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SubjectRe: [PATCH V3 3/3] i2c: tegra: Add DMA Support
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Date
26.01.2019 6:57, Sowjanya Komatineni пишет:
> This patch adds DMA support for Tegra I2C.
>
> Tegra I2C TX and RX FIFO depth is 8 words. PIO mode is used for
> transfer size of the max FIFO depth and DMA mode is used for
> transfer size higher than max FIFO depth to save CPU overhead.
>
> PIO mode needs full intervention of CPU to fill or empty FIFO's
> and also need to service multiple data requests interrupt for the
> same transaction adding overhead on CPU for large transfers.
>
> DMA mode is helpful for Large transfers during downloading or
> uploading FW over I2C to some external devices.
>
> Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
>
> ---
> [V3] : Updated without additional buffer allocation.
> [V2] : Updated based on V1 review feedback along with code cleanup for
> proper implementation of DMA.
>
> drivers/i2c/busses/i2c-tegra.c | 341 ++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 316 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index 3dcbc9960d9d..452358a77400 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -8,6 +8,9 @@
>
> #include <linux/clk.h>
> #include <linux/delay.h>
> +#include <linux/dmaengine.h>
> +#include <linux/dmapool.h>
> +#include <linux/dma-mapping.h>
> #include <linux/err.h>
> #include <linux/i2c.h>
> #include <linux/init.h>
> @@ -45,6 +48,8 @@
> #define I2C_FIFO_CONTROL_RX_FLUSH BIT(0)
> #define I2C_FIFO_CONTROL_TX_TRIG_SHIFT 5
> #define I2C_FIFO_CONTROL_RX_TRIG_SHIFT 2
> +#define I2C_FIFO_CONTROL_TX_TRIG(x) (((x) - 1) << 5)
> +#define I2C_FIFO_CONTROL_RX_TRIG(x) (((x) - 1) << 2)
> #define I2C_FIFO_STATUS 0x060
> #define I2C_FIFO_STATUS_TX_MASK 0xF0
> #define I2C_FIFO_STATUS_TX_SHIFT 4
> @@ -119,6 +124,16 @@
> /* Packet header size in bytes */
> #define I2C_PACKET_HEADER_SIZE 12
>
> +#define DATA_DMA_DIR_TX (1 << 0)
> +#define DATA_DMA_DIR_RX (1 << 1)
> +
> +/*
> + * 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.
> + */
> +#define I2C_PIO_MODE_MAX_LEN 20
> +
> /*
> * msg_end_type: The bus control which need to be send at end of transfer.
> * @MSG_END_STOP: Send stop pulse at end of transfer.
> @@ -179,6 +194,7 @@ struct tegra_i2c_hw_feature {
> * @fast_clk: clock reference for fast clock of I2C controller
> * @rst: reset control for the I2C controller
> * @base: ioremapped registers cookie
> + * @phys_addr: Physical address of I2C base address to use for DMA configuration
> * @cont_id: I2C controller ID, used for packet header
> * @irq: IRQ number of transfer complete interrupt
> * @irq_disabled: used to track whether or not the interrupt is enabled
> @@ -192,6 +208,14 @@ struct tegra_i2c_hw_feature {
> * @clk_divisor_non_hs_mode: clock divider for non-high-speed modes
> * @is_multimaster_mode: track if I2C controller is in multi-master mode
> * @xfer_lock: lock to serialize transfer submission and processing
> + * @has_dma: indicated if controller supports DMA
> + * @tx_dma_chan: DMA transmit channel
> + * @rx_dma_chan: DMA receive channel
> + * @dma_phys: handle to DMA resources
> + * @dma_buf: pointer to allocated DMA buffer
> + * @dma_buf_size: DMA buffer size
> + * @is_curr_dma_xfer: indicates active DMA transfer
> + * @dma_complete: DMA completion notifier
> */
> struct tegra_i2c_dev {
> struct device *dev;
> @@ -201,6 +225,7 @@ struct tegra_i2c_dev {
> struct clk *fast_clk;
> struct reset_control *rst;
> void __iomem *base;
> + phys_addr_t phys_addr;
> int cont_id;
> int irq;
> bool irq_disabled;
> @@ -214,8 +239,18 @@ struct tegra_i2c_dev {
> u16 clk_divisor_non_hs_mode;
> bool is_multimaster_mode;
> spinlock_t xfer_lock;
> + bool has_dma;
> + struct dma_chan *tx_dma_chan;
