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ARM: riscpc: dma: improve address/length writing

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Rearrange writing the DMA addresses to generate more efficient code.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Russell King 2019-05-02 17:50:55 +01:00
parent 39694ed0db
commit e659587c64
1 changed files with 11 additions and 15 deletions
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26
arch/arm/mach-rpc/dma.c
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@ -100,7 +100,7 @@ static irqreturn_t iomd_dma_handle(int irq, void *dev_id)
struct iomd_dma *idma = dev_id;
unsigned long base = idma->base;
unsigned int state = idma->state;
unsigned int status;
unsigned int status, cur, end;
do {
status = iomd_readb(base + ST);
@ -110,21 +110,17 @@ static irqreturn_t iomd_dma_handle(int irq, void *dev_id)
if ((state ^ status) & DMA_ST_AB)
iomd_get_next_sg(idma);
switch (status & (DMA_ST_OFL | DMA_ST_AB)) {
case DMA_ST_OFL: /* OIA */
case DMA_ST_AB: /* .IB */
iomd_writel(idma->cur_addr, base + CURA);
iomd_writel(idma->cur_len, base + ENDA);
state = DMA_ST_AB;
break;
case DMA_ST_OFL | DMA_ST_AB: /* OIB */
case 0: /* .IA */
iomd_writel(idma->cur_addr, base + CURB);
iomd_writel(idma->cur_len, base + ENDB);
state = 0;
break;
// This efficiently implements state = OFL != AB ? AB : 0
state = ((status >> 2) ^ status) & DMA_ST_AB;
if (state) {
cur = CURA;
end = ENDA;
} else {
cur = CURB;
end = ENDB;
}
iomd_writel(idma->cur_addr, base + cur);
iomd_writel(idma->cur_len, base + end);
if (status & DMA_ST_OFL &&
idma->cur_len == (DMA_END_S|DMA_END_L))