Re: [PATCH 1/2] dmaengine: qcom-gpi: Add I2C High-Speed mode configuration support

From: Mukesh Savaliya

Date: Thu Aug 27 2026 - 15:28:21 EST



On 8/24/2026 4:55 PM, Jyothi Kumar Seerapu wrote:
Add support in the Qualcomm GPI (Generic Packet Interface) DMA engine
to configure I2C High-Speed (HS) mode transfers.

Introduce support for CONFIG1 Transfer Ring Element (TRE) to convey
HS-specific timing parameters to the hardware. Define a new
gpi_i2c_config1 structure containing tcycle_cnt and tlow_cnt fields,
with default values of 28 and 38 respectively, as required for 3.4 MHz
HS mode operation.

Little more enhanced -

dmaengine: qcom: gpi: Add I2C High-Speed mode frequency support

Introduce CONFIG1 Transfer Ring Element (TRE) support to program
I2C High-Speed (HS) mode timing parameters through the Qualcomm
GPI DMA engine.

Add a new gpi_i2c_config1 structure containing tcycle_cnt and
tlow_cnt fields. The fields are initialized to the hardware
recommended values of 28 and 38, enabling 3.4 MHz HS-mode I2C
transfers.


Signed-off-by: Jyothi Kumar Seerapu <jyothi.seerapu@xxxxxxxxxxxxxxxx>
---
drivers/dma/qcom/gpi.c | 54 +++++++++++++++++++++++++++++++++++-----
include/linux/dma/qcom-gpi-dma.h | 28 ++++++++++++++++++++-
2 files changed, 75 insertions(+), 7 deletions(-)

diff --git a/drivers/dma/qcom/gpi.c b/drivers/dma/qcom/gpi.c
index a5055a6273af..52a7800ed4f5 100644
--- a/drivers/dma/qcom/gpi.c
+++ b/drivers/dma/qcom/gpi.c
@@ -21,6 +21,7 @@
#define TRE_TYPE_IMMEDIATE_DMA 0x11
#define TRE_TYPE_GO 0x20
#define TRE_TYPE_CONFIG0 0x22
+#define TRE_TYPE_CONFIG1 0x23
/* TRE flags */
#define TRE_FLAGS_CHAIN BIT(0)
@@ -58,9 +59,14 @@
#define TRE_I2C_C0_TX_PACK BIT(24)
#define TRE_I2C_C0_RX_PACK BIT(25)
+/* I2C Config1 WD0 */
+#define TRE_I2C_C1_TLOW GENMASK(9, 0)
+#define TRE_I2C_C1_TCYCLE GENMASK(19, 10)
+

Not sure why above two not looking aligned by tab

/* I2C GO WD0 */
#define TRE_I2C_GO_CMD GENMASK(4, 0)

[...]

- /* create the GO tre for Tx */
- if (i2c->op == I2C_WRITE) {
+ /* Create CONFIG1 TRE if requested */
+ if (i2c->set_config1) {
can we move this set_config1 into else if part of set_config, above ?> tre = &desc->tre[tre_idx];
tre_idx++;
+ /* CONFIG1 TRE with timing parameters */
+ tre->dword[0] = u32_encode_bits(i2c->config1.tlow_cnt, TRE_I2C_C1_TLOW);
+ tre->dword[0] |= u32_encode_bits(i2c->config1.tcycle_cnt, TRE_I2C_C1_TCYCLE);
+ tre->dword[1] = 0;
+ tre->dword[2] = 0;
+ tre->dword[3] = u32_encode_bits(TRE_TYPE_CONFIG1, TRE_FLAGS_TYPE);
+ tre->dword[3] |= u32_encode_bits(1, TRE_FLAGS_CHAIN);
+ }
+
+ /* create the GO tre for Tx */
+ if (i2c->op == I2C_WRITE || i2c->op == I2C_HS_WRITE) {
+ u8 master_code = 0; /* Default master code for Linux EE */
why for Linux EE ? what else could be ?> + u32 cmd_opcode;
+ bool is_hs_mode = false;
+
+ tre = &desc->tre[tre_idx];
+ tre_idx++;
+
+ is_hs_mode = (i2c->op == I2C_HS_WRITE || i2c->op == I2C_HS_READ);
+
+ /* Determine the command opcode based on HS mode and multi_msg flag */
Comment is mostly restates the code, would write as -
/* Select HS-mode or standard I2C opcode. */
if (i2c->multi_msg)
- tre->dword[0] = u32_encode_bits(I2C_READ, TRE_I2C_GO_CMD);
+ cmd_opcode = is_hs_mode ? I2C_HS_READ : I2C_READ;
can you add explanation of cmd opcode into commit log too ? That would make story describing changes.> else
- tre->dword[0] = u32_encode_bits(i2c->op, TRE_I2C_GO_CMD);
+ /* I2C HS write vs Regular I2C write */
+ cmd_opcode = is_hs_mode ? I2C_HS_WRITE : i2c->op;
+
what if i write as below, will be simplified ?
i2c->op = cmd_opcode ; //OR can store directly into i2c->op.
tre->dword[0] = u32_encode_bits(i2c->op, TRE_I2C_GO_CMD);