> + struct dma_chan *rx_dma_chan;
> + dma_addr_t dma_phys;
> + u32 *dma_buf;
> + unsigned int dma_buf_size;
> + bool is_curr_dma_xfer;
> + struct completion dma_complete;
> };
>
> +static struct dma_chan *chan;
> +
> static void dvc_writel(struct tegra_i2c_dev *i2c_dev, u32 val,
> unsigned long reg)
> {
> @@ -282,6 +317,75 @@ static void tegra_i2c_unmask_irq(struct tegra_i2c_dev *i2c_dev, u32 mask)
> i2c_writel(i2c_dev, int_mask, I2C_INT_MASK);
> }
>
> +static void tegra_i2c_dma_complete(void *args)
> +{
> + struct tegra_i2c_dev *i2c_dev = args;
> +
> + complete(&i2c_dev->dma_complete);
> +}
> +
> +static int tegra_i2c_dma_submit(struct tegra_i2c_dev *i2c_dev, size_t len)
> +{
> + struct dma_async_tx_descriptor *dma_desc;
> + enum dma_transfer_direction dir;
> +
> + dev_dbg(i2c_dev->dev, "Starting DMA for length: %zu\n", len);
> + reinit_completion(&i2c_dev->dma_complete);
> + dir = i2c_dev->msg_read ? DMA_DEV_TO_MEM : DMA_MEM_TO_DEV;
> + dma_desc = dmaengine_prep_slave_single(chan, i2c_dev->dma_phys,
> + len, dir, DMA_PREP_INTERRUPT |
> + DMA_CTRL_ACK);
> + if (!dma_desc) {
> + dev_err(i2c_dev->dev, "Failed to get DMA descriptor\n");
> + return -EIO;
> + }
> +
> + dma_desc->callback = tegra_i2c_dma_complete;
> + dma_desc->callback_param = i2c_dev;
> + dmaengine_submit(dma_desc);
> + dma_async_issue_pending(chan);
> + return 0;
> +}
> +
> +static int tegra_i2c_init_dma_param(struct tegra_i2c_dev *i2c_dev,
> + bool dma_to_memory)
> +{
> + struct dma_chan *dma_chan;
> + u32 *dma_buf;
> + dma_addr_t dma_phys;
> + int ret;
> + const char *chan_name = dma_to_memory ? "rx" : "tx";
> +
> + dma_chan = dma_request_slave_channel_reason(i2c_dev->dev, chan_name);
> + if (IS_ERR(dma_chan))
> + return PTR_ERR(dma_chan);
> +
> + dma_buf = dma_alloc_coherent(i2c_dev->dev, i2c_dev->dma_buf_size,
> + &dma_phys, GFP_KERNEL);
> +
> + if (!dma_buf) {
> + dev_err(i2c_dev->dev, "Failed to allocate the DMA buffer\n");
> + ret = -ENOMEM;
> + goto scrub;
> + }
> +
> + if (dma_to_memory)
> + i2c_dev->rx_dma_chan = dma_chan;
> + else
> + i2c_dev->tx_dma_chan = dma_chan;
> +
> + i2c_dev->dma_buf = dma_buf;
> + i2c_dev->dma_phys = dma_phys;
> +
> + return 0;
> +
> +scrub:
> + dma_free_coherent(i2c_dev->dev, i2c_dev->dma_buf_size,
> + dma_buf, dma_phys);
> + dma_release_channel(dma_chan);
> + return ret;
> +}
> +
> static int tegra_i2c_flush_fifos(struct tegra_i2c_dev *i2c_dev)
> {
> unsigned long timeout = jiffies + HZ;
> @@ -641,25 +745,45 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
> goto err;
> }
>
> - if (i2c_dev->msg_read && (status & I2C_INT_RX_FIFO_DATA_REQ)) {
> - if (i2c_dev->msg_buf_remaining)
> - tegra_i2c_empty_rx_fifo(i2c_dev);
> - else
> - BUG();
> - }
> + if (!i2c_dev->is_curr_dma_xfer) {
> + if (i2c_dev->msg_read && (status & I2C_INT_RX_FIFO_DATA_REQ)) {
> + if (i2c_dev->msg_buf_remaining)
> + tegra_i2c_empty_rx_fifo(i2c_dev);
> + else
> + BUG();
> + }
>
> - if (!i2c_dev->msg_read && (status & I2C_INT_TX_FIFO_DATA_REQ)) {
> - if (i2c_dev->msg_buf_remaining)
> - tegra_i2c_fill_tx_fifo(i2c_dev);
> - else
> - tegra_i2c_mask_irq(i2c_dev, I2C_INT_TX_FIFO_DATA_REQ);
> + if (!i2c_dev->msg_read &&
> + (status & I2C_INT_TX_FIFO_DATA_REQ)) {
> + if (i2c_dev->msg_buf_remaining)
> + tegra_i2c_fill_tx_fifo(i2c_dev);
> + else
> + tegra_i2c_mask_irq(i2c_dev,
> + I2C_INT_TX_FIFO_DATA_REQ);
> + }
> }
>
> i2c_writel(i2c_dev, status, I2C_INT_STATUS);
> if (i2c_dev->is_dvc)
> dvc_writel(i2c_dev, DVC_STATUS_I2C_DONE_INTR, DVC_STATUS);
>
> - if (status & I2C_INT_PACKET_XFER_COMPLETE) {
> + if (status & I2C_INT_ALL_PACKETS_XFER_COMPLETE) {
> + /*
> + * During message read XFER_COMPLETE interrupt is triggered prior to
> + * DMA complete notification and during message write XFER_COMPLETE
> + * interrupt is triggered after DMA complete notification.
