[PATCH] drm: xlnx: call pm_runtime_get_sync before setting pixel clock
Rohit Visavalia
RVISAVAL at xilinx.com
Wed Mar 17 11:17:16 GMT 2021
Hi Quanyang & Laurent,
I tested this patch(which moves pm_runtime_get_sync at the very beginning of the function zynqmp_disp_crtc_atomic_enable), i don't see any behavior change with patch, means with patch also DP display is not getting up and it is required to resolution change to make it up.
Also valid bit is not getting set for VPLL_FRAC_CFG on bootup, same behavior as without patch.
Thanks,
Rohit
> -----Original Message-----
> From: Michal Simek <michal.simek at xilinx.com>
> Sent: Wednesday, March 17, 2021 1:56 PM
> To: quanyang.wang <quanyang.wang at windriver.com>; Laurent Pinchart
> <laurent.pinchart at ideasonboard.com>; Rohit Visavalia
> <RVISAVAL at xilinx.com>
> Cc: Hyun Kwon <hyunk at xlnx.xilinx.com>; David Airlie <airlied at linux.ie>;
> Daniel Vetter <daniel at ffwll.ch>; Michal Simek <michals at xilinx.com>; dri-
> devel at lists.freedesktop.org; linux-arm-kernel at lists.infradead.org; linux-
> kernel at vger.kernel.org
> Subject: Re: [PATCH] drm: xlnx: call pm_runtime_get_sync before setting pixel
> clock
>
> +Rohit
>
> On 3/17/21 4:00 AM, quanyang.wang wrote:
> > Hi Laurent,
> >
> > On 3/17/21 4:32 AM, Laurent Pinchart wrote:
> >> Hi Quanyang,
> >>
> >> Thank you for the patch.
> >>
> >> On Wed, Mar 10, 2021 at 12:59:45PM +0800,
> quanyang.wang at windriver.com
> >> wrote:
> >>> From: Quanyang Wang <quanyang.wang at windriver.com>
> >>>
> >>> The Runtime PM subsystem will force the device "fd4a0000.zynqmp-
> display"
> >>> to enter suspend state while booting if the following conditions are
> >>> met:
> >>> - the usage counter is zero (pm_runtime_get_sync hasn't been called
> >>> yet)
> >>> - no 'active' children (no zynqmp-dp-snd-xx node under dpsub node)
> >>> - no other device in the same power domain (dpdma node has no
> >>> "power-domains = <&zynqmp_firmware PD_DP>" property)
> >>>
> >>> So there is a scenario as below:
> >>> 1) DP device enters suspend state <- call zynqmp_gpd_power_off
> >>> 2) zynqmp_disp_crtc_setup_clock <- configurate register
> >>> VPLL_FRAC_CFG
> >>> 3) pm_runtime_get_sync <- call zynqmp_gpd_power_on and
> >>> clear previous
> >>> VPLL_FRAC_CFG configuration
> >>> 4) clk_prepare_enable(disp->pclk) <- enable failed since
> >>> VPLL_FRAC_CFG
> >>> configuration is corrupted
> >>>
> >>> From above, we can see that pm_runtime_get_sync may clear register
> >>> VPLL_FRAC_CFG configuration and result the failure of clk enabling.
> >>> Putting pm_runtime_get_sync at the very beginning of the function
> >>> zynqmp_disp_crtc_atomic_enable can resolve this issue.
> >> Isn't this an issue in the firmware though, which shouldn't clear the
> >> previous VPLLF_FRAC_CFG ?
> >
> > Thank you for your review. I used to look into the atf and PWU code
> > and it seems (I didn't add debug code
> >
> > to PMU to make sure if PMU really does this, I only in kernel call
> > zynqmp_pm_get_pll_frac_data to make sure that
> >
> > the value in data field of VPLL_FRAC_CFG register is changed from
> > 0x4000 to 0x0 after run pm_runtime_get_sync)
> >
> > that PMU intends to reset VPLL when there is an Off and On in DP
> > Powerdomain.
> >
> >
> > Linux ATF PWU
> >
> > zynqmp_gpd_power_on
> > ->zynqmp_pm_set_requirement
> > -->send PM_SET_REQUIREMENT to ATF ==> ATF send ipi to PWU
> > ==> PmSetRequirement
> > ->PmRequirementUpdate
> > -->PmUpdateSlave(masterReq->slave)
> > --->PmSlaveChangeState
> > ---->PmSlaveChangeState
> > ----->PmSlaveClearAfterState
> > ------>PmClockRelease
> >
> > ------->PmClockReleaseInt(&ch->clock->base)
> > -------->clk->class->release(clk)
> > --------->PmPllBypassAndReset
> > //Here reset the VPLL then VPLL_FRAC_CFG is cleared.
