Re: [U-Boot] [PATCH] sunxi: Fix buggy sun6i/sun8i DRAM size detection logic
Hi,
On 24-12-14 17:58, Siarhei Siamashka wrote:
After reboot, reset or even short power off, DRAM typically retains
the old stale data for some period of time (for this type of memory,
the bits of data are stored in slowly discharging capacitors).
The current sun6i/sun8i DRAM size detection logic, which is
inherited from the Allwinner code, relies on using a large magic
signature with the hope that it is unique enough and unlikely to
ever accidentally match this leftover garbage data in RAM. But
this approach is inherently unsafe, as can be demonstrated using
the following test program:
/* A testcase for reproducing the problem **/
#include stdlib.h
#include stdio.h
#include stdint.h
void main(int argc, char *argv[])
{
size_t size, i;
uint32_t *buf;
/* Allocate the buffer */
if (argc 2 || !(size = (size_t)atoi(argv[1]) * 1048576) ||
!(buf = malloc(size))) {
printf(Need buffer size in MiB as a cmdline argument\n);
exit(1);
}
/* Fill it with the Allwinner DRAM magic values */
for (i = 0; i size / 4; i++)
buf[i] = 0xaa55aa55 + ((uintptr_t)buf[i] / 4) % 64;
/* Try to reboot */
system(reboot);
/* And wait */
for (;;) {}
}
/***/
If this test program is run on the device (giving it a large
chunk of memory), then the DRAM size detection logic in u-boot
gets confused after reboot and fails to initialize DRAM properly.
A better approach is not to rely on luck and abstain from making
any assumptions about the properties of the leftover garbage
data in RAM. Instead just use a more reliable code for testing
whether two different addresses refer to the same memory location.
Signed-off-by: Siarhei Siamashka siarhei.siamas...@gmail.com
Thanks for the patch. I've run various tests and it works well,
queued up for merging in u-boot-sunxi/next .
Regards,
Hans
---
Done only very limited testing on MSI Primo81 tablet (Allwinner A31s),
which is currently a rather impractical device for doing any sun6i code
development due to having no access to the serial console, USB or other
convenient ways to interact with the device.
It might be a good idea to backup/restore the data in RAM when doing
this check in the code.
Using the standard u-boot 'get_ram_size' function could be also an
option to replace the loops and simplify the sun6i/sun8i dram code
in the future. The only inconvenience is that 'get_ram_size' returns
'size' instead of 'log2(size)'. This could be probably resolved by
introducing a new 'get_ram_size_log2' common function. But since
I don't have any Allwinner A23/A31 devboard for testing/debugging,
don't expect me to do this work any time soon, or ever at all.
arch/arm/cpu/armv7/sunxi/dram_sun6i.c | 1 -
arch/arm/cpu/armv7/sunxi/dram_sun8i.c | 1 -
arch/arm/include/asm/arch-sunxi/dram.h | 22 ++
3 files changed, 6 insertions(+), 18 deletions(-)
diff --git a/arch/arm/cpu/armv7/sunxi/dram_sun6i.c
b/arch/arm/cpu/armv7/sunxi/dram_sun6i.c
index 4675c48..4518b80 100644
--- a/arch/arm/cpu/armv7/sunxi/dram_sun6i.c
+++ b/arch/arm/cpu/armv7/sunxi/dram_sun6i.c
@@ -377,7 +377,6 @@ unsigned long sunxi_dram_init(void)
MCTL_CR_BANK(1) | MCTL_CR_RANK(1));
/* Detect and set page size */
- mctl_mem_fill();
for (columns = 7; columns 20; columns++) {
if (mctl_mem_matches(1 columns))
break;
diff --git a/arch/arm/cpu/armv7/sunxi/dram_sun8i.c
b/arch/arm/cpu/armv7/sunxi/dram_sun8i.c
index df9ff1f..ebba53b 100644
--- a/arch/arm/cpu/armv7/sunxi/dram_sun8i.c
+++ b/arch/arm/cpu/armv7/sunxi/dram_sun8i.c
@@ -289,7 +289,6 @@ unsigned long sunxi_dram_init(void)
writel(0x000310f4 | MCTL_CR_PAGE_SIZE(page_size),
