[U-Boot] passing info from SPL to U-Boot

[Tom Rini]

On Wed, Mar 13, 2019 at 10:18:06AM +0100, Heiko Schocher wrote:
> Hello Stefano,
> 
> Am 13.03.2019 um 09:51 schrieb Stefano Babic:
> >Hi Heiko,
> >
> >On 13/03/19 08:44, Heiko Schocher wrote:
> >>Hello Wolfgang,
> >>
> >>Am 12.03.2019 um 18:46 schrieb Wolfgang Denk:
> >>>Dear Tom,
> >>>
> >>>In message <20190312173125.GP4690 at bill-the-cat> you wrote:
> >>>>
> >>>>>I think you were misled by Heiko's description.  What he really ment
> >>>>>was just that the addresses where the boot ROM stored the
> >>>>>information about the boot device etc. gets overwriteen when the SPL
> >>>>
> >>>>For clarity, that's not _quite_ it.  The ROM passes the value in a
> >>>>register and we move that to scratch space, see
> >>>>arch/arm/mach-omap2/lowlevel_init.S and save_boot_params.  This is done
> >>>>on every 32bit Cortex-A TI platform.
> >>>...
> >>>>OK, but here's the problem.  We define off, iirc, 1KiB of that SRAM
> >>>>space as not-stack but scratch space to store stuff in.  The first
> >>>>problem you will hit, if something else touches that scratch space is
> >>>>what Heiko found, the boot value got blown away.
> >>>
> >>>I see.  Well, I think it's best if Heiko explains in detail; what he
> >>>has observed, and what when which part of the information got lost.
> >>>I was just interpreting his mail, so I may easily have misunderstood
> >>>this.
> >>>
> >>>@ Heiko:  Can you please elucidate?
> >>
> >>arch/arm/include/asm/arch-am33xx/omap.h
> >>
> >>  19 #ifdef CONFIG_AM33XX
> >>  20 #define NON_SECURE_SRAM_START   0x402F0400
> >>  21 #define NON_SECURE_SRAM_END     0x40310000
> >>  22 #define NON_SECURE_SRAM_IMG_END 0x4030B800
> >>  23 #elif defined(CONFIG_TI816X) || defined(CONFIG_TI814X)
> >>  24 #define NON_SECURE_SRAM_START   0x40300000
> >>  25 #define NON_SECURE_SRAM_END     0x40320000
> >>  26 #define NON_SECURE_SRAM_IMG_END 0x4031B800
> >>  27 #elif defined(CONFIG_AM43XX)
> >>  28 #define NON_SECURE_SRAM_START   0x402F0400
> >>  29 #define NON_SECURE_SRAM_END     0x40340000
> >>  30 #define NON_SECURE_SRAM_IMG_END 0x40337DE0
> >>  31 #define QSPI_BASE              0x47900000
> >>  32 #endif
> >>  33 #define SRAM_SCRATCH_SPACE_ADDR (NON_SECURE_SRAM_IMG_END - SZ_1K)
> >>  34
> >>
> >>
> >>and with ./include/configs/ti_armv7_common.h
> >>
> >>  69 #ifndef CONFIG_SYS_INIT_SP_ADDR
> >>  70 #define CONFIG_SYS_INIT_SP_ADDR         (NON_SECURE_SRAM_END - \
> >>  71
> >>GENERATED_GBL_DATA_SIZE)
> >>  72 #endif
> >>  73
> >>
> >>include/generated/generic-asm-offsets.h
> >>
> >>   9 #define GENERATED_GBL_DATA_SIZE 224 /* (sizeof(struct global_data) +
> >>15) & ~15  @ */
> >>  10 #define GENERATED_BD_INFO_SIZE 112 /* (sizeof(struct bd_info) + 15)
> >>& ~15       @ */
> >>  11 #define GD_SIZE 224 /* sizeof(struct global_data)       @ */
> >>
> >>
> >>-> CONFIG_SYS_INIT_SP_ADDR = 0x40340000 - 0xe0  = 0x4033ff20
> >>-> SRAM_SCRATCH_SPACE_ADDR = 0x40337DE0 - 0x400 = 0x403379e0
> >>
> >>./arch/arm/include/asm/omap_common.h:
> >>816 #define OMAP_SRAM_SCRATCH_BOOT_PARAMS   (SRAM_SCRATCH_SPACE_ADDR +
> >>0x24)
> >>
> >>OMAP_SRAM_SCRATCH_BOOT_PARAMS = 0x40337a04
> >>
> >>So stack is on a higher address than the scratch space. Stack
> >>addresses decrement on usage, so may they overwrite scratch
> >>space, as SPL functionality grows more and more ...
> >
> >What about to move this area after the initial SP ? This is the same way
> >we do with GENERATED_GBL_DATA_SIZE to avoid to be overwritten.
> 
> If I am not wrong, the value of SRAM_SCRATCH_SPACE_ADDR is not changeable
> as it comes from the ROM bootloader.

No, we define the scratch space, but there's important restrictions.

-- 
Tom
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 819 bytes
Desc: not available
URL: <http://lists.denx.de/pipermail/u-boot/attachments/20190313/f7e5c4a5/attachment.sig>