From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <3A4CC527.BF9431A7@mailbag.com> Date: Fri, 29 Dec 2000 11:08:55 -0600 From: Tim Montgomery MIME-Version: 1.0 To: linuxppc-dev , tjmontgo@mailbag.com Subject: 64 bit memory access Content-Type: text/plain; charset=us-ascii Sender: owner-linuxppc-dev@lists.linuxppc.org List-Id: Hello, I have a quandary. My platform is a PowerPC (MPC750) based embedded machine. I have a device (memory-mapped) that I need to access that lives on an internal peripheral bus but has the unfortunate constraint of allowing only 64bit-wide writes. Any write of a smaller width results in an exception generated by the memory controller. Drivers exist for this device for other, lesser OSs that use FP regs to write the 64bit quantity to the bus (using lfd and stfd). However, from what I gather, using the FP regs in kernel drivers under Linux kernel (2.4.0test12-based) seems to be a no-no. I am afraid I am at an impasse. I need to: 1.) figure out a way to perform a 64bit write via other means OR 2.) make sure I don't screw up user mode FP usage (potential consequence of dinking with FP while in the kernel?) Any suggestions/insight would be appreciated. Regards, Tim ** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/