mctl_com-cr);
setbits_le32(mctl_com-swonr, 0x0003);
- mctl_mem_fill();
for (rows = 11; rows 16; rows++) {
offset = 1 (rows + columns + bus);
if (mctl_mem_matches(offset))
diff --git a/arch/arm/include/asm/arch-sunxi/dram.h
b/arch/arm/include/asm/arch-sunxi/dram.h
index 8d78029..7ff43e6 100644
--- a/arch/arm/include/asm/arch-sunxi/dram.h
+++ b/arch/arm/include/asm/arch-sunxi/dram.h
@@ -24,8 +24,6 @@
#include asm/arch/dram_sun4i.h
#endif
-#define MCTL_MEM_FILL_MATCH_COUNT 64
-
unsigned long sunxi_dram_init(void);
/*
@@ -42,24 +40,16 @@ static inline void mctl_await_completion(u32 *reg, u32
mask, u32 val)
}
/*
- * Fill beginning of DRAM with random data for mctl_mem_matches()
- */
-static inline void mctl_mem_fill(void)
-{
- int i;
-
- for (i = 0; i MCTL_MEM_FILL_MATCH_COUNT; i++)
- writel(0xaa55aa55 + i, CONFIG_SYS_SDRAM_BASE + i * 4);
-}
-
-/*
* Test if memory at offset offset matches memory at begin of DRAM
*/
static inline bool mctl_mem_matches(u32 offset)
{
-
Re: [U-Boot] [PATCH] sunxi: Fix buggy sun6i/sun8i DRAM size detection logic
Hi,
On 25-12-14 03:07, Siarhei Siamashka wrote:
On Wed, 24 Dec 2014 19:39:33 +0200
Siarhei Siamashka siarhei.siamas...@gmail.com wrote:
On Wed, 24 Dec 2014 18:58:17 +0200
Siarhei Siamashka siarhei.siamas...@gmail.com wrote:
After reboot, reset or even short power off, DRAM typically retains
the old stale data for some period of time (for this type of memory,
the bits of data are stored in slowly discharging capacitors).
The current sun6i/sun8i DRAM size detection logic, which is
inherited from the Allwinner code, relies on using a large magic
signature with the hope that it is unique enough and unlikely to
ever accidentally match this leftover garbage data in RAM. But
this approach is inherently unsafe, as can be demonstrated using
the following test program:
/* A testcase for reproducing the problem **/
#include stdlib.h
#include stdio.h
#include stdint.h
void main(int argc, char *argv[])
{
size_t size, i;
uint32_t *buf;
/* Allocate the buffer */
if (argc 2 || !(size = (size_t)atoi(argv[1]) * 1048576) ||
!(buf = malloc(size))) {
printf(Need buffer size in MiB as a cmdline argument\n);
exit(1);
}
/* Fill it with the Allwinner DRAM magic values */
for (i = 0; i size / 4; i++)
buf[i] = 0xaa55aa55 + ((uintptr_t)buf[i] / 4) % 64;
/* Try to reboot */
system(reboot);
/* And wait */
for (;;) {}
}
/***/
If this test program is run on the device (giving it a large
chunk of memory), then the DRAM size detection logic in u-boot
gets confused after reboot and fails to initialize DRAM properly.
A better approach is not to rely on luck and abstain from making
any assumptions about the properties of the leftover garbage
data in RAM. Instead just use a more reliable code for testing
whether two different addresses refer to the same memory location.
Signed-off-by: Siarhei Siamashka siarhei.siamas...@gmail.com
Thanks for the patch, it looks good to me, I'll give it a test on my
own sun6i and sun8i boards when I find some time to do so.
---
Done only very limited testing on MSI Primo81 tablet (Allwinner A31s),
which is currently a rather impractical device for doing any sun6i code
development due to having no access to the serial console, USB or other
convenient ways to interact with the device.
Got a serial console on my tablet via a MicroSD breakout board. So I'm
retracting this statement :-)
Nice. Note that my personal u-boot git repo has lcd support in the sunxi-wip
branch, so that we can have at least u-boot output messages on tablets, but
I guess that FEL + console via microsd breakout works too.
