Re: [PATCH v2 3/3] i2c: qcom-geni: distinguish address-phase and data-phase NACK

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

On 7/9/2026 9:50 AM, Praveen Talari wrote:
> The M_GP_IRQ_1 interrupt signals a NACK condition, but does not
> distinguish whether it occurred during the address phase or the data
> phase.  The driver always attempted cancel and DMA FSM reset on any
> NACK, which is incorrect for an address NACK since the DMA engine was
> never armed and the hardware requires no recovery.
> 
> Add geni_i2c_check_addr_data_nack() to distinguish the two cases by
> reading SE_GENI_M_GP_LENGTH after the NACK event.  A zero value means
> the address phase was NACKed (ADDR_NACK) and no DMA recovery is needed.
> A non-zero value on a write transfer means a data byte was NACKed
> (DATA_NACK) and the normal cancel and DMA FSM reset path must run.
> 
> Co-developed-by: Naresh Maramaina <naresh.maramaina@oss.qualcomm.com>
> Signed-off-by: Naresh Maramaina <naresh.maramaina@oss.qualcomm.com>
> Signed-off-by: Praveen Talari <praveen.talari@oss.qualcomm.com>
> ---
>   drivers/i2c/busses/i2c-qcom-geni.c | 29 ++++++++++++++++++++---------
>   1 file changed, 20 insertions(+), 9 deletions(-)

[...]

>   #define I2C_AUTO_SUSPEND_DELAY	250
> @@ -143,7 +144,8 @@ struct geni_i2c_err_log {
>   
>   static const struct geni_i2c_err_log gi2c_log[] = {
>   	[GP_IRQ0] = {-EIO, "Unknown I2C err GP_IRQ0"},
> -	[NACK] = {-ENXIO, "NACK: slv unresponsive, check its power/reset-ln"},
> +	[ADDR_NACK] = {-ENXIO, "NACK: slv unresponsive, check its power/reset-ln"},
Now slv could be target device, follow latest convention.
> +	[DATA_NACK] = {-EIO, "Data NACK: device NACK before end of TX"},
Minor: Instead of before end of TX, could be simply TX transfer NACK ?
>   	[GP_IRQ2] = {-EIO, "Unknown I2C err GP IRQ2"},
>   	[BUS_PROTO] = {-EPROTO, "Bus proto err, noisy/unexpected start/stop"},
>   	[ARB_LOST] = {-EAGAIN, "Bus arbitration lost, clock line undriveable"},
> @@ -258,7 +260,8 @@ static void geni_i2c_err(struct geni_i2c_dev *gi2c, int err)
>   

[...]