@@ -27,6 +27,7 @@
#define TRE_FLAGS_IEOT BIT(9)
#define TRE_FLAGS_BEI BIT(10)
#define TRE_FLAGS_LINK BIT(11)
+#define TRE_FLAGS_IMMEDIATE_DMA BIT(16)
#define TRE_FLAGS_TYPE GENMASK(23, 16)
/* SPI CONFIG0 WD0 */
@@ -64,6 +65,7 @@
/* DMA TRE */
#define TRE_DMA_LEN GENMASK(23, 0)
+#define TRE_DMA_IMMEDIATE_LEN GENMASK(3, 0)
/* Register offsets from gpi-top */
#define GPII_n_CH_k_CNTXT_0_OFFS(n, k) (0x20000 + (0x4000 * (n)) + (0x80 * (k)))
@@ -1711,6 +1713,8 @@ static int gpi_create_spi_tre(struct gchan *chan, struct gpi_desc *desc,
dma_addr_t address;
struct gpi_tre *tre;
unsigned int i;
+ u8 *buf;
+ int len = 0;
/* first create config tre if applicable */
if (direction == DMA_MEM_TO_DEV && spi->set_config) {
@@ -1763,14 +1767,32 @@ static int gpi_create_spi_tre(struct gchan *chan, struct gpi_desc *desc,
tre_idx++;
address = sg_dma_address(sgl);
- tre->dword[0] = lower_32_bits(address);
- tre->dword[1] = upper_32_bits(address);
+ len = sg_dma_len(sgl);
- tre->dword[2] = u32_encode_bits(sg_dma_len(sgl), TRE_DMA_LEN);
+ /* Support Immediate dma for write transfers for data length up to 8 bytes */
+ if ((spi->flags & QCOM_GPI_IMMEDIATE_DMA) && direction == DMA_MEM_TO_DEV) {
+ buf = (u8 *)sg_virt(sgl);
- tre->dword[3] = u32_encode_bits(TRE_TYPE_DMA, TRE_FLAGS_TYPE);
- if (direction == DMA_MEM_TO_DEV)
+ /* memcpy may not always be length of 8, hence pre-fill both dword's with 0 */
+ tre->dword[0] = 0;
+ tre->dword[1] = 0;
+ memcpy((u8 *)&tre->dword[0], buf, len);
+
+ tre->dword[2] = u32_encode_bits(len, TRE_DMA_IMMEDIATE_LEN);
+
+ tre->dword[3] = u32_encode_bits(TRE_TYPE_DMA, TRE_FLAGS_TYPE);
tre->dword[3] |= u32_encode_bits(1, TRE_FLAGS_IEOT);
+ tre->dword[3] |= u32_encode_bits(1, TRE_FLAGS_IMMEDIATE_DMA);
+ } else {
+ tre->dword[0] = lower_32_bits(address);
+ tre->dword[1] = upper_32_bits(address);
+
+ tre->dword[2] = u32_encode_bits(len, TRE_DMA_LEN);
+
+ tre->dword[3] = u32_encode_bits(TRE_TYPE_DMA, TRE_FLAGS_TYPE);
+ if (direction == DMA_MEM_TO_DEV)
+ tre->dword[3] |= u32_encode_bits(1, TRE_FLAGS_IEOT);
+ }
for (i = 0; i < tre_idx; i++)
dev_dbg(dev, "TRE:%d %x:%x:%x:%x\n", i, desc->tre[i].dword[0],
@@ -472,11 +472,18 @@ static int setup_gsi_xfer(struct spi_transfer *xfer, struct spi_geni_master *mas
mas->cur_speed_hz = xfer->speed_hz;
}
+ /*
+ * Set QCOM_GPI_IMMEDIATE_DMA flag if transfer length up to 8 bytes.
+ */
if (xfer->tx_buf && xfer->rx_buf) {
peripheral.cmd = SPI_DUPLEX;
+ if (xfer->len <= QCOM_GPI_IMMEDIATE_DMA_LEN)
+ peripheral.flags |= QCOM_GPI_IMMEDIATE_DMA;
} else if (xfer->tx_buf) {
peripheral.cmd = SPI_TX;
peripheral.rx_len = 0;
+ if (xfer->len <= QCOM_GPI_IMMEDIATE_DMA_LEN)
+ peripheral.flags |= QCOM_GPI_IMMEDIATE_DMA;
} else if (xfer->rx_buf) {
peripheral.cmd = SPI_RX;
if (!(mas->cur_bits_per_word % MIN_WORD_LEN)) {
@@ -15,6 +15,11 @@ enum spi_transfer_cmd {
SPI_DUPLEX,
};
+#define QCOM_GPI_BLOCK_EVENT_IRQ BIT(0)
+#define QCOM_GPI_IMMEDIATE_DMA BIT(1)
+
+#define QCOM_GPI_IMMEDIATE_DMA_LEN 8
+
/**
* struct gpi_spi_config - spi config for peripheral
*
@@ -30,6 +35,7 @@ enum spi_transfer_cmd {
* @cs: chip select toggle
* @set_config: set peripheral config
* @rx_len: receive length for buffer
+ * @flags: flags for immediate dma and block event interrupt support
*/
struct gpi_spi_config {
u8 set_config;
@@ -44,6 +50,7 @@ struct gpi_spi_config {
u32 clk_src;
enum spi_transfer_cmd cmd;
u32 rx_len;
+ u8 flags;
};
enum i2c_op {
The DMA TRE(Transfer ring element) buffer contains the DMA buffer address. Accessing data from this address can cause significant delays in SPI transfers, which can be mitigated to some extent by utilizing immediate DMA support. QCOM GPI DMA hardware supports an immediate DMA feature for data up to 8 bytes, storing the data directly in the DMA TRE buffer instead of the DMA buffer address. This enhancement enables faster SPI data transfers. This optimization reduces the average transfer time from 25 us to 16 us for a single SPI transfer of 8 bytes length, with a clock frequency of 50 MHz. Signed-off-by: Jyothi Kumar Seerapu <quic_jseerapu@quicinc.com> --- drivers/dma/qcom/gpi.c | 32 +++++++++++++++++++++++++++----- drivers/spi/spi-geni-qcom.c | 7 +++++++ include/linux/dma/qcom-gpi-dma.h | 7 +++++++ 3 files changed, 41 insertions(+), 5 deletions(-)