Re: [PATCH 4/8] media: imx-pxp: explicitly disable unused blocks

Laurent Pinchart
2023-01-06T18:40:10Z

Hi Michael,

On Fri, Jan 06, 2023 at 03:08:55PM +0100, Michael Tretter wrote:
> On Fri, 06 Jan 2023 14:26:40 +0200, Laurent Pinchart wrote:
> > On Thu, Jan 05, 2023 at 02:47:25PM +0100, Michael Tretter wrote:
> > > Various multiplexers in the pipeline are not used with the currently
> > > configured data path. Disable all unused multiplexers by selecting the
> > > "no output" (3) option.
> > >
> > > The datasheet doesn't explicitly require this, but the PXP has been seen
> > > to hang after processing a few hundreds of frames otherwise.
> >
> > On which platform(s) have you noticed that ?
>
> I didn't observe this myself, but took this information from the comment in
> your earlier patch [0] that disables the unused multiplexers.
>
> https://lore.kernel.org/linux-media/20200510223100.11641-2-laurent.pinchart@ideasonboard.com/

I suppose I should trust myself :-)

> > > As at it, add documentation for the multiplexers that are actually
> > > relevant for the data path.
> > >
> > > Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
> > > ---
> > > drivers/media/platform/nxp/imx-pxp.c | 30 +++++++++++++++++-----------
> > > 1 file changed, 18 insertions(+), 12 deletions(-)
> > >
> > > diff --git a/drivers/media/platform/nxp/imx-pxp.c b/drivers/media/platform/nxp/imx-pxp.c
> > > index a957fee88829..6ffd07cda965 100644
> > > --- a/drivers/media/platform/nxp/imx-pxp.c
> > > +++ b/drivers/media/platform/nxp/imx-pxp.c
> > > @@ -731,22 +731,28 @@ static u32 pxp_data_path_ctrl0(struct pxp_ctx *ctx)
> > > u32 ctrl0;
> > >
> > > ctrl0 = 0;
> > > - ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX15_SEL(0);
> > > + ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX15_SEL(3);
> > > + /* Bypass Dithering x3CH */
> > > ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX14_SEL(1);
> > > - ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX13_SEL(0);
> > > + ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX13_SEL(3);
> > > + /* Select Rotation */
> > > ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX12_SEL(0);
> > > + /* Select LUT */
> > > ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX11_SEL(0);
> > > - ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX10_SEL(0);
> > > + ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX10_SEL(3);
> > > + /* Select MUX8 for LUT */
> > > ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX9_SEL(1);
> > > + /* Select CSC 2 */
> > > ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX8_SEL(0);
> > > - ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX7_SEL(0);
> > > - ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX6_SEL(0);
> > > - ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX5_SEL(0);
> > > - ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX4_SEL(0);
> > > + ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX7_SEL(3);
> > > + ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX6_SEL(3);
> > > + ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX5_SEL(3);
> > > + ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX4_SEL(3);
> > > + /* Bypass Rotation 2 */
> > > ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX3_SEL(0);
> > > - ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX2_SEL(0);
> > > - ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX1_SEL(0);
> > > - ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX0_SEL(0);
> > > + ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX2_SEL(3);
> > > + ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX1_SEL(3);
> > > + ctrl0 |= BF_PXP_DATA_PATH_CTRL0_MUX0_SEL(3);
> >
> > The muxes being disabled look fine to me, but the values of MUX8, MUX12
> > and MUX14 look strange based on the i.MX7D reference manual. Maybe the
> > register values were different in previous SoCs ? I haven't found any
> > other relevant reference manual that document the mux values, I may have
> > overlooked something.
>
> The MUX8, MUX12 and MUX14 are documented in the i.MX6ULL reference manual
> section 41.11.51 and their location and function in the data path is shown in
> Figure 41-1. "PXP Architecture" on page 2490.

I've seen that, but as far as I can tell, the description of the
register in section 41.11.51 doesn't tell what the different MUX* field
value map to. Figure 41-1 shows that, for instance, MUX8 handles CSC2
bypass, but it doesn't tell what value corresponds to what path.

> > Anyway, this isn't an issue with this patch, so
> >
> > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> >
> > >
> > > return ctrl0;
> > > }
> > > @@ -760,8 +766,8 @@ static void pxp_set_data_path(struct pxp_ctx *ctx)
> > > ctrl0 = pxp_data_path_ctrl0(ctx);
> > >
> > > ctrl1 = 0;
> > > - ctrl1 |= BF_PXP_DATA_PATH_CTRL1_MUX17_SEL(1);
> > > - ctrl1 |= BF_PXP_DATA_PATH_CTRL1_MUX16_SEL(1);
> > > + ctrl1 |= BF_PXP_DATA_PATH_CTRL1_MUX17_SEL(3);
> > > + ctrl1 |= BF_PXP_DATA_PATH_CTRL1_MUX16_SEL(3);
> > >
> > > writel(ctrl0, dev->mmio + HW_PXP_DATA_PATH_CTRL0);
> > > writel(ctrl1, dev->mmio + HW_PXP_DATA_PATH_CTRL1);

--
Regards,

Laurent Pinchart