kern/amd64: isa: Add minimal i8254 driver

Signed-off-by: Ian Moffett <ian@osmora.org>

2 files changed, 137 insertions, 0 deletions

diff --git a/sys/arch/amd64/isa/i8254.S b/sys/arch/amd64/isa/i8254.S
new file mode 100644
index 0000000..7efd3cf
--- /dev/null
+++ b/sys/arch/amd64/isa/i8254.S
@@ -0,0 +1,90 @@
+/*
+ * Copyright (c) 2025 Ian Marco Moffett and the Osmora Team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Hyra nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+    .set I8254_COMMAND,   0x43
+    .set I8254_CHANNEL0,  0x40
+
+    .text
+    .globl i8254_set_count
+i8254_set_count:
+    /*
+     * RDI: Count
+     */
+
+    push %r12
+    push %r13
+    push %r14
+    push %r15
+    push %rbx
+    push %rbp
+
+    mov %rdi, %rax              /* Count -> RAX */
+    mov $0x34, %al              /* Latch lo/hi bytes */
+    out %al, $I8254_COMMAND     /* Send the command */
+    out %al, $I8254_CHANNEL0    /* Write low byte */
+    shr $8, %ah                 /* Shift down, get high byte */
+    out %al, $I8254_CHANNEL0    /* Write high byte */
+
+    pop %rbp
+    pop %rbx
+    pop %r15
+    pop %r14
+    pop %r13
+    pop %r12
+    retq
+
+    .globl i8254_get_count
+i8254_get_count:
+    push %r12
+    push %r13
+    push %r14
+    push %r15
+    push %rbx
+    push %rbp
+
+    mov $0x00, %al              /* Get the current counter */
+    out %al, $I8254_COMMAND     /* Send the command */
+    xor %rdx, %rdx              /* Make sure RDX is zeroed */
+    in $I8254_CHANNEL0, %al     /* Read low byte */
+    mov %al, %dl                /* Set low byte */
+    in $I8254_CHANNEL0, %al     /* Read high byte */
+    shl $8, %dh                 /* Shift to make room */
+    or %al, %dl                 /* Merge high and low */
+    mov %rdx, %rax              /* Return what we got */
+
+    pop %rbp
+    pop %rbx
+    pop %r15
+    pop %r14
+    pop %r13
+    pop %r12
+    retq
+
+/* vim: ft=gas :
+*/
diff --git a/sys/inc/arch/amd64/i8254.h b/sys/inc/arch/amd64/i8254.h
new file mode 100644
index 0000000..c747d66
--- /dev/null
+++ b/sys/inc/arch/amd64/i8254.h
@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2025 Ian Marco Moffett and the Osmora Team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Hyra nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _MACHINE_I8254_H_
+#define _MACHINE_I8254_H_
+
+#include <sys/types.h>
+
+/*
+ * Set the current counter value of the i8254
+ * main channel
+ */
+void i8254_set_count(uint16_t count);
+
+/*
+ * Get the current count from the i8254 main
+ * channel
+ */
+uint16_t i8254_get_count(void);
+
+#endif  /* !_MACHINE_I8254_H_ */