If you can point me to a fex file for your board I can add a defconfig for
your tablet with hopefully working LCD support.
And indeed, the DRAM parameters get incorrectly detected after running
the test program (the system fails to boot later on):
Bummer, does this happen with both the old and the new memcmp functions ?
I'll send you a private mail with a statically linked util I've written
called mmio-dump, which can dump any hardware address from within android,
assuming you've an adb shell as root on your tablet, you can then copy
this to /system/bin and use it to dump the dram controller registers,
compare with what u-boot selects and see where we're getting things wrong.
Usage is e.g.:
mmio-dump 0x01c62000 64
U-Boot 2015.01-rc3-02809-g02f4a69-dirty (Dec 25 2014 - 03:05:03) Allwinner
Technology
CPU: Allwinner A31s (SUN6I)
I2C: ready
DRAM: 248 MiB
Using default environment
It might be a good idea to backup/restore the data in RAM when doing
this check in the code.
BTW, I only mentioned this because the 'get_ram_size' function restores
memory to the original state after it has done the job. But if being
non-destructive is not a requirement for the 'mctl_mem_matches'
function, then there is no need to care.
I don't think we care, at least not until we add support for coming out
of standby / self-refresh mode, and when we do we should have the
dram paras stored in SoC sram somewhere, and thus not use the detect
path at all.
Using the standard u-boot 'get_ram_size' function could be also an
option to replace the loops and simplify the sun6i/sun8i dram code
in the future. The only inconvenience is that 'get_ram_size' returns
'size' instead of 'log2(size)'. This could be probably resolved by
introducing a new 'get_ram_size_log2' common function.
Just noticed that there is actually '__ilog2' function in u-boot. This
makes it easier to switch the sun6i/sun8i dram code to using the
standard 'get_ram_size' function.
With the use of __ilog2(get_ram_size(...)), the DRAM parameters
detection may look like the piece of code below. But not sure if this
is actually any better than the use of 'mctl_mem_matches' at least on
sun6i hardware. Still on sun8i it fits quite fine.
On sun8i this seems to make sense, on sun6i I'm not
Re: [U-Boot] [PATCH] sunxi: Fix buggy sun6i/sun8i DRAM size detection logic
On Thu, 25 Dec 2014 11:14:23 +0100
Hans de Goede hdego...@redhat.com wrote:
Hi,
On 25-12-14 03:07, Siarhei Siamashka wrote:
On Wed, 24 Dec 2014 19:39:33 +0200
Siarhei Siamashka siarhei.siamas...@gmail.com wrote:
On Wed, 24 Dec 2014 18:58:17 +0200
Siarhei Siamashka siarhei.siamas...@gmail.com wrote:
After reboot, reset or even short power off, DRAM typically retains
the old stale data for some period of time (for this type of memory,
the bits of data are stored in slowly discharging capacitors).
The current sun6i/sun8i DRAM size detection logic, which is
inherited from the Allwinner code, relies on using a large magic
signature with the hope that it is unique enough and unlikely to
ever accidentally match this leftover garbage data in RAM. But
this approach is inherently unsafe, as can be demonstrated using
the following test program:
/* A testcase for reproducing the problem **/
#include stdlib.h
#include stdio.h
#include stdint.h
void main(int argc, char *argv[])
{
size_t size, i;
uint32_t *buf;
/* Allocate the buffer */
if (argc 2 || !(size = (size_t)atoi(argv[1]) * 1048576) ||
!(buf = malloc(size))) {
printf(Need buffer size in MiB as a cmdline argument\n);
exit(1);
}
/* Fill it with the Allwinner DRAM magic values */
for (i = 0; i size / 4; i++)
buf[i] = 0xaa55aa55 + ((uintptr_t)buf[i] / 4) % 64;
/* Try to reboot */
system(reboot);
/* And wait */
for (;;) {}
}
/***/
If this test program is run on the device (giving it a large
chunk of memory), then the DRAM size detection logic in u-boot
gets confused after reboot and fails to initialize DRAM properly.
A better approach is not to rely on luck and abstain from making
any assumptions about the properties of the leftover garbage
data in RAM. Instead just use a more reliable code for testing
whether two different addresses refer to the same memory location.
