Re: [PATCH 15/28] media: ti-vpe: cal: remove wait when stopping camerarx

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Tomi,

On Mon, Apr 19, 2021 at 02:29:20PM +0300, Tomi Valkeinen wrote:
> On 18/04/2021 15:46, Laurent Pinchart wrote:
> > On Mon, Apr 12, 2021 at 02:34:44PM +0300, Tomi Valkeinen wrote:
> >> Asserting ComplexIO reset seems to affect the HW (ie. asserting reset
> >> will break an active capture), but the RESET_DONE bit never changes to
> >> "reset is ongoing" state. Thus we always get a timeout.
> >>
> >> Drop the wait, as it seems to achieve nothing.
> >>
> >> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
> >> ---
> >>   drivers/media/platform/ti-vpe/cal-camerarx.c | 15 ++-------------
> >>   1 file changed, 2 insertions(+), 13 deletions(-)
> >>
> >> diff --git a/drivers/media/platform/ti-vpe/cal-camerarx.c b/drivers/media/platform/ti-vpe/cal-camerarx.c
> >> index 0354f311c5d2..245c601b992c 100644
> >> --- a/drivers/media/platform/ti-vpe/cal-camerarx.c
> >> +++ b/drivers/media/platform/ti-vpe/cal-camerarx.c
> >> @@ -405,7 +405,6 @@ static int cal_camerarx_start(struct cal_camerarx *phy)
> >>   
> >>   static void cal_camerarx_stop(struct cal_camerarx *phy)
> >>   {
> >> -	unsigned int i;
> >>   	int ret;
> >>   
> >>   	cal_camerarx_ppi_disable(phy);
> >> @@ -419,19 +418,9 @@ static void cal_camerarx_stop(struct cal_camerarx *phy)
> >>   			CAL_CSI2_COMPLEXIO_CFG_RESET_CTRL,
> >>   			CAL_CSI2_COMPLEXIO_CFG_RESET_CTRL_MASK);
> >>   
> >> -	/* Wait for power down completion */
> >> -	for (i = 0; i < 10; i++) {
> >> -		if (cal_read_field(phy->cal,
> >> -				   CAL_CSI2_COMPLEXIO_CFG(phy->instance),
> >> -				   CAL_CSI2_COMPLEXIO_CFG_RESET_DONE_MASK) ==
> >> -		    CAL_CSI2_COMPLEXIO_CFG_RESET_DONE_RESETONGOING)
> > 
> > Isn't this the wrong condition ? I would have expected
> > CAL_CSI2_COMPLEXIO_CFG_RESET_DONE_RESETCOMPLETED, not
> > CAL_CSI2_COMPLEXIO_CFG_RESET_DONE_RESETONGOING. That could explain why
> > you always get a timeout.
> 
> No, I don't think so. The complexio reset is set active just before the 
> wait. So the reset status should show reset ongoing, until at some point 
> we release the reset (we do that when starting the PHY again).
>
> The TRM doesn't talk about this, though. So, I guess the status might go 
> to RESETONGOING for a very short time and back to RESETCOMPLETED before 
> the code can see the RESETONGOING. But I suspect the status just stays 
> at RESETCOMPLETED.

The TRM is indeed not very clear. My understanding was that asserting
RESET_CTRL initiates the reset, and RESET_DONE switches to 1 once the
reset completes. There's however a note in the initialization sequence
that states

a. Deassert the CAMERARX reset:
i. Set CAL_CSI2_COMPLEXIO_CFG_j[30] RESET_CTRL to 0x1.
CAUTION
For the CAL_CSI2_COMPLEXIO_CFG_j[29] RESET_DONE bit to be set to 0x1
(reset completed), the external sensor must to be active and sending the
MIPI HS BYTECLK (that is, RXBYTECLKHS clock).

The RESET_DONE bit may thus only toggle when de-asserting the reset
signal (by setting RESET_CTRL to 1). It would be useful to test that
hypothesis by reading RESET_DONE just before setting RESET_CTRL to 1,
and right after. I'd expect the values to be 0 and 1 respectively. If
that's the case, then this patch is likely correct, so

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>


The register macros are quite confusing by the way. We have

#define CAL_CSI2_COMPLEXIO_CFG_RESET_CTRL_MASK          BIT(30)
#define CAL_CSI2_COMPLEXIO_CFG_RESET_CTRL                       0
#define CAL_CSI2_COMPLEXIO_CFG_RESET_CTRL_OPERATIONAL           1

When reading the code, I thought

        cal_write_field(phy->cal, CAL_CSI2_COMPLEXIO_CFG(phy->instance),
                        CAL_CSI2_COMPLEXIO_CFG_RESET_CTRL,
                        CAL_CSI2_COMPLEXIO_CFG_RESET_CTRL_MASK)

meant that we were setting the reset bit to 1. I would personally get
rid of the _MASK suffixes for single bits, and use 0 and 1 in the code
instead of CAL_CSI2_COMPLEXIO_CFG_RESET_CTRL and
CAL_CSI2_COMPLEXIO_CFG_RESET_CTRL_OPERATIONAL.

-- 
Regards,

Laurent Pinchart