/*
* Do a dcache operation by virtual address. This is useful for
* maintaining coherency in drivers which do DMA transfers and only need to
* perform cache maintenance on a particular memory range rather than the
* entire cache.
*/
static void dcache_op_va(void const *addr, size_t len, enum dcache_op op)
{
unsigned long line, linesize;
linesize = dcache_line_bytes();
line = (uintptr_t)addr & ~(linesize - 1);
dsb();
while (line < (uintptr_t)addr + len) {
switch(op) {
case OP_DCCIVAC:
dccivac(line);
break;
case OP_DCCVAC:
dccvac(line);
break;
case OP_DCIVAC:
dcivac(line);
break;
default:
break;
}
line += linesize;
}
isb();
}
/*
* xfer_setup() prepares a transfer. It does sanity checking, alignment, and
* sets transfer mode used by this channel (if not set already).
*
* A few caveats to watch out for:
* - The number of bytes which can be transferred may be smaller than the
* number of bytes the caller specifies. The number of bytes ready for
* a transfer will be returned (unless an error occurs).
*
* - Only one mode can be used for both RX and TX. The transfer mode of the
* SPI channel (spi->xfer_mode) is checked each time this function is called.
* If conflicting modes are detected, spi->xfer_mode will be set to
* XFER_MODE_NONE and an error will be returned.
*
* Returns bytes ready for transfer if successful, <0 to indicate error.
*/
static int xfer_setup(struct tegra_spi_channel *spi, void *buf,
unsigned int bytes, enum spi_direction dir)
{
unsigned int line_size = dcache_line_bytes();
unsigned int align;
int ret = -1;
if (!bytes)
return 0;
if (dir == SPI_SEND)
spi->out_buf = buf;
else if (dir == SPI_RECEIVE)
spi->in_buf = buf;
/*
* Alignment consideratons:
* When we enable caching we'll need to clean/invalidate portions of
* memory. So we need to be careful about memory alignment. Also, DMA
* likes to operate on 4-bytes at a time on the AHB side. So for
* example, if we only want to receive 1 byte, 4 bytes will be be
* written in memory even if those extra 3 bytes are beyond the length
* we want.
*
* For now we'll use PIO to send/receive unaligned bytes. We may
* consider setting aside some space for a kind of bounce buffer to
* stay in DMA mode once we have a chance to benchmark the two
* approaches.
*/
if (bytes < line_size) {
if (spi->xfer_mode == XFER_MODE_DMA) {
spi->xfer_mode = XFER_MODE_NONE;
ret = -1;
} else {
spi->xfer_mode = XFER_MODE_PIO;
ret = tegra_spi_pio_prepare(spi, bytes, dir);
}
goto done;
}
/* transfer bytes before the aligned boundary */
align = line_size - ((uintptr_t)buf % line_size);
if ((align != 0) && (align != line_size)) {
if (spi->xfer_mode == XFER_MODE_DMA) {
spi->xfer_mode = XFER_MODE_NONE;
ret = -1;
} else {
spi->xfer_mode = XFER_MODE_PIO;
ret = tegra_spi_pio_prepare(spi, align, dir);
}
goto done;
}
/* do aligned DMA transfer */
align = (((uintptr_t)buf + bytes) % line_size);
if (bytes - align > 0) {
unsigned int dma_bytes = bytes - align;
if (spi->xfer_mode == XFER_MODE_PIO) {
spi->xfer_mode = XFER_MODE_NONE;
ret = -1;
} else {
spi->xfer_mode = XFER_MODE_DMA;
ret = tegra_spi_dma_prepare(spi, dma_bytes, dir);
}
goto done;
}
/* transfer any remaining unaligned bytes */
if (align) {
if (spi->xfer_mode == XFER_MODE_DMA) {
spi->xfer_mode = XFER_MODE_NONE;
ret = -1;
} else {
spi->xfer_mode = XFER_MODE_PIO;
ret = tegra_spi_pio_prepare(spi, align, dir);
}
goto done;
}
done:
return ret;
}