> + * PACKETS_XFER_COMPLETE indicates completion of all bytes of transfer.
> + * so forcing msg_buf_remaining to 0.
> + */
> + if (i2c_dev->is_curr_dma_xfer)
> + i2c_dev->msg_buf_remaining = 0;
> + status |= I2C_INT_PACKET_XFER_COMPLETE;
> + i2c_writel(i2c_dev, status, I2C_INT_STATUS);
> + if (!i2c_dev->msg_buf_remaining)
> + complete(&i2c_dev->msg_complete);
> + } else if (status & I2C_INT_PACKET_XFER_COMPLETE) {
> + if (i2c_dev->is_curr_dma_xfer)
> + i2c_dev->msg_buf_remaining = 0;
> BUG_ON(i2c_dev->msg_buf_remaining);
> complete(&i2c_dev->msg_complete);
> }
> @@ -668,17 +792,68 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
> /* An error occurred, mask all interrupts */
> tegra_i2c_mask_irq(i2c_dev, I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST |
> I2C_INT_PACKET_XFER_COMPLETE | I2C_INT_TX_FIFO_DATA_REQ |
> - I2C_INT_RX_FIFO_DATA_REQ);
> + I2C_INT_RX_FIFO_DATA_REQ | I2C_INT_ALL_PACKETS_XFER_COMPLETE);
> i2c_writel(i2c_dev, status, I2C_INT_STATUS);
> if (i2c_dev->is_dvc)
> dvc_writel(i2c_dev, DVC_STATUS_I2C_DONE_INTR, DVC_STATUS);
>
> + if (i2c_dev->is_curr_dma_xfer) {
> + dmaengine_terminate_all(chan);
> + complete(&i2c_dev->dma_complete);
> + }
> +
> complete(&i2c_dev->msg_complete);
> done:
> spin_unlock(&i2c_dev->xfer_lock);
> return IRQ_HANDLED;
> }
>
> +static void tegra_i2c_config_fifo_trig(struct tegra_i2c_dev *i2c_dev,
> + size_t len, int direction)
> +{
> + u32 val, reg;
> + u8 dma_burst = 0;
> + struct dma_slave_config dma_sconfig;
> +
> + if (i2c_dev->hw->has_mst_fifo)
> + reg = I2C_MST_FIFO_CONTROL;
> + else
> + reg = I2C_FIFO_CONTROL;
> + val = i2c_readl(i2c_dev, reg);
> +
> + if (len & 0xF)
> + dma_burst = 1;
> + else if (len & 0x10)
> + dma_burst = 4;
> + else
> + dma_burst = 8;
> +
> + if (direction == DATA_DMA_DIR_TX) {
> + if (i2c_dev->hw->has_mst_fifo)
> + val |= I2C_MST_FIFO_CONTROL_TX_TRIG(dma_burst);
> + else
> + val |= I2C_FIFO_CONTROL_TX_TRIG(dma_burst);
> + } else {
> + if (i2c_dev->hw->has_mst_fifo)
> + val |= I2C_MST_FIFO_CONTROL_RX_TRIG(dma_burst);
> + else
> + val |= I2C_FIFO_CONTROL_RX_TRIG(dma_burst);
> + }
> + i2c_writel(i2c_dev, val, reg);
> +
> + if (direction == DATA_DMA_DIR_TX) {
> + dma_sconfig.dst_addr = i2c_dev->phys_addr + I2C_TX_FIFO;
> + dma_sconfig.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
> + dma_sconfig.dst_maxburst = dma_burst;
> + } else {
> + dma_sconfig.src_addr = i2c_dev->phys_addr + I2C_RX_FIFO;
> + dma_sconfig.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
> + dma_sconfig.src_maxburst = dma_burst;
> + }
> +
> + dmaengine_slave_config(chan, &dma_sconfig);
> +}
> +
> static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
> struct i2c_msg *msg, enum msg_end_type end_state)
> {
> @@ -688,6 +863,9 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
> unsigned long flags;
> u16 xfer_time = 100;
> size_t xfer_size = 0;
> + u32 *buffer = 0;
> + int ret = 0;
> + bool dma = false;
>
> if (msg->flags & I2C_M_RD)
> xfer_size = ALIGN(msg->len, BYTES_PER_FIFO_WORD);
> @@ -698,6 +876,11 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
> xfer_time += DIV_ROUND_CLOSEST((xfer_size * 9) * 1000,
> i2c_dev->bus_clk_rate);
>
> + dma = ((xfer_size > I2C_PIO_MODE_MAX_LEN) &&
> + i2c_dev->tx_dma_chan && i2c_dev->rx_dma_chan);

The xfer_size is aligned to 4, does this mean that DMA will transfer more bytes than needed when msg->len isn't multiple of 4?

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