Signed-off-by: Siarhei Siamashka siarhei.siamas...@gmail.com
Thanks for the patch, it looks good to me, I'll give it a test on my
own sun6i and sun8i boards when I find some time to do so.
Thanks.
---
Done only very limited testing on MSI Primo81 tablet (Allwinner A31s),
which is currently a rather impractical device for doing any sun6i code
development due to having no access to the serial console, USB or other
convenient ways to interact with the device.
Got a serial console on my tablet via a MicroSD breakout board. So I'm
retracting this statement :-)
Nice. Note that my personal u-boot git repo has lcd support in the sunxi-wip
branch, so that we can have at least u-boot output messages on tablets, but
I guess that FEL + console via microsd breakout works too.
HDMI works too. Too bad that neither LCD nor HDMI can handle input. But
at least the UART console can. I was hoping to just get WLAN working as
the next step in order to use it instead of the UART console for
communicating with the device.
The MSI Primo81 is quite a nice tablet:
* has a HDMI connector (can run a real desktop Linux system on a HDMI
monitor, that is if we get USB OTG working)
* has access to the hardware FEL button (this makes the device truly
unbrickable)
* has a sturdy slim metal frame, but a downside is that it may be
more difficult/dangerous to disassemble
* has an IPS LCD display with good colors and viewing angles but
unfortunately relatively low resolution (1024x768)
* The current price seems to be around or under 100 EUR on amazon.de
and other places.
If you can point me to a fex file for your board I can add a defconfig for
your tablet with hopefully working LCD support.
If you really insist on doing this yourself, then you can find the fex
file in the sunxi-boards git repository:
https://github.com/linux-sunxi/sunxi-boards/blob/master/sys_config/a31s/msi_primo81.fex
In any case, this tablet is not going to be really usable until the
mainline kernel gets USB OTG support. Which gives us some weeks/months
to take care of the necessary dts/defconfig files.
And indeed, the DRAM parameters get incorrectly detected after running
the test program (the system fails to boot later on):
Bummer, does this happen with both the old and the new memcmp functions ?
Everything works fine after the sunxi: Fix buggy sun6i/sun8i DRAM size
detection logic patch is applied. Sorry for not stating this clearly
enough.
Without the patch and after running the test program, I just see that
the system fails to boot. Typically with the HDMI not coming up at all.
The UART console allows to see why it fails and makes debugging
possible.
I'll send you a private mail with a statically linked util I've written
called mmio-dump, which can dump any hardware address from within android,
assuming you've an adb shell as root on
Re: [U-Boot] [PATCH] sunxi: Fix buggy sun6i/sun8i DRAM size detection logic
Hi,
On 25-12-14 17:13, Siarhei Siamashka wrote:
On Thu, 25 Dec 2014 11:14:23 +0100
Hans de Goede hdego...@redhat.com wrote:
Hi,
On 25-12-14 03:07, Siarhei Siamashka wrote:
On Wed, 24 Dec 2014 19:39:33 +0200
Siarhei Siamashka siarhei.siamas...@gmail.com wrote:
On Wed, 24 Dec 2014 18:58:17 +0200
Siarhei Siamashka siarhei.siamas...@gmail.com wrote:
After reboot, reset or even short power off, DRAM typically retains
the old stale data for some period of time (for this type of memory,
the bits of data are stored in slowly discharging capacitors).
The current sun6i/sun8i DRAM size detection logic, which is
inherited from the Allwinner code, relies on using a large magic
signature with the hope that it is unique enough and unlikely to
ever accidentally match this leftover garbage data in RAM. But
this approach is inherently unsafe, as can be demonstrated using
the following test program:
/* A testcase for reproducing the problem **/
#include stdlib.h
#include stdio.h
#include stdint.h
void main(int argc, char *argv[])
{
size_t size, i;
uint32_t *buf;
/* Allocate the buffer */
if (argc 2 || !(size = (size_t)atoi(argv[1]) * 1048576) ||
!(buf = malloc(size))) {
printf(Need buffer size in MiB as a cmdline argument\n);
exit(1);
}
/* Fill it with the Allwinner DRAM magic values */
for (i = 0; i size / 4; i++)
buf[i] = 0xaa55aa55 + ((uintptr_t)buf[i] / 4) % 64;
/* Try to reboot */
system(reboot);
/* And wait */
for (;;) {}
}
/***/
If this test program is run on the device (giving it a large
chunk of memory), then the DRAM size detection logic in u-boot
gets confused after reboot and fails to initialize DRAM properly.
