Re: [PATCH] media: iris: vpu3x: Add MNoC low power handshake during hardware power-off

[Jorge Ramirez <jorge.ramirez@oss.qualcomm.com>]

On 12/08/25 10:06:40, Neil Armstrong wrote:
> On 12/08/2025 09:48, Dikshita Agarwal wrote:
> > Add the missing write to AON_WRAPPER_MVP_NOC_LPI_CONTROL before
> > reading the LPI status register. Introduce a handshake loop to ensure
> > MNoC enters low power mode reliably during VPU3 hardware power-off with
> > timeout handling.
> > 
> > Signed-off-by: Dikshita Agarwal <quic_dikshita@quicinc.com>
> > ---
> >   drivers/media/platform/qcom/iris/iris_vpu3x.c | 23 +++++++++++++++++++++--
> >   1 file changed, 21 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/media/platform/qcom/iris/iris_vpu3x.c b/drivers/media/platform/qcom/iris/iris_vpu3x.c
> > index 9b7c9a1495ee2f51c60b1142b2ed4680ff798f0a..c2e6af575cbe4b3e3f2a019b24eecf3a5d469566 100644
> > --- a/drivers/media/platform/qcom/iris/iris_vpu3x.c
> > +++ b/drivers/media/platform/qcom/iris/iris_vpu3x.c
> > @@ -110,6 +110,7 @@ static void iris_vpu3_power_off_hardware(struct iris_core *core)
> >   static void iris_vpu33_power_off_hardware(struct iris_core *core)
> >   {
> >   	u32 reg_val = 0, value, i;
> > +	u32 count = 0;
> >   	int ret;
> >   	if (iris_vpu3x_hw_power_collapsed(core))
> > @@ -128,13 +129,31 @@ static void iris_vpu33_power_off_hardware(struct iris_core *core)
> >   			goto disable_power;
> >   	}
> > +	/* set MNoC to low power */
> > +	writel(REQ_POWER_DOWN_PREP, core->reg_base + AON_WRAPPER_MVP_NOC_LPI_CONTROL);
> > +
> > +	value = readl(core->reg_base + AON_WRAPPER_MVP_NOC_LPI_STATUS);
> > +

for readibility purposes, could this code be restructed a bit
differently? maybe all the write/read operations in a single do while
loop with the exit conditions assigned to variables with an
identifiable meaning?

maybe also check/report errors outside the loop itself?


> > +	while (!(value & BIT(0)) && (value & BIT(2) || value & BIT(1))) {
> > +		writel(0, core->reg_base + AON_WRAPPER_MVP_NOC_LPI_CONTROL);
> > +
> > +		usleep_range(10, 20);
> > +
> > +		writel(REQ_POWER_DOWN_PREP, core->reg_base + AON_WRAPPER_MVP_NOC_LPI_CONTROL);
> > +
> > +		value = readl(core->reg_base + AON_WRAPPER_MVP_NOC_LPI_STATUS);
> > +		if (++count >= 1000) {
> > +			dev_err(core->dev, "LPI handshake timeout\n");
> > +			break;
> > +		}
> > +	}
> > +
> >   	ret = readl_poll_timeout(core->reg_base + AON_WRAPPER_MVP_NOC_LPI_STATUS,
> >   				 reg_val, reg_val & BIT(0), 200, 2000);
> >   	if (ret)
> >   		goto disable_power;
> > -	/* set MNoC to low power, set PD_NOC_QREQ (bit 0) */
> > -	writel(BIT(0), core->reg_base + AON_WRAPPER_MVP_NOC_LPI_CONTROL);
> > +	writel(0, core->reg_base + AON_WRAPPER_MVP_NOC_LPI_CONTROL);
> >   	writel(CORE_BRIDGE_SW_RESET | CORE_BRIDGE_HW_RESET_DISABLE,
> >   	       core->reg_base + CPU_CS_AHB_BRIDGE_SYNC_RESET);
> > 
> > ---
> > base-commit: d968e50b5c26642754492dea23cbd3592bde62d8
> > change-id: 20250812-sm8650-power-sequence-fix-ba9a92098233
> > 
> > Best regards,
> 
> Tested-by: Neil Armstrong <neil.armstrong@linaro.org> # on SM8650-HDK
> 
> Thanks,
> Neil
>