Hello Giorgio, On 4/6/20 5:15 PM, Giorgio wrote: > Searching in the Armv7-A ref. man. here: > > https://static.docs.arm.com/ddi0406/cd/DDI0406C_d_armv7ar_arm.pdf > > at B4.1.43 (page B4 - 1554) I found that the reset value of this cp15 reg. > is UNKNOWN and I can also verify this. Moreover the reg. must also be > banked: there is a copy in secure mode and one in nonsecure mode. > My test consists in reading the register just before and just after > the call to arm_smccc_smc(0, 0, 0, 0, 0, 0, 0, 0, &res): > > static u32 read_dacr(void) > { > unsigned int reg; > > asm volatile ("mrc p15, 0, %0, c3, c0, 0\n" : "=r"(reg)); > return reg; > } > > ... > > int __armv7_secure_monitor_install(void) > { > ... > printf("%s: 1) dacr: 0x%08x\n",__func__,read_dacr()); > > /* Initialize the secure monitor */ > arm_smccc_smc(0, 0, 0, 0, 0, 0, 0, 0, &res); > > /* We're in nonsecure mode now */ > > printf("%s: 2) dacr: 0x%08x\n",__func__,read_dacr()); > > return 0; > } > > and here is what I get: > > samx7: / smc -n > __armv7_secure_monitor_install: 1) dacr: 0x00000001 > __armv7_secure_monitor_install: 2) dacr: 0xdbf7afaa > > If I write a 0x1 or a 0x3 to DACR just before enabling the MMU in > nonsecure mode then barebox does not hang. Oh! seems i have been lucky so far: __armv7_secure_monitor_install: 1) dacr: 0x00000001 __armv7_secure_monitor_install: 2) dacr: 0xa133ad17 Yes, we will want to call set_domain(DOMAIN_CLIENT) somewhere, maybe just before set_ttbr? Do you want to send a patch? (Your other i.MX7 patches are welcome as well :-) Cheers and thanks for debugging this Ahmad > > giorgio > > On 2020-04-06 08:16, Ahmad Fatoum wrote: >> Hello Giorgio, >> >> On 4/3/20 3:47 PM, Giorgio wrote: >>> Hi Ahmad, >>> >>> thank you for the detailed explanations, I'll have a look >>> at the armv7 ref. manual for more background. >>> >>> I wanted just to note, the problem is specifically linked >>> to enabling the MMU: >>> >>> in arch/arm/cpu/cache-armv7.S: >>> >>> >>> orrne r0, r0, #1 @ MMU enabled >>> ... >>> mcr p15, 0, r0, c1, c0, 0 @ load control register >>> >>> without the 'orrne ...' the imx7 does not hang. >> >> I can't reproduce this exact problem. My setup: >> >> - i.MX7D sabresd board, >> - imx_v7_defconfig >> - check out of upstream/next, commit 5931fe40 ("Merge branch 'for-next/zii' into next") >> - revert of commit 8b2104d ("driver: Call of_clk_set_defaults for each probed device") >> - nv bootm.secure_state=nonsecure >> >> With this, I didn't observe any barebox hangs[1] while preparing a Linux net boot. >> What's your setup? >> >> [1]: Linux still hangs due to what I assume to be a psci issue, kernel log says >> "unsupported enable-method property: psci" before getting stuck durcing SDHCI probe >> > -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox
