linux/arch/arm/plat-mxc/ssi-fiq.S
Dave Martin 7095b95654 ARM: mxc: ssi-fiq: Make ssi-fiq.S Thumb-2 compatible
Because FIQ handlers get copied straight into the vectors page to
the FIQ vector entry point, FIQ handlers in a Thumb-2 kernel must
start in Thumb-2.  A Thumb-2 kernel enters all exception vectors in
Thumb-2.

This patch adapts the mxc SSI FIQ code suitable for a Thumb-2
kernel.

The code contained use of r13 (sp) which isn't allowed in Thumb-2.
r11 and r13 have been swapped throughout the file to work around
this.

Currently, the way that the function to be copied is located using
labels is a bit ugly: we cannot annotate the FIQ handler properly
as a Thumb-2 function, because this would set bit 0 of the label
address seen by the linker, causing off-by-one errors when copying
the function.  Ideally, the copy would be done with fncpy(), but
this would require changes to the common set_fiq_handler()
function.  For now, we don't touch this.

References to locally-defined global symbols with adr and ldr may
not be accepted by the assembler in Thumb-2.  Local shadow symbols
are added to work around this.

Signed-off-by: Dave Martin <dave.martin@linaro.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
2012-08-13 21:33:14 +02:00

148 lines
2.9 KiB
ArmAsm

/*
* Copyright (C) 2009 Sascha Hauer <s.hauer@pengutronix.de>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/linkage.h>
#include <asm/assembler.h>
/*
* r8 = bit 0-15: tx offset, bit 16-31: tx buffer size
* r9 = bit 0-15: rx offset, bit 16-31: rx buffer size
*/
#define SSI_STX0 0x00
#define SSI_SRX0 0x08
#define SSI_SISR 0x14
#define SSI_SIER 0x18
#define SSI_SACNT 0x38
#define SSI_SACNT_AC97EN (1 << 0)
#define SSI_SIER_TFE0_EN (1 << 0)
#define SSI_SISR_TFE0 (1 << 0)
#define SSI_SISR_RFF0 (1 << 2)
#define SSI_SIER_RFF0_EN (1 << 2)
.text
.global imx_ssi_fiq_start
.global imx_ssi_fiq_end
.global imx_ssi_fiq_base
.global imx_ssi_fiq_rx_buffer
.global imx_ssi_fiq_tx_buffer
/*
* imx_ssi_fiq_start is _intentionally_ not marked as a function symbol
* using ENDPROC(). imx_ssi_fiq_start and imx_ssi_fiq_end are used to
* mark the function body so that it can be copied to the FIQ vector in
* the vectors page. imx_ssi_fiq_start should only be called as the result
* of an FIQ: calling it directly will not work.
*/
imx_ssi_fiq_start:
ldr r12, .L_imx_ssi_fiq_base
/* TX */
ldr r13, .L_imx_ssi_fiq_tx_buffer
/* shall we send? */
ldr r11, [r12, #SSI_SIER]
tst r11, #SSI_SIER_TFE0_EN
beq 1f
/* TX FIFO empty? */
ldr r11, [r12, #SSI_SISR]
tst r11, #SSI_SISR_TFE0
beq 1f
mov r10, #0x10000
sub r10, #1
and r10, r10, r8 /* r10: current buffer offset */
add r13, r13, r10
ldrh r11, [r13]
strh r11, [r12, #SSI_STX0]
ldrh r11, [r13, #2]
strh r11, [r12, #SSI_STX0]
ldrh r11, [r13, #4]
strh r11, [r12, #SSI_STX0]
ldrh r11, [r13, #6]
strh r11, [r12, #SSI_STX0]
add r10, #8
lsr r11, r8, #16 /* r11: buffer size */
cmp r10, r11
lslgt r8, r11, #16
addle r8, #8
1:
/* RX */
/* shall we receive? */
ldr r11, [r12, #SSI_SIER]
tst r11, #SSI_SIER_RFF0_EN
beq 1f
/* RX FIFO full? */
ldr r11, [r12, #SSI_SISR]
tst r11, #SSI_SISR_RFF0
beq 1f
ldr r13, .L_imx_ssi_fiq_rx_buffer
mov r10, #0x10000
sub r10, #1
and r10, r10, r9 /* r10: current buffer offset */
add r13, r13, r10
ldr r11, [r12, #SSI_SACNT]
tst r11, #SSI_SACNT_AC97EN
ldr r11, [r12, #SSI_SRX0]
strh r11, [r13]
ldr r11, [r12, #SSI_SRX0]
strh r11, [r13, #2]
/* dummy read to skip slot 12 */
ldrne r11, [r12, #SSI_SRX0]
ldr r11, [r12, #SSI_SRX0]
strh r11, [r13, #4]
ldr r11, [r12, #SSI_SRX0]
strh r11, [r13, #6]
/* dummy read to skip slot 12 */
ldrne r11, [r12, #SSI_SRX0]
add r10, #8
lsr r11, r9, #16 /* r11: buffer size */
cmp r10, r11
lslgt r9, r11, #16
addle r9, #8
1:
@ return from FIQ
subs pc, lr, #4
.align
.L_imx_ssi_fiq_base:
imx_ssi_fiq_base:
.word 0x0
.L_imx_ssi_fiq_rx_buffer:
imx_ssi_fiq_rx_buffer:
.word 0x0
.L_imx_ssi_fiq_tx_buffer:
imx_ssi_fiq_tx_buffer:
.word 0x0
.L_imx_ssi_fiq_end:
imx_ssi_fiq_end: