Re: [PATCH v3 1/3] clk: qcom: gdsc: Fix the handling of PWRSTS_RET support

[Luca Weiss]

On Montag, 23. Jänner 2023 05:30:55 CET Rajendra Nayak wrote:
> On 1/22/2023 5:45 AM, Luca Weiss wrote:
> > Hi Rajendra,
> > 
> > On Dienstag, 20. September 2022 13:15:15 CET Rajendra Nayak wrote:
> >> GDSCs cannot be transitioned into a Retention state in SW.
> >> When either the RETAIN_MEM bit, or both the RETAIN_MEM and
> >> RETAIN_PERIPH bits are set, and the GDSC is left ON, the HW
> >> takes care of retaining the memory/logic for the domain when
> >> the parent domain transitions to power collapse/power off state.
> >> 
> >> On some platforms where the parent domains lowest power state
> >> itself is Retention, just leaving the GDSC in ON (without any
> >> RETAIN_MEM/RETAIN_PERIPH bits being set) will also transition
> >> it to Retention.
> >> 
> >> The existing logic handling the PWRSTS_RET seems to set the
> >> RETAIN_MEM/RETAIN_PERIPH bits if the cxcs offsets are specified
> >> but then explicitly turns the GDSC OFF as part of _gdsc_disable().
> >> Fix that by leaving the GDSC in ON state.
> >> 
> >> Signed-off-by: Rajendra Nayak <quic_rjendra@xxxxxxxxxxx>
> >> Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
> >> ---
> >> v3:
> >> Updated changelog
> >> 
> >> There are a few existing users of PWRSTS_RET and I am not
> >> sure if they would be impacted with this change
> >> 
> >> 1. mdss_gdsc in mmcc-msm8974.c, I am expecting that the
> >> gdsc is actually transitioning to OFF and might be left
> >> ON as part of this change, atleast till we hit system wide
> >> low power state.
> >> If we really leak more power because of this
> >> change, the right thing to do would be to update .pwrsts for
> >> mdss_gdsc to PWRSTS_OFF_ON instead of PWRSTS_RET_ON
> >> I dont have a msm8974 hardware, so if anyone who has can report
> >> any issues I can take a look further on how to fix it.
> > 
> > Unfortunately indeed this patch makes problems on msm8974, at least on
> > fairphone-fp2 hardware.
> > 
> > With this patch in place, the screen doesn't initialize correctly in maybe
> > 80% of boots and is stuck in weird states, mostly just becomes completely
> > blue.
> > 
> > Kernel log at least sometimes includes messages like this:
> > [   25.847541] dsi_cmds2buf_tx: cmd dma tx failed, type=0x39, data0=0x51,
> > len=8, ret=-110
> > 
> > Do you have anything I can try on msm8974? For now, reverting this patch
> > makes display work again on v6.1
> 
> hmm, I was really expecting this to leak more power than break anything
> functionally, Did you try moving to PWRSTS_OFF_ON instead of PWRSTS_RET_ON
> for mdss_gdsc?

Hi Rajendra,

yes with this change the display init works fine again. Do you think this is 
the intended solution then? I also haven't tested really more than this simple 
case.

Let me know what you think.

Regards
Luca

diff --git a/drivers/clk/qcom/mmcc-msm8974.c b/drivers/clk/qcom/mmcc-msm8974.c
index 26f3f8f06edf..f95e38abde13 100644
--- a/drivers/clk/qcom/mmcc-msm8974.c
+++ b/drivers/clk/qcom/mmcc-msm8974.c
@@ -2389,7 +2389,7 @@ static struct gdsc mdss_gdsc = {
 	.pd = {
 		.name = "mdss",
 	},
-	.pwrsts = PWRSTS_RET_ON,
+	.pwrsts = PWRSTS_OFF_ON,
 };
 
 static struct gdsc camss_jpeg_gdsc = {


> > Regards
> > Luca
> > 
> >> 2. gpu_gx_gdsc in gpucc-msm8998.c and
> >> 
> >>     gpu_gx_gdsc in gpucc-sdm660.c
> >> 
> >> Both of these seem to add support for 3 power state
> >> OFF, RET and ON, however I dont see any logic in gdsc
> >> driver to handle 3 different power states.
> >> So I am expecting that these are infact just transitioning
> >> between ON and OFF and RET state is never really used.
> >> The ideal fix for them would be to just update their resp.
> >> .pwrsts to PWRSTS_OFF_ON only.
> >> 
> >>   drivers/clk/qcom/gdsc.c | 10 ++++++++++
> >>   drivers/clk/qcom/gdsc.h |  5 +++++
> >>   2 files changed, 15 insertions(+)
> >> 
> >> diff --git a/drivers/clk/qcom/gdsc.c b/drivers/clk/qcom/gdsc.c
> >> index d3244006c661..ccf63771e852 100644
> >> --- a/drivers/clk/qcom/gdsc.c
> >> +++ b/drivers/clk/qcom/gdsc.c
> >> @@ -368,6 +368,16 @@ static int _gdsc_disable(struct gdsc *sc)
> >> 
> >>   	if (sc->pwrsts & PWRSTS_OFF)
> >>   	
> >>   		gdsc_clear_mem_on(sc);
> >> 
> >> +	/*
> >> +	 * If the GDSC supports only a Retention state, apart from ON,
> >> +	 * leave it in ON state.
> >> +	 * There is no SW control to transition the GDSC into
> >> +	 * Retention state. This happens in HW when the parent
> >> +	 * domain goes down to a Low power state
> >> +	 */
> >> +	if (sc->pwrsts == PWRSTS_RET_ON)
> >> +		return 0;
> >> +
> >> 
> >>   	ret = gdsc_toggle_logic(sc, GDSC_OFF);
> >>   	if (ret)
> >>   	
> >>   		return ret;
> >> 
> >> diff --git a/drivers/clk/qcom/gdsc.h b/drivers/clk/qcom/gdsc.h
> >> index 5de48c9439b2..981a12c8502d 100644
> >> --- a/drivers/clk/qcom/gdsc.h
> >> +++ b/drivers/clk/qcom/gdsc.h
> >> @@ -49,6 +49,11 @@ struct gdsc {
> >> 
> >>   	const u8			pwrsts;
> >>   
> >>   /* Powerdomain allowable state bitfields */
> >>   #define PWRSTS_OFF		BIT(0)
> >> 
> >> +/*
> >> + * There is no SW control to transition a GDSC into
> >> + * PWRSTS_RET. This happens in HW when the parent
> >> + * domain goes down to a low power state
> >> + */
> >> 
> >>   #define PWRSTS_RET		BIT(1)
> >>   #define PWRSTS_ON		BIT(2)
> >>   #define PWRSTS_OFF_ON		(PWRSTS_OFF | PWRSTS_ON)