| Message ID | 20220213151014.40548-1-andrei.lalaev@emlid.com |
|---|---|
| State | Deferred |
| Delegated to: | Tom Rini |
| Headers | show |
| Series | arm: sunxi: dram: restore previous value in DRAM | expand |
On 2/13/22 9:10 AM, Andrei Lalaev wrote: > It's better to restore previous value at offset because otherwise the > function can corrupt memory reserved by Linux (e.g. ramoops). With this patch, does ramoops work for you? and on which hardware? If so, I am definitely in favor of applying this patch. I'm a bit surprised that DRAM contents are maintained (this isn't the only place where they could be destroyed). I suppose the reset state of the PRCM enables pad hold, which would put the DRAM in self-refresh. So we just have to be careful during DRAM controller init. Regards, Samuel > Signed-off-by: Andrei Lalaev <andrei.lalaev@emlid.com> > --- > arch/arm/mach-sunxi/dram_helpers.c | 14 +++++++++++--- > 1 file changed, 11 insertions(+), 3 deletions(-) > > diff --git a/arch/arm/mach-sunxi/dram_helpers.c b/arch/arm/mach-sunxi/dram_helpers.c > index 2c873192e6..ed6db14f3c 100644 > --- a/arch/arm/mach-sunxi/dram_helpers.c > +++ b/arch/arm/mach-sunxi/dram_helpers.c > @@ -32,12 +32,20 @@ void mctl_await_completion(u32 *reg, u32 mask, u32 val) > #ifndef CONFIG_MACH_SUNIV > bool mctl_mem_matches(u32 offset) > { > + ulong addr = CONFIG_SYS_SDRAM_BASE + offset; > + u32 prev_val = readl(addr); > + bool ret = false; > + > /* Try to write different values to RAM at two addresses */ > writel(0, CONFIG_SYS_SDRAM_BASE); > - writel(0xaa55aa55, (ulong)CONFIG_SYS_SDRAM_BASE + offset); > + writel(0xaa55aa55, addr); > dsb(); > /* Check if the same value is actually observed when reading back */ > - return readl(CONFIG_SYS_SDRAM_BASE) == > - readl((ulong)CONFIG_SYS_SDRAM_BASE + offset); > + ret = readl(CONFIG_SYS_SDRAM_BASE) == readl(addr); > + > + /* Restore previous value */ > + writel(prev_val, addr); > + > + return ret; > } > #endif >
diff --git a/arch/arm/mach-sunxi/dram_helpers.c b/arch/arm/mach-sunxi/dram_helpers.c index 2c873192e6..ed6db14f3c 100644 --- a/arch/arm/mach-sunxi/dram_helpers.c +++ b/arch/arm/mach-sunxi/dram_helpers.c @@ -32,12 +32,20 @@ void mctl_await_completion(u32 *reg, u32 mask, u32 val) #ifndef CONFIG_MACH_SUNIV bool mctl_mem_matches(u32 offset) { + ulong addr = CONFIG_SYS_SDRAM_BASE + offset; + u32 prev_val = readl(addr); + bool ret = false; + /* Try to write different values to RAM at two addresses */ writel(0, CONFIG_SYS_SDRAM_BASE); - writel(0xaa55aa55, (ulong)CONFIG_SYS_SDRAM_BASE + offset); + writel(0xaa55aa55, addr); dsb(); /* Check if the same value is actually observed when reading back */ - return readl(CONFIG_SYS_SDRAM_BASE) == - readl((ulong)CONFIG_SYS_SDRAM_BASE + offset); + ret = readl(CONFIG_SYS_SDRAM_BASE) == readl(addr); + + /* Restore previous value */ + writel(prev_val, addr); + + return ret; } #endif
It's better to restore previous value at offset because otherwise the function can corrupt memory reserved by Linux (e.g. ramoops). Signed-off-by: Andrei Lalaev <andrei.lalaev@emlid.com> --- arch/arm/mach-sunxi/dram_helpers.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)