A better approach is not to rely on luck and abstain from making
any assumptions about the properties of the leftover garbage
data in RAM. Instead just use a more reliable code for testing
whether two different addresses refer to the same memory location.
Signed-off-by: Siarhei Siamashka siarhei.siamas...@gmail.com
Thanks for the patch, it looks good to me, I'll give it a test on my
own sun6i and sun8i boards when I find some time to do so.
Thanks.
---
Done only very limited testing on MSI Primo81 tablet (Allwinner A31s),
which is currently a rather impractical device for doing any sun6i code
development due to having no access to the serial console, USB or other
convenient ways to interact with the device.
Got a serial console on my tablet via a MicroSD breakout board. So I'm
retracting this statement :-)
Nice. Note that my personal u-boot git repo has lcd support in the sunxi-wip
branch, so that we can have at least u-boot output messages on tablets, but
I guess that FEL + console via microsd breakout works too.
HDMI works too. Too bad that neither LCD nor HDMI can handle input. But
at least the UART console can. I was hoping to just get WLAN working as
the next step in order to use it instead of the UART console for
communicating with the device.
The MSI Primo81 is quite a nice tablet:
* has a HDMI connector (can run a real desktop Linux system on a HDMI
monitor, that is if we get USB OTG working)
* has access to the hardware FEL button (this makes the device truly
unbrickable)
* has a sturdy slim metal frame, but a downside is that it may be
more difficult/dangerous to disassemble
* has an IPS LCD display with good colors and viewing angles but
unfortunately relatively low resolution (1024x768)
* The current price seems to be around or under 100 EUR on amazon.de
and other places.
If you can point me to a fex file for your board I can add a defconfig for
your tablet with hopefully working LCD support.
If you really insist on doing this yourself, then you can find the fex
file in the sunxi-boards git repository:
https://github.com/linux-sunxi/sunxi-boards/blob/master/sys_config/a31s/msi_primo81.fex
In any case, this tablet is not going to be really usable until the
mainline kernel gets USB OTG support. Which gives us some weeks/months
to take care of the necessary dts/defconfig files.
Ack, I offered to create the defconfig since the alternative was to
write a short howto on the VIDEO_LCD_MODE Kconfig, but since I've done
that now anyways I'll happily wait for you to provide a defconfig.
And indeed, the DRAM parameters get incorrectly detected after running
the test program (the system fails to boot later on):
Bummer, does this happen with both the old and the new memcmp functions ?
Everything works fine after the sunxi: Fix buggy sun6i/sun8i DRAM size
detection logic patch is applied. Sorry for not stating this clearly
enough.
Ah, ok, that is good to know.
Without the patch and after running the test program, I just see that
the system fails to boot. Typically with the HDMI not coming up at all.
The UART console allows to see why it fails and makes debugging
[U-Boot] [PATCH] sunxi: Fix buggy sun6i/sun8i DRAM size detection logic
After reboot, reset or even short power off, DRAM typically retains
the old stale data for some period of time (for this type of memory,
the bits of data are stored in slowly discharging capacitors).
The current sun6i/sun8i DRAM size detection logic, which is
inherited from the Allwinner code, relies on using a large magic
signature with the hope that it is unique enough and unlikely to
ever accidentally match this leftover garbage data in RAM. But
this approach is inherently unsafe, as can be demonstrated using
the following test program:
/* A testcase for reproducing the problem **/
#include stdlib.h
#include stdio.h
#include stdint.h
void main(int argc, char *argv[])
{
size_t size, i;
uint32_t *buf;
/* Allocate the buffer */
if (argc 2 || !(size = (size_t)atoi(argv[1]) * 1048576) ||
!(buf = malloc(size))) {
printf(Need buffer size in MiB as a cmdline argument\n);
exit(1);
}
/* Fill it with the Allwinner DRAM magic values */
for (i = 0; i size / 4; i++)
buf[i] = 0xaa55aa55 + ((uintptr_t)buf[i] / 4) % 64;
/* Try to reboot */
system(reboot);
/* And wait */
for (;;) {}
}
/***/
If this test program is run on the device (giving it a large
chunk of memory), then the DRAM size detection logic in u-boot
gets confused after reboot and fails to initialize DRAM properly.
