> Yes. Most 64bit MIPS processors cannot access 64bit content > of registers when it is in 32bit mode. For clarity, there is no 32/64-bit mode in MIPS processors. There is a mode in which 64-bit OPERATIONS are enabled (that is, those instructions which operate on the full width of the registers) - See the definition of 64-bit Operations Enable in the MIPS64 Architecture for Programmers, volume III. Note that such operations are always enabled while the processor is running in Kernel Mode. The patch is a little short on context, but if you've got a 64-bit kernel, I had always assumed that save/restore of context is always done with LD/SD, not by figuring out whether a process has 64-bit operations enabled, then doing a conditional LD/SD or LW/SW. /gmu --- Michael Uhler, Chief Technology Officer MIPS Technologies, Inc. Email: uhler AT mips.com 1225 Charleston Road Voice: (650)567-5025 FAX: (650)567-5225 Mountain View, CA 94043 > -----Original Message----- > From: linux-mips-bounce@xxxxxxxxxxxxxx > [mailto:linux-mips-bounce@xxxxxxxxxxxxxx] On Behalf Of Fuxin Zhang > Sent: Wednesday, April 18, 2007 6:32 AM > To: Ralf Baechle > Cc: tiansm@xxxxxxxxxx; linux-mips@xxxxxxxxxxxxxx; Fuxin Zhang > Subject: Re: [PATCH 3/16] Kconfig update for lemote fulong mini-PC > > > >> + > >> > > > > Is there anything in implementation of this option > Loongson2-specific? > > > Yes. Most 64bit MIPS processors cannot access 64bit content > of registers when it is in 32bit mode. > > Loongson2 has no 32/64 mode bit in fact. > > And the usage arise from Loongson2's multimedia extension, > which is also uniq. > > If not then I suggest we make this option loook like: > > > > bool "Save 64bit integer registers" if > CPU_SUPPORTS_64BIT_KERNEL && > > 32BIT > > > > Somebody else might have a use for it! > > > > Ralf > > > > > > > > > > > >
