diff options
| author | Dmitry Osipenko <digetx@gmail.com> | 2020-01-14 04:34:39 +0300 |
|---|---|---|
| committer | Wolfram Sang <wsa@the-dreams.de> | 2020-01-15 18:32:15 +0100 |
| commit | ae6028a65582118d8e8f5fa3c72524b44a878d1d (patch) | |
| tree | c3416effa6b86e1e55d4d32fc9dcd881e095324f | |
| parent | ede2299f7101a79fe8610ca0000734c9887ad4b2 (diff) | |
i2c: tegra: Rename I2C_PIO_MODE_MAX_LEN to I2C_PIO_MODE_PREFERRED_LEN
DMA is preferred for a larger transfers, while PIO is preferred for a
smaller transfers to avoid unnecessary DMA overhead. There is no strict
size limitations for the PIO-mode transfers, so let's rename the constant
for clarity.
Tested-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
| -rw-r--r-- | drivers/i2c/busses/i2c-tegra.c | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c index 0245fc2b5684..e0eb8f5dcd6b 100644 --- a/drivers/i2c/busses/i2c-tegra.c +++ b/drivers/i2c/busses/i2c-tegra.c @@ -131,11 +131,12 @@ #define I2C_PACKET_HEADER_SIZE 12 /* - * Upto I2C_PIO_MODE_MAX_LEN bytes, controller will use PIO mode, - * above this, controller will use DMA to fill FIFO. - * MAX PIO len is 20 bytes excluding packet header. + * I2C Controller will use PIO mode for transfers up to 32 bytes in order to + * avoid DMA overhead, otherwise external APB DMA controller will be used. + * Note that the actual MAX PIO length is 20 bytes because 32 bytes include + * I2C_PACKET_HEADER_SIZE. */ -#define I2C_PIO_MODE_MAX_LEN 32 +#define I2C_PIO_MODE_PREFERRED_LEN 32 /* * msg_end_type: The bus control which need to be send at end of transfer. @@ -1110,7 +1111,7 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev, xfer_size = msg->len + I2C_PACKET_HEADER_SIZE; xfer_size = ALIGN(xfer_size, BYTES_PER_FIFO_WORD); - i2c_dev->is_curr_dma_xfer = (xfer_size > I2C_PIO_MODE_MAX_LEN) && + i2c_dev->is_curr_dma_xfer = (xfer_size > I2C_PIO_MODE_PREFERRED_LEN) && i2c_dev->dma_buf && !i2c_dev->is_curr_atomic_xfer; tegra_i2c_config_fifo_trig(i2c_dev, xfer_size); |