Re: [PATCH] drm: xlnx: call pm_runtime_get_sync before setting pixel clock
From: quanyang.wang
Date: Tue Mar 16 2021 - 23:02:15 EST
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@xxxxxxxxxxxxx wrote:
From: Quanyang Wang <quanyang.wang@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxx>
Tested-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
---
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@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
---
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");