From: Martin Sperl <ker...@martin.sperl.org>
Remove all limitations in can_dma that inhibit the use of DMA
To meet the limitiations of the HW we are now using the standardized
version of spi_translate_message, that:
* splits long transfers (> 60k)
* aligns transfers (on 4 byte boundary)
* merges transfers (for optimizations)
Signed-off-by: Martin Sperl <ker...@martin.sperl.org>
---
drivers/spi/spi-bcm2835.c | 58 +++++++++++++++------------------------------
1 file changed, 19 insertions(+), 39 deletions(-)
Changelog:
V1 -> V3: move to use spi-core methods where possible
diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c
index cf04960..75e4425 100644
--- a/drivers/spi/spi-bcm2835.c
+++ b/drivers/spi/spi-bcm2835.c
@@ -361,44 +361,8 @@ static bool bcm2835_spi_can_dma(struct spi_master *master,
if (!gpio_is_valid(spi->cs_gpio))
return false;
- /* we start DMA efforts only on bigger transfers */
- if (tfr->len < BCM2835_SPI_DMA_MIN_LENGTH)
- return false;
-
- /* BCM2835_SPI_DLEN has defined a max transfer size as
- * 16 bit, so max is 65535
- * we can revisit this by using an alternative transfer
- * method - ideally this would get done without any more
- * interaction...
- */
- if (tfr->len > 65535) {
- dev_warn_once(&spi->dev,
- "transfer size of %d too big for dma-transfer\n",
- tfr->len);
- return false;
- }
-
- /* if we run rx/tx_buf with word aligned addresses then we are OK */
- if ((((size_t)tfr->rx_buf & 3) == 0) &&
- (((size_t)tfr->tx_buf & 3) == 0))
- return true;
-
- /* otherwise we only allow transfers within the same page
- * to avoid wasting time on dma_mapping when it is not practical
- */
- if (((size_t)tfr->tx_buf & (PAGE_SIZE - 1)) + tfr->len > PAGE_SIZE) {
- dev_warn_once(&spi->dev,
- "Unaligned spi tx-transfer bridging page\n");
- return false;
- }
- if (((size_t)tfr->rx_buf & (PAGE_SIZE - 1)) + tfr->len > PAGE_SIZE) {
- dev_warn_once(&spi->dev,
- "Unaligned spi rx-transfer bridging page\n");
- return false;
- }
-
- /* return OK */
- return true;
+ /* use the default implementation */
+ return spi_can_dma_min_dma_len(master, spi, tfr);
}
static void bcm2835_dma_release(struct spi_master *master)
@@ -461,7 +425,23 @@ static void bcm2835_dma_init(struct spi_master *master,
struct device *dev)
/* all went well, so set can_dma */
master->can_dma = bcm2835_spi_can_dma;
- master->max_dma_len = 65535; /* limitation by BCM2835_SPI_DLEN */
+
+ /* set up transform message using the default implementation
+ * for size, alignment and merging transfers
+ */
+ master->translate_message = spi_translate_message_size_align_merge;
+
+ /* the minimum length when we run DMA */
+ master->min_dma_len = BCM2835_SPI_DMA_MIN_LENGTH;
+
+ /* the max_dma_len limited by BCM2835_SPI_DLEN is actually 65535,
+ * but for al practical purposes we use 15 pages (60k)
+ */
+ master->max_dma_len = 15 * PAGE_SIZE;
+
+ /* dma alignment is 4 bytes */
+ master->dma_alignment = 4;
+
/* need to do TX AND RX DMA, so we need dummy buffers */
master->flags = SPI_MASTER_MUST_RX | SPI_MASTER_MUST_TX;
--
1.7.10.4
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