From: Srinivas Ramana <sramana@codeaurora.org> To: "Ramana, Srinivas" <sramana@qti.qualcomm.com> Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: Improper TTBCR for arm 32bit kernel decompression Date: Sat, 10 Sep 2016 11:20:05 +0530 [thread overview] Message-ID: <57D39F0D.8070803@codeaurora.org> (raw) In-Reply-To: <alpine.LFD.2.20.1609091334120.14769@knanqh.ubzr> On 09/09/2016 11:06 PM, Nicolas Pitre wrote: > On Fri, 9 Sep 2016, Srinivas Ramana wrote: > >> Hello, >> >> While trying to boot arm-32 bit kernel, I came across a problem where TTBCR is >> in improper state. If the bootloader uses the long descriptor format and jumps >> to kernel decompressor code, TTBCR may not be in the right state. So, as soon >> as the MMU is enabled, execution can not proceed further. >> >> Before enabling the MMU, it is required to clear the TTBCR.PD0 field to use >> TTBR0 for translation table walks. Also, TTBCR.N should be reset to '0' to >> indicate the correct base address width. The 'commit dbece45894d3a ("ARM: >> 7501/1: decompressor: reset ttbcr for VMSA ARMv7 cores")' does the reset of >> TTBCR.N, but doesn't consider all the bits for the size of TTBCR.N. >> >> when i tried the below change where i explicitly clear TTBCR.PD0 and use >> correct mask for TTBCR.N, I see proper memory after MMU is enabled and >> decompression succeeds. >> >> Request your comments on the change below. If it looks good, I can submit a >> patch for inclusion. >> >> ---------------------8<---------------------------------- >> diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S >> index af11c2f..5769f1f 100644 >> --- a/arch/arm/boot/compressed/head.S >> +++ b/arch/arm/boot/compressed/head.S >> @@ -779,7 +779,8 @@ __armv7_mmu_cache_on: >> orrne r0, r0, #1 @ MMU enabled >> movne r1, #0xfffffffd @ domain 0 = client >> bic r6, r6, #1 << 31 @ 32-bit translation system >> - bic r6, r6, #3 << 0 @ use only ttbr0 >> + bic r6, r6, #7 << 0 @ width of base address field >> + bic r6, r6, #1 << 4 @ use only ttbr0 > > You could combine those instructions like this: > > bic r6, r6, #(7 << 0) | (1 << 4) @ use only ttbr0 Sure, Thanks for the suggestion. I can incorporate this and submit a patch. Can i use your Acked-by? Thanks, -- Srinivas R > > Nicolas > -- > To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc., is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.
WARNING: multiple messages have this Message-ID (diff)
From: sramana@codeaurora.org (Srinivas Ramana) To: linux-arm-kernel@lists.infradead.org Subject: Improper TTBCR for arm 32bit kernel decompression Date: Sat, 10 Sep 2016 11:20:05 +0530 [thread overview] Message-ID: <57D39F0D.8070803@codeaurora.org> (raw) In-Reply-To: <alpine.LFD.2.20.1609091334120.14769@knanqh.ubzr> On 09/09/2016 11:06 PM, Nicolas Pitre wrote: > On Fri, 9 Sep 2016, Srinivas Ramana wrote: > >> Hello, >> >> While trying to boot arm-32 bit kernel, I came across a problem where TTBCR is >> in improper state. If the bootloader uses the long descriptor format and jumps >> to kernel decompressor code, TTBCR may not be in the right state. So, as soon >> as the MMU is enabled, execution can not proceed further. >> >> Before enabling the MMU, it is required to clear the TTBCR.PD0 field to use >> TTBR0 for translation table walks. Also, TTBCR.N should be reset to '0' to >> indicate the correct base address width. The 'commit dbece45894d3a ("ARM: >> 7501/1: decompressor: reset ttbcr for VMSA ARMv7 cores")' does the reset of >> TTBCR.N, but doesn't consider all the bits for the size of TTBCR.N. >> >> when i tried the below change where i explicitly clear TTBCR.PD0 and use >> correct mask for TTBCR.N, I see proper memory after MMU is enabled and >> decompression succeeds. >> >> Request your comments on the change below. If it looks good, I can submit a >> patch for inclusion. >> >> ---------------------8<---------------------------------- >> diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S >> index af11c2f..5769f1f 100644 >> --- a/arch/arm/boot/compressed/head.S >> +++ b/arch/arm/boot/compressed/head.S >> @@ -779,7 +779,8 @@ __armv7_mmu_cache_on: >> orrne r0, r0, #1 @ MMU enabled >> movne r1, #0xfffffffd @ domain 0 = client >> bic r6, r6, #1 << 31 @ 32-bit translation system >> - bic r6, r6, #3 << 0 @ use only ttbr0 >> + bic r6, r6, #7 << 0 @ width of base address field >> + bic r6, r6, #1 << 4 @ use only ttbr0 > > You could combine those instructions like this: > > bic r6, r6, #(7 << 0) | (1 << 4) @ use only ttbr0 Sure, Thanks for the suggestion. I can incorporate this and submit a patch. Can i use your Acked-by? Thanks, -- Srinivas R > > Nicolas > -- > To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in > the body of a message to majordomo at vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc., is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.
next prev parent reply other threads:[~2016-09-10 5:50 UTC|newest] Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-09-09 16:34 Improper TTBCR for arm 32bit kernel decompression Srinivas Ramana 2016-09-09 16:34 ` Srinivas Ramana 2016-09-09 17:36 ` Nicolas Pitre 2016-09-09 17:36 ` Nicolas Pitre 2016-09-10 5:50 ` Srinivas Ramana [this message] 2016-09-10 5:50 ` Srinivas Ramana 2016-09-10 8:12 ` Srinivas Ramana 2016-09-10 8:12 ` Srinivas Ramana 2016-09-12 6:57 ` [PATCH] ARM: decompressor: reset ttbcr fields to use TTBR0 on ARMv7 Srinivas Ramana 2016-09-12 6:57 ` Srinivas Ramana 2016-09-12 10:23 ` Russell King - ARM Linux 2016-09-12 10:23 ` Russell King - ARM Linux 2016-09-12 17:51 ` Robin Murphy 2016-09-12 17:51 ` Robin Murphy 2016-09-13 14:52 ` Srinivas Ramana 2016-09-13 14:52 ` Srinivas Ramana 2016-09-27 12:16 ` Srinivas Ramana 2016-09-27 12:16 ` Srinivas Ramana 2016-09-27 12:54 ` Robin Murphy 2016-09-27 12:54 ` Robin Murphy 2016-09-28 12:45 ` [PATCH v1] " Srinivas Ramana 2016-09-28 12:45 ` Srinivas Ramana 2016-09-28 22:00 ` Russell King - ARM Linux 2016-09-28 22:00 ` Russell King - ARM Linux
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