A better approach is not to rely on luck and abstain from making
any assumptions about the properties of the leftover garbage
data in RAM. Instead just use a more reliable code for testing
whether two different addresses refer to the same memory location.
Signed-off-by: Siarhei Siamashka siarhei.siamas...@gmail.com
---
Done only very limited testing on MSI Primo81 tablet (Allwinner A31s),
which is currently a rather impractical device for doing any sun6i code
development due to having no access to the serial console, USB or other
convenient ways to interact with the device.
It might be a good idea to backup/restore the data in RAM when doing
this check in the code.
Using the standard u-boot 'get_ram_size' function could be also an
option to replace the loops and simplify the sun6i/sun8i dram code
in the future. The only inconvenience is that 'get_ram_size' returns
'size' instead of 'log2(size)'. This could be probably resolved by
introducing a new 'get_ram_size_log2' common function. But since
I don't have any Allwinner A23/A31 devboard for testing/debugging,
don't expect me to do this work any time soon, or ever at all.
arch/arm/cpu/armv7/sunxi/dram_sun6i.c | 1 -
arch/arm/cpu/armv7/sunxi/dram_sun8i.c | 1 -
arch/arm/include/asm/arch-sunxi/dram.h | 22 ++
3 files changed, 6 insertions(+), 18 deletions(-)
diff --git a/arch/arm/cpu/armv7/sunxi/dram_sun6i.c
b/arch/arm/cpu/armv7/sunxi/dram_sun6i.c
index 4675c48..4518b80 100644
--- a/arch/arm/cpu/armv7/sunxi/dram_sun6i.c
+++ b/arch/arm/cpu/armv7/sunxi/dram_sun6i.c
@@ -377,7 +377,6 @@ unsigned long sunxi_dram_init(void)
MCTL_CR_BANK(1) | MCTL_CR_RANK(1));
/* Detect and set page size */
- mctl_mem_fill();
for (columns = 7; columns 20; columns++) {
if (mctl_mem_matches(1 columns))
break;
diff --git a/arch/arm/cpu/armv7/sunxi/dram_sun8i.c
b/arch/arm/cpu/armv7/sunxi/dram_sun8i.c
index df9ff1f..ebba53b 100644
--- a/arch/arm/cpu/armv7/sunxi/dram_sun8i.c
+++ b/arch/arm/cpu/armv7/sunxi/dram_sun8i.c
@@ -289,7 +289,6 @@ unsigned long sunxi_dram_init(void)
writel(0x000310f4 | MCTL_CR_PAGE_SIZE(page_size),
mctl_com-cr);
setbits_le32(mctl_com-swonr, 0x0003);
- mctl_mem_fill();
for (rows = 11; rows 16; rows++) {
offset = 1 (rows + columns + bus);
if (mctl_mem_matches(offset))
diff --git a/arch/arm/include/asm/arch-sunxi/dram.h
b/arch/arm/include/asm/arch-sunxi/dram.h
index 8d78029..7ff43e6 100644
--- a/arch/arm/include/asm/arch-sunxi/dram.h
+++ b/arch/arm/include/asm/arch-sunxi/dram.h
@@ -24,8 +24,6 @@
#include asm/arch/dram_sun4i.h
#endif
-#define MCTL_MEM_FILL_MATCH_COUNT 64
-
unsigned long sunxi_dram_init(void);
/*
@@ -42,24 +40,16 @@ static inline void mctl_await_completion(u32 *reg, u32
mask, u32 val)
}
/*
- * Fill beginning of DRAM with random data for mctl_mem_matches()
- */
-static inline void mctl_mem_fill(void)
-{
- int i;
-
- for (i = 0; i MCTL_MEM_FILL_MATCH_COUNT; i++)
- writel(0xaa55aa55 + i, CONFIG_SYS_SDRAM_BASE + i * 4);
-}
-
-/*
* Test if memory at offset offset matches memory at begin of DRAM
*/
static inline bool mctl_mem_matches(u32 offset)
{
- return memcmp((u32 *)CONFIG_SYS_SDRAM_BASE,
- (u32 *)(CONFIG_SYS_SDRAM_BASE + offset),
- MCTL_MEM_FILL_MATCH_COUNT * 4) == 0;
+ /* Try to write different
Re: [U-Boot] [PATCH] sunxi: Fix buggy sun6i/sun8i DRAM size detection logic
On Wed, 24 Dec 2014 18:58:17 +0200
Siarhei Siamashka siarhei.siamas...@gmail.com wrote:
After reboot, reset or even short power off, DRAM typically retains
the old stale data for some period of time (for this type of memory,
the bits of data are stored in slowly discharging capacitors).