> >
> >>
> >>> Signed-off-by: Quanyang Wang <quanyang.wang at windriver.com>
> >> Nonetheless, this change looks good to me, I actually had the same
> >> patch in my tree while investigation issues related to the clock
> >> rate, so
> >>
> >> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> >> Tested-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> >>
> >> I was hoping it would solve the issue I'm experiencing with the DP
> >> clock, but that's not the case :-( In a nutshell, when the DP is
> >> first started, the clock frequency is incorrect. The following quick
> >> & dirty patch fixes the problem:
> >>
> >> diff --git a/drivers/gpu/drm/xlnx/zynqmp_disp.c
> >> b/drivers/gpu/drm/xlnx/zynqmp_disp.c
> >> index 74ac0a064eb5..fdbe1b0640aa 100644
> >> --- a/drivers/gpu/drm/xlnx/zynqmp_disp.c
> >> +++ b/drivers/gpu/drm/xlnx/zynqmp_disp.c
> >> @@ -1439,6 +1439,10 @@ zynqmp_disp_crtc_atomic_enable(struct
> drm_crtc
> >> *crtc,
> >>
> >> pm_runtime_get_sync(disp->dev);
> >>
> >> + ret = clk_prepare_enable(disp->pclk);
> >> + if (!ret)
> >> + clk_disable_unprepare(disp->pclk);
> >> +
> >> zynqmp_disp_crtc_setup_clock(crtc, adjusted_mode);
> >>
> >> ret = clk_prepare_enable(disp->pclk);
> >>
> >> The problem doesn't seem to be in the kernel, but on the TF-A or PMU
> >> firmware side. Have you experienced this by any chance ?
> >
> > Yes, I bumped into the same issue and I used to make a patch (Patch
> > 1) as below.
> >
> > I didn't send it to mainline because it seems not to be a driver issue.
> > The mode of VPLL
> >
> > is not set correctly because:
> >
> > 1) VPLL is enabled before linux
> >
> > 2) linux calling pm_clock_set_pll_mode can't really set register
> > because in ATF
> >
> > it only store the mode value to a structure and wait a clk-enable
> > request to do
> >
> > the register-set operation.
> >
> > 3) linux call clk_enable will not send a clk-enable request since it
> > checks that
> >
> > the VPLL is already hardware-enabled because of 1).
> >
> > So the firmware should disable VPLL when it exits and also in linux
> > zynqmp clk driver
> >
> > there should be a check list to reset some clks to a predefined state.
> >
> >
> > By the way, there is a tiny patch (Patch 2) to fix the black screen
> > issue in DP. I think you may
> >
> > be preparing a big patch which add drm properties to this driver and
> > it may contain this modification,
> >
> > so I didn't send it.
> >
> >
> > Thanks,
> >
> > Quanyang
> >
> > Patch 1:
> >
> > From 93311de2c61e87f2426b89259d81cded71aee673 Mon Sep 17 00:00:00
> 2001
> > From: Quanyang Wang <quanyang.wang at windriver.com>
> > Date: Thu, 3 Dec 2020 19:19:50 +0800
> > Subject: [PATCH 1/3] drm: xlnx: set PLL_MODE_FRAC mode to
> > VPLL_FRAC_CFG by
> > re-enabling disp->pclk
> >
> > When the function clk_set_rate configures the rate of disp->pclk,
> > zynqmp_pm_set_pll_frac_mode will be called to set VPLL's mode to be
> > PLL_MODE_FRAC or PLL_MODE_INT by invoking an SMC call to ATF.
> > But in ATF, the service pm_clock_set_pll_mode doesn't really set the
> > VPLL_FRAC_CFG register but only stores the mode value to struct pm_pll
> > *pll. The operation that sets the register must be triggered by
> > zynqmp_pm_clock_enable.
> >
> > Since disp->pclk is enabled in hardware before linux booting,
> > clk_prepare_enable will skip over zynqmp_pm_clock_enable. So we have
> > to enable then disable disp->pclk, and re-enable it to make sure that
> > zynqmp_pm_clock_enable is triggered and the mode is set to
> > VPLL_FRAC_CFG. Or else VPLL will work in an incorrect mode.
