spi_s3c24xx: add FIQ pseudo-DMA support

Add pseudo-DMA by FIQ to the S3C24XX SPI driver.  This allows the driver
to get DMA-like performance where there are either no free DMA channels or
when doing transfers that required both TX and RX data paths.

Since this patch requires the addition of an assembly file to hold the FIQ
code, we rename the module (instead of adding a rename of the .c file to
this patch).  We expect most users are loading this via udev and thus
there should be no change to the userland configuration.

Signed-off-by: Ben Dooks <ben@simtec.co.uk>
Signed-off-by: Simtec Linux Team <linux@simtec.co.uk>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

1 files changed, 116 insertions, 0 deletions

diff --git a/drivers/spi/spi_s3c24xx_fiq.S b/drivers/spi/spi_s3c24xx_fiq.S
new file mode 100644
index 000000000000..3793cae361db
--- /dev/null
+++ b/drivers/spi/spi_s3c24xx_fiq.S
@@ -0,0 +1,116 @@
+/* linux/drivers/spi/spi_s3c24xx_fiq.S
+ *
+ * Copyright 2009 Simtec Electronics
+ *      Ben Dooks <ben@simtec.co.uk>
+ *
+ * S3C24XX SPI - FIQ pseudo-DMA transfer code
+ *
+ * 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>
+
+#include <mach/map.h>
+#include <mach/regs-irq.h>
+#include <plat/regs-spi.h>
+
+#include "spi_s3c24xx_fiq.h"
+
+        .text
+
+        @ entry to these routines is as follows, with the register names
+        @ defined in fiq.h so that they can be shared with the C files which
+        @ setup the calling registers.
+        @
+        @ fiq_rirq      The base of the IRQ registers to find S3C2410_SRCPND
+        @ fiq_rtmp      Temporary register to hold tx/rx data
+        @ fiq_rspi      The base of the SPI register block
+        @ fiq_rtx       The tx buffer pointer
+        @ fiq_rrx       The rx buffer pointer
+        @ fiq_rcount    The number of bytes to move
+
+        @ each entry starts with a word entry of how long it is
+        @ and an offset to the irq acknowledgment word
+
+ENTRY(s3c24xx_spi_fiq_rx)
+s3c24xx_spi_fix_rx:
+        .word   fiq_rx_end - fiq_rx_start
+        .word   fiq_rx_irq_ack - fiq_rx_start
+fiq_rx_start:
+        ldr     fiq_rtmp, fiq_rx_irq_ack
+        str     fiq_rtmp, [ fiq_rirq, # S3C2410_SRCPND - S3C24XX_VA_IRQ ]
+
+        ldrb    fiq_rtmp, [ fiq_rspi, #  S3C2410_SPRDAT ]
+        strb    fiq_rtmp, [ fiq_rrx ], #1
+
+        mov     fiq_rtmp, #0xff
+        strb    fiq_rtmp, [ fiq_rspi, # S3C2410_SPTDAT ]
+
+        subs    fiq_rcount, fiq_rcount, #1
+        subnes  pc, lr, #4              @@ return, still have work to do
+
+        @@ set IRQ controller so that next op will trigger IRQ
+        mov     fiq_rtmp, #0
+        str     fiq_rtmp, [ fiq_rirq, # S3C2410_INTMOD  - S3C24XX_VA_IRQ ]
+        subs    pc, lr, #4
+
+fiq_rx_irq_ack:
+        .word   0
+fiq_rx_end:
+
+ENTRY(s3c24xx_spi_fiq_txrx)
+s3c24xx_spi_fiq_txrx:
+        .word   fiq_txrx_end - fiq_txrx_start
+        .word   fiq_txrx_irq_ack - fiq_txrx_start
+fiq_txrx_start:
+
+        ldrb    fiq_rtmp, [ fiq_rspi, #  S3C2410_SPRDAT ]
+        strb    fiq_rtmp, [ fiq_rrx ], #1
+
+        ldr     fiq_rtmp, fiq_txrx_irq_ack
+        str     fiq_rtmp, [ fiq_rirq, # S3C2410_SRCPND - S3C24XX_VA_IRQ ]
+
+        ldrb    fiq_rtmp, [ fiq_rtx ], #1
+        strb    fiq_rtmp, [ fiq_rspi, # S3C2410_SPTDAT ]
+
+        subs    fiq_rcount, fiq_rcount, #1
+        subnes  pc, lr, #4              @@ return, still have work to do
+
+        mov     fiq_rtmp, #0
+        str     fiq_rtmp, [ fiq_rirq, # S3C2410_INTMOD  - S3C24XX_VA_IRQ ]
+        subs    pc, lr, #4
+
+fiq_txrx_irq_ack:
+        .word   0
+
+fiq_txrx_end:
+
+ENTRY(s3c24xx_spi_fiq_tx)
+s3c24xx_spi_fix_tx:
+        .word   fiq_tx_end - fiq_tx_start
+        .word   fiq_tx_irq_ack - fiq_tx_start
+fiq_tx_start:
+        ldrb    fiq_rtmp, [ fiq_rspi, #  S3C2410_SPRDAT ]
+
+        ldr     fiq_rtmp, fiq_tx_irq_ack
+        str     fiq_rtmp, [ fiq_rirq, # S3C2410_SRCPND - S3C24XX_VA_IRQ ]
+
+        ldrb    fiq_rtmp, [ fiq_rtx ], #1
+        strb    fiq_rtmp, [ fiq_rspi, # S3C2410_SPTDAT ]
+
+        subs    fiq_rcount, fiq_rcount, #1
+        subnes  pc, lr, #4              @@ return, still have work to do
+
+        mov     fiq_rtmp, #0
+        str     fiq_rtmp, [ fiq_rirq, # S3C2410_INTMOD  - S3C24XX_VA_IRQ ]
+        subs    pc, lr, #4
+
+fiq_tx_irq_ack:
+        .word   0
+
+fiq_tx_end:
+
+        .end