The current sun6i/sun8i DRAM size detection logic, which is
inherited from the Allwinner code, relies on using a large magic
signature with the hope that it is unique enough and unlikely to
ever accidentally match this leftover garbage data in RAM. But
this approach is inherently unsafe, as can be demonstrated using
the following test program:
/* A testcase for reproducing the problem **/
#include stdlib.h
#include stdio.h
#include stdint.h
void main(int argc, char *argv[])
{
size_t size, i;
uint32_t *buf;
/* Allocate the buffer */
if (argc 2 || !(size = (size_t)atoi(argv[1]) * 1048576) ||
!(buf = malloc(size))) {
printf(Need buffer size in MiB as a cmdline argument\n);
exit(1);
}
/* Fill it with the Allwinner DRAM magic values */
for (i = 0; i size / 4; i++)
buf[i] = 0xaa55aa55 + ((uintptr_t)buf[i] / 4) % 64;
/* Try to reboot */
system(reboot);
/* And wait */
for (;;) {}
}
/***/
If this test program is run on the device (giving it a large
chunk of memory), then the DRAM size detection logic in u-boot
gets confused after reboot and fails to initialize DRAM properly.
A better approach is not to rely on luck and abstain from making
any assumptions about the properties of the leftover garbage
data in RAM. Instead just use a more reliable code for testing
whether two different addresses refer to the same memory location.
Signed-off-by: Siarhei Siamashka siarhei.siamas...@gmail.com
---
Done only very limited testing on MSI Primo81 tablet (Allwinner A31s),
which is currently a rather impractical device for doing any sun6i code
development due to having no access to the serial console, USB or other
convenient ways to interact with the device.
It might be a good idea to backup/restore the data in RAM when doing
this check in the code.
Using the standard u-boot 'get_ram_size' function could be also an
option to replace the loops and simplify the sun6i/sun8i dram code
in the future. The only inconvenience is that 'get_ram_size' returns
'size' instead of 'log2(size)'. This could be probably resolved by
introducing a new 'get_ram_size_log2' common function.
Just noticed that there is actually '__ilog2' function in u-boot. This
makes it easier to switch the sun6i/sun8i dram code to using the
standard 'get_ram_size' function.
--
Best regards,
Siarhei Siamashka
___
U-Boot mailing list
U-Boot@lists.denx.de
http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] [PATCH] sunxi: Fix buggy sun6i/sun8i DRAM size detection logic
On Wed, 24 Dec 2014 19:39:33 +0200
Siarhei Siamashka siarhei.siamas...@gmail.com wrote:
On Wed, 24 Dec 2014 18:58:17 +0200
Siarhei Siamashka siarhei.siamas...@gmail.com wrote:
After reboot, reset or even short power off, DRAM typically retains
the old stale data for some period of time (for this type of memory,
the bits of data are stored in slowly discharging capacitors).
