MIPS: math-emu: Add FP emu debugfs clear functionality

Add capability for the user to clear all FP emu debugfs counters.

This is achieved by having a special debugfs file "fpuemustats_clear"
(under default location "/sys/kernel/debug/mips"). Each access to the
file results in setting all counters to zero (it is enough, let's say,
to issue a "cat /sys/kernel/debug/mips/fpuemustats_clear").

This functionality already exists for R2 emulation statistics,
but was missing for FP emulation statistics. The implementation in
this patch is consistent with its R2 emulation counterpart.

Signed-off-by: Miodrag Dinic <miodrag.dinic@imgtec.com>
Signed-off-by: Goran Ferenc <goran.ferenc@imgtec.com>
Signed-off-by: Aleksandar Markovic <aleksandar.markovic@imgtec.com>
Cc: Douglas Leung <douglas.leung@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: Petar Jovanovic <petar.jovanovic@imgtec.com>
Cc: Raghu Gandham <raghu.gandham@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/17144/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/math-emu/me-debugfs.c

@@ -28,15 +28,51 @@ static int fpuemu_stat_get(void *data, u64 *val)
 }
 DEFINE_SIMPLE_ATTRIBUTE(fops_fpuemu_stat, fpuemu_stat_get, NULL, "%llu\n");
 
+static int fpuemustats_clear_show(struct seq_file *s, void *unused)
+{
+	__this_cpu_write((fpuemustats).emulated, 0);
+	__this_cpu_write((fpuemustats).loads, 0);
+	__this_cpu_write((fpuemustats).stores, 0);
+	__this_cpu_write((fpuemustats).branches, 0);
+	__this_cpu_write((fpuemustats).cp1ops, 0);
+	__this_cpu_write((fpuemustats).cp1xops, 0);
+	__this_cpu_write((fpuemustats).errors, 0);
+	__this_cpu_write((fpuemustats).ieee754_inexact, 0);
+	__this_cpu_write((fpuemustats).ieee754_underflow, 0);
+	__this_cpu_write((fpuemustats).ieee754_overflow, 0);
+	__this_cpu_write((fpuemustats).ieee754_zerodiv, 0);
+	__this_cpu_write((fpuemustats).ieee754_invalidop, 0);
+	__this_cpu_write((fpuemustats).ds_emul, 0);
+
+	return 0;
+}
+
+static int fpuemustats_clear_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, fpuemustats_clear_show, inode->i_private);
+}
+
+static const struct file_operations fpuemustats_clear_fops = {
+	.open                   = fpuemustats_clear_open,
+	.read			= seq_read,
+	.llseek			= seq_lseek,
+	.release		= single_release,
+};
+
 static int __init debugfs_fpuemu(void)
 {
-	struct dentry *d, *dir;
+	struct dentry *d, *dir, *reset_file;
 
 	if (!mips_debugfs_dir)
 		return -ENODEV;
 	dir = debugfs_create_dir("fpuemustats", mips_debugfs_dir);
 	if (!dir)
 		return -ENOMEM;
+	reset_file = debugfs_create_file("fpuemustats_clear", 0444,
+					 mips_debugfs_dir, NULL,
+					 &fpuemustats_clear_fops);
+	if (!reset_file)
+		return -ENOMEM;
 
 #define FPU_EMU_STAT_OFFSET(m)						\
 	offsetof(struct mips_fpu_emulator_stats, m)