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SubjectRe: [PATCH V12 3/5] i2c: tegra: Add DMA support
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06.02.2019 1:46, 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. This adds delay between data bytes of the same
> transfer when CPU is fully loaded and some slave devices has
> internal timeout for no bus activity and stops transaction to
> avoid bus hang. DMA mode is helpful in such cases.
>
> DMA mode is also helpful for Large transfers during downloading or
> uploading FW over I2C to some external devices.
>
> Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
> ---
> [V12] : Replaced dma_alloc_coherent with dma_alloc_attrs to force the allocated
> buffer to be contiguous also in physical memory as Tegra194 supports max
> 64K and dma_alloc_coherent doesnt guarentee contiguous memory.
> Changed return code from EIO to EINVAL incase of failure to obtain dma
> descriptor.
> Fixed coding style check issues.
> [V11] : Replaced deprecated dmaengine_terminate_all with dmaengine_termine_async
> from non-atomic context and dmaengine_terminate_sync from atomic context.
> Fixed to program fifo trigger levels properly when transfer falls back to
> pio mode in case of dma slave configuration failure and other minor fixes.
> [V10] : APBDMA is replaced with GPCDMA on Tegra186 and Tegra194 designs.
> Added apbdma hw support flag to now allow Tegra186 and later use
> APBDMA driver.
> Added explicit flow control enable for DMA slave config and error handling.
> Moved releasing DMA resources to seperate function to reuse in
> multiple places.
> Updated to register tegra_i2c_driver from module level rather than subsys
> level.
> Other minor feedback
> [V9] : Rebased to 5.0-rc4
> Removed dependency of APB DMA in Kconfig and added conditional check
> in I2C driver to decide on using DMA mode.
> Changed back the allocation of dma buffer during i2c probe.
> Fixed FIFO triggers depending on DMA Vs PIO.
> [V8] : Moved back dma init to i2c probe, removed ALL_PACKETS_XFER_COMPLETE
> interrupt and using PACKETS_XFER_COMPLETE interrupt only and some
> other fixes
> Updated Kconfig for APB_DMA dependency
> [V7] : Same as V6
> [V6] : Updated for proper buffer allocation/freeing, channel release.
> Updated to use exact xfer size for syncing dma buffer.
> [V5] : Same as V4
> [V4] : Updated to allocate DMA buffer only when DMA mode.
> Updated to fall back to PIO mode when DMA channel request or
> buffer allocation fails.
> [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 | 413 ++++++++++++++++++++++++++++++++++++-----
> 1 file changed, 369 insertions(+), 44 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index 118b7023a0f4..77277a09e485 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>

We are not using DMA pools anywhere in the code, <linux/dmapool.h> isn't needed. Let's remove it.

> +#include <linux/dma-mapping.h>
> #include <linux/err.h>
> #include <linux/i2c.h>
> #include <linux/init.h>
> @@ -44,6 +47,8 @@
> #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
> @@ -125,6 +130,19 @@
> #define I2C_MST_FIFO_STATUS_TX_MASK 0xff0000
> #define I2C_MST_FIFO_STATUS_TX_SHIFT 16
>
> +/* Packet header size in bytes */
> +#define I2C_PACKET_HEADER_SIZE 12
> +
> +#define DATA_DMA_DIR_TX BIT(0)
> +#define DATA_DMA_DIR_RX BIT(1)

The DATA_DMA_DIR_TX/RX are not used anywhere in the code, let's remove them.

[snip]

TEGRA_I2C_TIMEOUT);
> tegra_i2c_mask_irq(i2c_dev, int_mask);
> @@ -814,6 +1133,7 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
> time_left, completion_done(&i2c_dev->msg_complete),
> i2c_dev->msg_err);
>
> + i2c_dev->is_curr_dma_xfer = false;

This line could be removed because there is no need to clear "is_curr_dma_xfer" at this point.

> if (likely(i2c_dev->msg_err == I2C_ERR_NONE))
> return 0;
[snip]


Sowjanya, I tried to enforce DMA transferring + setting DMA burst to a one word and this combination doesn't work well while it should, if I'm not missing something. Could you please take a look at the problem or explain why that happens?

Here is the change I made:

-----------------
diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index c538ed5f8e2c..59e245d4417d 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -6,6 +6,8 @@
* Author: Colin Cross <ccross@android.com>
*/

+#define DEBUG
+
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/dmaengine.h>
@@ -929,12 +931,7 @@ static void tegra_i2c_config_fifo_trig(struct tegra_i2c_dev *i2c_dev,
val = i2c_readl(i2c_dev, reg);

if (i2c_dev->is_curr_dma_xfer) {
- if (len & 0xF)
dma_burst = 1;
- else if (len & 0x10)
- dma_burst = 4;
- else
- dma_burst = 8;

if (i2c_dev->msg_read) {
chan = i2c_dev->rx_dma_chan;
@@ -1046,8 +1043,7 @@ 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->dma_buf;
+ i2c_dev->is_curr_dma_xfer = !!i2c_dev->dma_buf;
tegra_i2c_config_fifo_trig(i2c_dev, xfer_size);
dma = i2c_dev->is_curr_dma_xfer
-----------------
And here what happens:

-----------------
...
[ 0.761144] tegra_rtc 7000e000.rtc: registered as rtc1
[ 0.761199] tegra_rtc 7000e000.rtc: Tegra internal Real Time Clock
[ 0.761406] i2c /dev entries driver
[ 0.919233] tegra-i2c 7000c000.i2c: starting DMA for length: 16
[ 0.919246] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 0.919345] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 0.919355] tegra-i2c 7000c000.i2c: starting DMA for length: 8
[ 0.919363] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 0.919628] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 0.919641] tegra-i2c 7000c000.i2c: starting DMA for length: 16
[ 0.919649] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 0.919746] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 0.919755] tegra-i2c 7000c000.i2c: starting DMA for length: 112
[ 0.919763] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 0.923140] tegra-i2c 7000c000.i2c: transfer complete: 11 0 0
[ 0.923150] atmel_mxt_ts 0-004c: Family: 160 Variant: 0 Firmware V1.0.AA Objects: 18
[ 0.923208] tegra-i2c 7000c000.i2c: starting DMA for length: 16
[ 0.923217] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 0.923314] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 0.923323] tegra-i2c 7000c000.i2c: starting DMA for length: 224
[ 0.923331] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 0.933564] tegra-i2c 7000c000.i2c: transfer complete: 11 0 0
[ 0.933599] tegra-i2c 7000c000.i2c: starting DMA for length: 16
[ 0.933609] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 0.933760] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 0.933770] tegra-i2c 7000c000.i2c: starting DMA for length: 12
[ 0.933779] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 0.934284] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 0.934309] tegra-i2c 7000c000.i2c: starting DMA for length: 16
[ 0.934317] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 0.934500] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 0.934509] tegra-i2c 7000c000.i2c: starting DMA for length: 12
[ 0.934518] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 0.935023] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 0.935081] tegra-i2c 7000c000.i2c: starting DMA for length: 16
[ 0.935091] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 0.935240] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 0.935249] tegra-i2c 7000c000.i2c: starting DMA for length: 4
[ 0.935258] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 0.935399] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 0.935416] tegra-i2c 7000c000.i2c: starting DMA for length: 16
[ 0.935424] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 0.935655] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 0.945445] tegra-i2c 7000d000.i2c: starting DMA for length: 16
[ 0.945456] tegra-i2c 7000d000.i2c: unmasked irq: 0c
[ 0.969236] tegra-i2c 7000c000.i2c: starting DMA for length: 16
[ 0.969245] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 0.969361] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 0.969370] tegra-i2c 7000c000.i2c: starting DMA for length: 4
[ 0.969379] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 0.969462] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 0.982587] tegra-i2c 7000c000.i2c: starting DMA for length: 16
[ 0.982596] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 0.982722] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 0.982731] tegra-i2c 7000c000.i2c: starting DMA for length: 12
[ 0.982740] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 0.983071] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 0.983090] tegra-i2c 7000c000.i2c: starting DMA for length: 16
[ 0.983098] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 0.983252] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 0.983261] tegra-i2c 7000c000.i2c: starting DMA for length: 136
[ 0.983269] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 0.987605] tegra-i2c 7000c000.i2c: transfer complete: 11 0 0
[ 0.987623] tegra-i2c 7000c000.i2c: starting DMA for length: 16
[ 0.987631] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 0.987800] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 0.987809] tegra-i2c 7000c000.i2c: starting DMA for length: 12
[ 0.987817] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 0.988324] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 1.009227] tegra-i2c 7000c000.i2c: starting DMA for length: 16
[ 1.009236] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 1.009374] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 1.009383] tegra-i2c 7000c000.i2c: starting DMA for length: 4
[ 1.009391] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 1.009479] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 1.009497] atmel_mxt_ts 0-004c: Warning: Info CRC error - device=0xF436DC file=0x000000
[ 1.009588] tegra-i2c 7000c000.i2c: starting DMA for length: 272
[ 1.009597] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 1.017483] tegra-i2c 7000c000.i2c: transfer complete: 11 0 0
[ 1.017496] tegra-i2c 7000c000.i2c: starting DMA for length: 120
[ 1.017504] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 1.020896] tegra-i2c 7000c000.i2c: transfer complete: 11 0 0
[ 1.020909] tegra-i2c 7000c000.i2c: starting DMA for length: 16
[ 1.020918] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 1.021055] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 1.032230] tegra-i2c 7000c000.i2c: starting DMA for length: 16
[ 1.032239] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 1.032359] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 1.032368] tegra-i2c 7000c000.i2c: starting DMA for length: 12
[ 1.032376] tegra-i2c 7000c000.i2c: unmasked irq: 0c
[ 1.032704] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0
[ 1.049224] tegra-i2c 7000d000.i2c: i2c transfer timed out
[ 1.049253] tps6586x 3-0034: Chip ID read failed: -110
[ 1.049281] tps6586x: probe of 3-0034 failed with error -5
...
-----------------
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