The current sun6i/sun8i DRAM size detection logic, which is
inherited from the Allwinner code, relies on using a large magic
signature with the hope that it is unique enough and unlikely to
ever accidentally match this leftover garbage data in RAM. But
this approach is inherently unsafe, as can be demonstrated using
the following test program:
/* A testcase for reproducing the problem **/
#include stdlib.h
#include stdio.h
#include stdint.h
void main(int argc, char *argv[])
{
size_t size, i;
uint32_t *buf;
/* Allocate the buffer */
if (argc 2 || !(size = (size_t)atoi(argv[1]) * 1048576) ||
!(buf = malloc(size))) {
printf(Need buffer size in MiB as a cmdline argument\n);
exit(1);
}
/* Fill it with the Allwinner DRAM magic values */
for (i = 0; i size / 4; i++)
buf[i] = 0xaa55aa55 + ((uintptr_t)buf[i] / 4) % 64;
/* Try to reboot */
system(reboot);
/* And wait */
for (;;) {}
}
/***/
If this test program is run on the device (giving it a large
chunk of memory), then the DRAM size detection logic in u-boot
gets confused after reboot and fails to initialize DRAM properly.
A better approach is not to rely on luck and abstain from making
any assumptions about the properties of the leftover garbage
data in RAM. Instead just use a more reliable code for testing
whether two different addresses refer to the same memory location.
Signed-off-by: Siarhei Siamashka siarhei.siamas...@gmail.com
---
Done only very limited testing on MSI Primo81 tablet (Allwinner A31s),
which is currently a rather impractical device for doing any sun6i code
development due to having no access to the serial console, USB or other
convenient ways to interact with the device.
Got a serial console on my tablet via a MicroSD breakout board. So I'm
retracting this statement :-)
And indeed, the DRAM parameters get incorrectly detected after running
the test program (the system fails to boot later on):
U-Boot 2015.01-rc3-02809-g02f4a69-dirty (Dec 25 2014 - 03:05:03) Allwinner
Technology
CPU: Allwinner A31s (SUN6I)
I2C: ready
DRAM: 248 MiB
Using default environment
It might be a good idea to backup/restore the data in RAM when doing
this check in the code.
BTW, I only mentioned this because the 'get_ram_size' function restores
memory to the original state after it has done the job. But if being
non-destructive is not a requirement for the 'mctl_mem_matches'
function, then there is no need to care.
Using the standard u-boot 'get_ram_size' function could be also an
option to replace the loops and simplify the sun6i/sun8i dram code
in the future. The only inconvenience is that 'get_ram_size' returns
'size' instead of 'log2(size)'. This could be probably resolved by
introducing a new 'get_ram_size_log2' common function.
Just noticed that there is actually '__ilog2' function in u-boot. This
makes it easier to switch the sun6i/sun8i dram code to using the
standard 'get_ram_size' function.
With the use of __ilog2(get_ram_size(...)), the DRAM parameters
detection may look like the piece of code below. But not sure if this
is actually any better than the use of 'mctl_mem_matches' at least on
sun6i hardware. Still on sun8i it fits quite fine.
diff --git a/arch/arm/cpu/armv7/sunxi/dram_sun6i.c
b/arch/arm/cpu/armv7/sunxi/dram_sun6i.c
index 4675c48..139944d 100644
--- a/arch/arm/cpu/armv7/sunxi/dram_sun6i.c
+++ b/arch/arm/cpu/armv7/sunxi/dram_sun6i.c
@@ -332,6 +332,7 @@ unsigned long sunxi_dram_init(void)
(struct sunxi_mctl_com_reg *)SUNXI_DRAM_COM_BASE;
u32 offset;
int bank, bus, columns;
+ int n_col, n_row, n_bnk;
/* Set initial parameters, these get modified by the autodetect code */
struct dram_sun6i_para para = {
@@ -384,6 +385,10 @@ unsigned long sunxi_dram_init(void)
}
bus = (para.bus_width == 32) ? 2 : 1;
columns -= bus;
+
+ n_col = __ilog2(get_ram_size((long *)PHYS_SDRAM_0, PHYS_SDRAM_0_SIZE)) -
+ bus;
+
para.page_size = (1 columns) * (bus 1);
clrsetbits_le32(mctl_com-cr, MCTL_CR_PAGE_SIZE_MASK,
MCTL_CR_PAGE_SIZE(para.page_size));
@@ -394,6 +399,10 @@ unsigned long sunxi_dram_init(void)
if (mctl_mem_matches(offset))
break;
}
+
+ n_row = __ilog2(get_ram_size((long *)PHYS_SDRAM_0, PHYS_SDRAM_0_SIZE)) -
+
