Re: [PATCH v1 1/3] dmaengine: qcom: gpi: Add I2C bus recovery opcode support

[Mukesh Savaliya <mukesh.savaliya@oss.qualcomm.com>]

On 8/26/2026 3:21 PM, Aniket Randive wrote:
> The I2C_BUS_CLEAR and I2C_STOP_ON_BUS GENI sequencer opcodes release a
> stuck I2C bus, but the GPI DMA driver has no way to emit these
> zero-payload control commands, so an I2C controller using GPI DMA
> cannot recover the bus.
> 
> Add I2C_BUS_CLEAR and I2C_STOP_ON_BUS to enum i2c_op so I2C drivers can
> request them through gpi_i2c_config.op. Handle them in
> gpi_create_i2c_tre() by emitting a CONFIG TRE (when set_config is set)
> followed by a GO TRE with IEOT set and no DMA TRE, and reserve the
> matching number of ring entries in gpi_prep_slave_sg().
> 

start with problem statement which is being fixed by the respective patch.

Rest of the message can be simplified as below - more you can add.

Allow GPI DMA clients to issue the GENI I2C_BUS_CLEAR and
I2C_STOP_ON_BUS commands used for I2C bus recovery.

Add the new opcodes to the GPI I2C interface and generate the
corresponding CONFIG/GO TRE sequence without data DMA transfers.
Adjust TRE reservation logic to account for these commands.

> Signed-off-by: Aniket Randive <aniket.randive@oss.qualcomm.com>
> ---
>   drivers/dma/qcom/gpi.c           | 30 ++++++++++++++++++++++++++++++
>   include/linux/dma/qcom-gpi-dma.h |  2 ++
>   2 files changed, 32 insertions(+)
> 
> diff --git a/drivers/dma/qcom/gpi.c b/drivers/dma/qcom/gpi.c

[...]

> @@ -1825,6 +1843,18 @@ gpi_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
>   		nr_tre = 2;
>   	if (direction == DMA_DEV_TO_MEM) /* rx */
>   		nr_tre = 1;
> +	/*
> +	 * Recovery opcodes do not require DMA data TREs, only CONFIG
> +	 * (for set_config) and GO TREs. Since gpi_prep_slave_sg() is
> +	 * shared with SPI, verify the channel is I2C before accessing
Not only SPI, its for all GENI protocols. Can say common function for 
all protocols.

May be once such conditions are rising, we need to think of better way 
in design to handle such cases.
> +	 * the configuration data.
> +	 */
> +	if (gchan->protocol == QCOM_GPI_I2C) {
> +		struct gpi_i2c_config *i2c = gchan->config;
> +
> +		if (i2c->op == I2C_BUS_CLEAR || i2c->op == I2C_STOP_ON_BUS)
> +			nr_tre = set_config ? 2 : 1;
> +	}
>   

[...]