> >
> > Signed-off-by: Quanyang Wang <quanyang.wang at windriver.com>
> > ---
> > drivers/gpu/drm/xlnx/zynqmp_disp.c | 5 +++++
> > 1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/xlnx/zynqmp_disp.c
> > b/drivers/gpu/drm/xlnx/zynqmp_disp.c
> > index 98bd48f13fd1..19753ffc424e 100644
> > --- a/drivers/gpu/drm/xlnx/zynqmp_disp.c
> > +++ b/drivers/gpu/drm/xlnx/zynqmp_disp.c
> > @@ -1668,6 +1668,11 @@ int zynqmp_disp_probe(struct zynqmp_dpsub
> > *dpsub, struct drm_device *drm)
> > dev_err(disp->dev, "failed to init any video clock\n");
> > return PTR_ERR(disp->pclk);
> > }
> > +
> > + /* Make sure that disp->pclk is disabled in hardware */
> > + ret = clk_prepare_enable(disp->pclk);
> > + clk_disable_unprepare(disp->pclk);
> > +
> > disp->pclk_from_ps = true;
> > }
> >
> > Patch 2:
> >
> > From 8c6d36bcb4e79e0e5f8e157446cd994b4a2126f0 Mon Sep 17 00:00:00
> 2001
> > From: Quanyang Wang <quanyang.wang at windriver.com>
> > Date: Thu, 3 Dec 2020 19:32:56 +0800
> > Subject: [PATCH 2/3] drm: xlnx: configure alpha value to make graphic
> > layer
> > opaque
> >
> > Since graphics layer is primary, and video layer is overaly, we need
> > to configure the V_BLEND_SET_GLOBAL_ALPHA_REG register to make graphic
> > layer opaque by default, or else graphic layer will be transparent and
> > invisible.
> >
> > Signed-off-by: Quanyang Wang <quanyang.wang at windriver.com>
> > ---
> > drivers/gpu/drm/xlnx/zynqmp_disp.c | 3 ++-
> > drivers/gpu/drm/xlnx/zynqmp_disp_regs.h | 1 +
> > 2 files changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/xlnx/zynqmp_disp.c
> > b/drivers/gpu/drm/xlnx/zynqmp_disp.c
> > index 19753ffc424e..5c84589e1899 100644
> > --- a/drivers/gpu/drm/xlnx/zynqmp_disp.c
> > +++ b/drivers/gpu/drm/xlnx/zynqmp_disp.c
> > @@ -1468,7 +1468,8 @@ zynqmp_disp_crtc_atomic_enable(struct drm_crtc
> > *crtc,
> > zynqmp_disp_blend_set_output_format(&disp->blend,
> > ZYNQMP_DPSUB_FORMAT_RGB);
> > zynqmp_disp_blend_set_bg_color(&disp->blend, 0, 0, 0);
> > - zynqmp_disp_blend_set_global_alpha(&disp->blend, false, 0);
> > + zynqmp_disp_blend_set_global_alpha(&disp->blend, true,
> > + ZYNQMP_DISP_V_BLEND_SET_GLOBAL_ALPHA_MAX);
> >
> > zynqmp_disp_enable(disp);
> >
> > diff --git a/drivers/gpu/drm/xlnx/zynqmp_disp_regs.h
> > b/drivers/gpu/drm/xlnx/zynqmp_disp_regs.h
> > index f92a006d5070..ef409aca11ad 100644
> > --- a/drivers/gpu/drm/xlnx/zynqmp_disp_regs.h
> > +++ b/drivers/gpu/drm/xlnx/zynqmp_disp_regs.h
> > @@ -22,6 +22,7 @@
> > #define ZYNQMP_DISP_V_BLEND_SET_GLOBAL_ALPHA 0xc
> > #define ZYNQMP_DISP_V_BLEND_SET_GLOBAL_ALPHA_VALUE(n) ((n) << 1)
> > #define ZYNQMP_DISP_V_BLEND_SET_GLOBAL_ALPHA_EN BIT(0)
> > +#define ZYNQMP_DISP_V_BLEND_SET_GLOBAL_ALPHA_MAX 0xff
> > #define ZYNQMP_DISP_V_BLEND_OUTPUT_VID_FMT 0x14
> > #define ZYNQMP_DISP_V_BLEND_OUTPUT_VID_FMT_RGB 0x0
> > #define ZYNQMP_DISP_V_BLEND_OUTPUT_VID_FMT_YCBCR444 0x1
> >
> >>> ---
> >>> drivers/gpu/drm/xlnx/zynqmp_disp.c | 3 ++-
> >>> 1 file changed, 2 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/drivers/gpu/drm/xlnx/zynqmp_disp.c
> >>> b/drivers/gpu/drm/xlnx/zynqmp_disp.c
> >>> index 148add0ca1d6..909e6c265406 100644
> >>> --- a/drivers/gpu/drm/xlnx/zynqmp_disp.c
> >>> +++ b/drivers/gpu/drm/xlnx/zynqmp_disp.c
> >>> @@ -1445,9 +1445,10 @@ zynqmp_disp_crtc_atomic_enable(struct
> >>> drm_crtc *crtc,
> >>> struct drm_display_mode *adjusted_mode =
> >>> &crtc->state->adjusted_mode;
> >>> int ret, vrefresh;
> >>> + pm_runtime_get_sync(disp->dev);
> >>> +
> >>> zynqmp_disp_crtc_setup_clock(crtc, adjusted_mode);
> >>> - pm_runtime_get_sync(disp->dev);
> >>> ret = clk_prepare_enable(disp->pclk);
> >>> if (ret) {
> >>> dev_err(disp->dev, "failed to enable a pixel clock\n");
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