Hi! On Fri, Feb 11, 2022 at 8:14 AM Chuanhong Guo <gch981213@xxxxxxxxx> wrote: > > It's reported that current memory detection code occasionally detects > larger memory under some bootloaders. > Current memory detection code tests whether address space wraps around > on KSEG0, which is unreliable because it's cached. > > Rewrite memory size detection to perform the same test on KSEG1 instead. > While at it, this patch also does the following two things: > 1. use a fixed pattern instead of a random function pointer as the magic > value. > 2. add an additional memory write and a second comparison as part of the > test to prevent possible smaller memory detection result due to > leftover values in memory. > > Fixes: 139c949f7f0a MIPS: ("ralink: mt7621: add memory detection support") I misplaced a bracket in this Fixes tag. > Reported-by: Rui Salvaterra <rsalvaterra@xxxxxxxxx> > Signed-off-by: Chuanhong Guo <gch981213@xxxxxxxxx> > --- > arch/mips/ralink/mt7621.c | 36 +++++++++++++++++++++++------------- > 1 file changed, 23 insertions(+), 13 deletions(-) > > diff --git a/arch/mips/ralink/mt7621.c b/arch/mips/ralink/mt7621.c > index d6efffd4dd20..12c8808e0dea 100644 > --- a/arch/mips/ralink/mt7621.c > +++ b/arch/mips/ralink/mt7621.c > @@ -22,7 +22,9 @@ > > #include "common.h" > > -static void *detect_magic __initdata = detect_memory_region; > +#define MT7621_MEM_TEST_PATTERN 0xaa5555aa > + > +static u32 detect_magic __initdata; > > int pcibios_root_bridge_prepare(struct pci_host_bridge *bridge) > { > @@ -58,24 +60,32 @@ phys_addr_t mips_cpc_default_phys_base(void) > panic("Cannot detect cpc address"); > } > > +static bool __init mt7621_addr_wraparound_test(phys_addr_t size) > +{ > + void *dm = (void *)KSEG1ADDR(&detect_magic); > + > + if (CPHYSADDR(dm + size) >= MT7621_LOWMEM_MAX_SIZE) > + return true; > + __raw_writel(MT7621_MEM_TEST_PATTERN, dm); > + if (__raw_readl(dm) != __raw_readl(dm + size)) > + return false; > + __raw_writel(!MT7621_MEM_TEST_PATTERN, dm); Someone on Github notified me that this second test pattern is incorrect. I actually mean to use ~MT7621_MEM_TEST_PATTERN here. I'll send a v2 fixing both issues. -- Regards, Chuanhong Guo