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uboot-lantiq: danube: fix hanging lzma kernel uncompression 

At least since gcc 7.3.0 (OpenWrt 18.06) lwr/lwl are used in the
assembly of LzmaProps_Decode. While the decission made by the compiler
looks perfect fine, it triggers some obscure hang on lantiq danube-s
v1.5 with MX29LV640EB NOR flash chips.

Only if the offset 1 is used, the hang can be observed. Using any other
offset works fine:

  lwl s0,0(a1) - s0 == 0x6d000080
  lwl s0,1(a1) - hangs
  lwl s0,2(a1) - s0 == 0x0080xxxx
  lwl s0,3(a1) - s0 == 0x80xxxxxx

It isn't clear whether it is a limitation of the flash chip, the EBU or
something else.

Force 8bit reads to prevent gcc optimizing the read with lwr/lwl
instructions.

Signed-off-by: Mathias Kresin <dev@kresin.me>
This commit is contained in:
Mathias Kresin 2021-11-05 10:41:26 +01:00
parent 9bd9e04b6f
commit 565b62cca2
1 changed files with 48 additions and 0 deletions
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48
package/boot/uboot-lantiq/patches/0030-lzma-force-8bit-reads.patch Normal file
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@ -0,0 +1,48 @@
From a40a6e16ed76e5e26a0f60226b64c311d4a62c9f Mon Sep 17 00:00:00 2001
From: Mathias Kresin <dev@kresin.me>
Date: Sun, 31 Oct 2021 23:04:54 +0100
Subject: [PATCH] lzma: force 8bit reads
At least since gcc 7.3.0 (OpenWrt 18.06) lwr/lwl are used in the
assembly of LzmaProps_Decode. While the decission made by the compiler
looks perfect fine, it triggers some obscure hang on lantiq danube-s
v1.5 with MX29LV640EB NOR flash chips.
Only if the offset 1 is used, the hang can be observed. Using any other
offset works fine:
lwl s0,0(a1) - s0 == 0x6d000080
lwl s0,1(a1) - hangs
lwl s0,2(a1) - s0 == 0x0080xxxx
lwl s0,3(a1) - s0 == 0x80xxxxxx
It isn't clear whether it is a limitation of the flash chip, the EBU or
something else.
Force 8bit reads to prevent gcc optimizing the read with lwr/lwl
instructions.
Signed-off-by: Mathias Kresin <dev@kresin.me>
---
lib/lzma/LzmaDec.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/lib/lzma/LzmaDec.c
+++ b/lib/lzma/LzmaDec.c
@@ -7,6 +7,7 @@
#include "LzmaDec.h"
#include <linux/string.h>
+#include <asm/io.h>
#define kNumTopBits 24
#define kTopValue ((UInt32)1 << kNumTopBits)
@@ -929,7 +930,7 @@ SRes LzmaProps_Decode(CLzmaProps *p, con
if (size < LZMA_PROPS_SIZE)
return SZ_ERROR_UNSUPPORTED;
else
- dicSize = data[1] | ((UInt32)data[2] << 8) | ((UInt32)data[3] << 16) | ((UInt32)data[4] << 24);
+ dicSize = readb(&data[1]) | ((UInt32)readb(&data[2]) << 8) | ((UInt32)readb(&data[3]) << 16) | ((UInt32)readb(&data[4]) << 24);
if (dicSize < LZMA_DIC_MIN)
dicSize = LZMA_DIC_MIN;