards? > Sorry, I misspoke earlier, it's actually the top of ram minus 2M. If you would like to use a different value, it's fine to me, but I don't think it changes much. --Sean