Hi Kieran, On Thu, Sep 19, 2019 at 09:08:18AM +0100, Kieran Bingham wrote: > On 19/09/2019 00:23, Laurent Pinchart wrote: > > On Thu, Sep 12, 2019 at 10:19:30AM +0100, Kieran Bingham wrote: > >> On 12/09/2019 09:07, Jacopo Mondi wrote: > >>> On Wed, Sep 11, 2019 at 07:40:27PM +0100, Kieran Bingham wrote: > >>>> On 06/09/2019 14:54, Jacopo Mondi wrote: > >>>>> Enable/disable the CMM associated with a CRTC at CRTC start and stop > >>>>> time and enable the CMM unit through the Display Extensional Functions > >>>>> register at group setup time. > >>>>> > >>>>> Reviewed-by: Ulrich Hecht <uli+renesas@xxxxxxxx> > >>>>> Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> > >>>>> Signed-off-by: Jacopo Mondi <jacopo+renesas@xxxxxxxxxx> > >>>>> --- > >>>>> drivers/gpu/drm/rcar-du/rcar_du_crtc.c | 7 +++++++ > >>>>> drivers/gpu/drm/rcar-du/rcar_du_group.c | 8 ++++++++ > >>>>> drivers/gpu/drm/rcar-du/rcar_du_regs.h | 5 +++++ > >>>>> 3 files changed, 20 insertions(+) > >>>>> > >>>>> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c > >>>>> index 23f1d6cc1719..3dac605c3a67 100644 > >>>>> --- a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c > >>>>> +++ b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c > >>>>> @@ -21,6 +21,7 @@ > >>>>> #include <drm/drm_plane_helper.h> > >>>>> #include <drm/drm_vblank.h> > >>>>> > >>>>> +#include "rcar_cmm.h" > >>>>> #include "rcar_du_crtc.h" > >>>>> #include "rcar_du_drv.h" > >>>>> #include "rcar_du_encoder.h" > >>>>> @@ -619,6 +620,9 @@ static void rcar_du_crtc_stop(struct rcar_du_crtc *rcrtc) > >>>>> if (rcar_du_has(rcrtc->dev, RCAR_DU_FEATURE_VSP1_SOURCE)) > >>>>> rcar_du_vsp_disable(rcrtc); > >>>>> > >>>>> + if (rcrtc->cmm) > >>>>> + rcar_cmm_disable(rcrtc->cmm); > >>>>> + > >>>>> /* > >>>>> * Select switch sync mode. This stops display operation and configures > >>>>> * the HSYNC and VSYNC signals as inputs. > >>>>> @@ -686,6 +690,9 @@ static void rcar_du_crtc_atomic_enable(struct drm_crtc *crtc, > >>>>> } > >>>>> > >>>>> rcar_du_crtc_start(rcrtc); > >>>>> + > >>>>> + if (rcrtc->cmm) > >>>>> + rcar_cmm_enable(rcrtc->cmm); > >>>>> } > >>>>> > >>>>> static void rcar_du_crtc_atomic_disable(struct drm_crtc *crtc, > >>>>> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_group.c b/drivers/gpu/drm/rcar-du/rcar_du_group.c > >>>>> index 9eee47969e77..25d0fc125d7a 100644 > >>>>> --- a/drivers/gpu/drm/rcar-du/rcar_du_group.c > >>>>> +++ b/drivers/gpu/drm/rcar-du/rcar_du_group.c > >>>>> @@ -147,6 +147,14 @@ static void rcar_du_group_setup(struct rcar_du_group *rgrp) > >>>>> > >>>>> rcar_du_group_setup_pins(rgrp); > >>>>> > >>>>> + if (rcar_du_has(rcdu, RCAR_DU_FEATURE_CMM)) { > >>>>> + u32 defr7 = DEFR7_CODE > >>>>> + | (rgrp->cmms_mask & BIT(1) ? DEFR7_CMME1 : 0) > >>>>> + | (rgrp->cmms_mask & BIT(0) ? DEFR7_CMME0 : 0); > >>>>> + > >>>>> + rcar_du_group_write(rgrp, DEFR7, defr7); > >>>>> + } > >>>>> + > >>>> > >>>> What's the effect here on platforms with a CMM, but with > >>>> CONFIG_DRM_RCAR_CMM unset? > >>>> > >>>> Will this incorrectly configure the DU ? > >>>> > >>>> Will it stall the display if the DU tries to interact with another > >>>> module which is not enabled? > >>> > >>> I recall I tested that (that's why I had to add stubs for CMM > >>> functions, as I had linkage errors otherwise) and thing seems to be > >>> fine as the CMM configuration/enblement resolve to an empty function. > >> > >> Yes, I see the stubs to allow for linkage, but it's the hardware I'm > >> concerned about. If it passes the tests and doesn't break then that's > >> probably ok ... but I'm really weary that we're enabling a hardware > >> pipeline with a disabled component in the middle. > >> > >>> Would you prefer to have this guarded by an #if IS_ENABLED() ? > >> > >> I don't think we need a compile time conditional, but I'd say it > >> probably needs to be more about whether the CMM has actually probed or not > >> > >> Aha, and I see that in rcar_du_cmm_init() we already do a > >> call to rcar_cmm_init(), which if fails will leave rcdu->cmms[i] as > >> NULL. So that's catered for, which results in the rgrp->cmms_mask being > >> correctly representative of whether there is a CMM connected or not. > > > > Doesn't this result in probe failure ? > > I think I mis-spoke above, I didn't mean "if rcar_cmm_init() fails" I > meant "if rcar_du_cmm_init() determines there are no connected CMM's or > if they are disabled." > > If rcar_cmm_init() returns a failure, then yes we will fail to probe. > > But I think it's up to rcar_du_cmm_init() to determine if the CMM exists > or not (or is enabled) and if that's not a failure case then it should > not prevent the probing of the DU. > > In fact, I've now seen that if CONFIG_DRM_RCAR_CMM is not enabled, > rcar_cmm_init() returns 0, and I think in fact it should return -ENODEV, > with an exception on that return value in rcar_du_cmm_init() so that the > DU continues with no CMM attached there. I've replied to your other e-mail regarding this, and I agree with you. > >> ... so I think that means the ... > >> "if (rcar_du_has(rcdu, RCAR_DU_FEATURE_CMM))" is somewhat redundant: > >> > >> > >> This could be: > >> > >> if (rgrp->cmms_mask) { > >> u32 defr7 = DEFR7_CODE > >> | (rgrp->cmms_mask & BIT(1) ? DEFR7_CMME1 : 0) > >> | (rgrp->cmms_mask & BIT(0) ? DEFR7_CMME0 : 0); > >> > >> rcar_du_group_write(rgrp, DEFR7, defr7); > >> > >> Or in fact, if we don't mind writing 0 to DEFR7 when there is no CMM > >> (which is safe by the looks of things as DEFR7 is available on all > >> platforms), then we can even remove the outer conditional, and leave > >> this all up to the ternary operators to write the correct value to the > >> defr7. > >> > >> Phew ... net result - your current code *is* safe with the > >> CONFIG_DRM_RCAR_CMM option disabled. I'll leave it up to you if you want > >> to simplify the code here and remove the RCAR_DU_FEATURE_CMM. > >> > >> As this RCAR_DU_FEATURE_CMM flag is only checked here, removing it would > >> however simplify all of the rcar_du_device_info structures. > >> > >> So - with or without the _FEATURE_CMM" simplification, this patch looks > >> functional and safe so: > >> > >> > >> Reviewed-by: Kieran Bingham <kieran.bingham+renesas@xxxxxxxxxxxxxxxx> > >> > >>>>> if (rcdu->info->gen >= 2) { > >>>>> rcar_du_group_setup_defr8(rgrp); > >>>>> rcar_du_group_setup_didsr(rgrp); > >>>>> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_regs.h b/drivers/gpu/drm/rcar-du/rcar_du_regs.h > >>>>> index bc87f080b170..fb9964949368 100644 > >>>>> --- a/drivers/gpu/drm/rcar-du/rcar_du_regs.h > >>>>> +++ b/drivers/gpu/drm/rcar-du/rcar_du_regs.h > >>>>> @@ -197,6 +197,11 @@ > >>>>> #define DEFR6_MLOS1 (1 << 2) > >>>>> #define DEFR6_DEFAULT (DEFR6_CODE | DEFR6_TCNE1) > >>>>> > >>>>> +#define DEFR7 0x000ec > >>>>> +#define DEFR7_CODE (0x7779 << 16) > >>>>> +#define DEFR7_CMME1 BIT(6) > >>>>> +#define DEFR7_CMME0 BIT(4) > >>>>> + > >>>>> /* ----------------------------------------------------------------------------- > >>>>> * R8A7790-only Control Registers > >>>>> */ -- Regards, Laurent Pinchart