+ tre->dword[0] = u32_encode_bits(cmd_opcode, TRE_I2C_GO_CMD);
+
+ if (is_hs_mode)
+ tre->dword[0] |= u32_encode_bits(master_code, TRE_I2C_GO_MASTER_CODE);
tre->dword[0] |= u32_encode_bits(i2c->addr, TRE_I2C_GO_ADDR);
tre->dword[0] |= u32_encode_bits(i2c->stretch, TRE_I2C_GO_STRETCH);
@@ -1674,7 +1708,7 @@ static int gpi_create_i2c_tre(struct gchan *chan, struct gpi_desc *desc,
tre->dword[3] |= u32_encode_bits(1, TRE_FLAGS_CHAIN);
}
- if (i2c->op == I2C_READ || i2c->multi_msg == false) {
+ if (i2c->op == I2C_READ || i2c->op == I2C_HS_READ || i2c->multi_msg == false) {
/* create the DMA TRE */
tre = &desc->tre[tre_idx];
tre_idx++;
@@ -1826,6 +1860,14 @@ gpi_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
if (direction == DMA_DEV_TO_MEM) /* rx */
nr_tre = 1;
+ /* I2C High-Speed mode sends an extra CONFIG1 TRE ahead of the GO TRE */
+ if (gchan->protocol == QCOM_GPI_I2C) {
+ struct gpi_i2c_config *i2c = gchan->config;
+
+ if (i2c->set_config1)
+ nr_tre++;
+ }
+
/* calculate # of elements required & available */
nr = gpi_ring_num_elements_avail(ch_ring);
if (nr < nr_tre) {
diff --git a/include/linux/dma/qcom-gpi-dma.h b/include/linux/dma/qcom-gpi-dma.h
index 332be28427e4..6e9f09fc109a 100644
--- a/include/linux/dma/qcom-gpi-dma.h
+++ b/include/linux/dma/qcom-gpi-dma.h

[...]

/**
@@ -62,15 +82,19 @@ enum i2c_op {
* @high_count: high period of clock
* @low_count: low period of clock
* @clk_div: source clock divider
+ * @clk_src: serial clock
source clock right ?> * @addr: i2c bus address
* @stretch: stretch the clock at eot
- * @set_config: set peripheral config
+ * @set_config: set peripheral config (CONFIG0)
+ * @set_config1: set peripheral config1 (CONFIG1)
+ * @config1: I2C HS mode timing configuration (CONFIG1 TRE parameters)
* @rx_len: receive length for buffer
* @op: i2c cmd
* @multi_msg: is part of multi i2c r-w msgs
*/
struct gpi_i2c_config {
u8 set_config;
+ u8 set_config1;
u8 pack_enable;
u8 cycle_count;
u8 high_count;
@@ -78,6 +102,8 @@ struct gpi_i2c_config {
u8 addr;
u8 stretch;
u16 clk_div;
+ u32 clk_src;
+ struct gpi_i2c_config1 config1;
u32 rx_len;
enum i2c_op op;
bool multi_msg;