On Wed, Sep 7, 2016 at 1:31 PM, Sean Paul <seanpaul@xxxxxxxxxx> wrote: > On Wed, Sep 7, 2016 at 2:13 PM, dbasehore . <dbasehore@xxxxxxxxxxxx> wrote: >> On Tue, Sep 6, 2016 at 10:18 AM, Sean Paul <seanpaul@xxxxxxxxxx> wrote: >>> On Mon, Sep 5, 2016 at 1:06 AM, Lin Huang <hl@xxxxxxxxxxxxxx> wrote: >>>> when in ddr frequency scaling process, vop can not do enable or >>>> disable operation, since in dcf we check vop clock to see whether >>>> vop work. If vop work, dcf do ddr frequency scaling when vop >>>> in vblank status, and we need to read vop register to check whether >>>> vop go into vblank status. If vop not work, dcf can do ddr frequency >>>> any time. So when do ddr frequency scaling, you disabled or enable >>>> vop, there may two bad thing happen: 1, the panel flicker(when vop from >>>> disable status change to enable). 2, kernel hang (when vop from enable >>>> status change to disable, dcf need to read vblank status, but if you disable >>>> vop clock, it can not get the status, it will lead soc dead) So we need >>>> register to devfreq notifier, and we can get the dmc status. Also, when >>>> there have two vop enabled, we need to disable dmc, since dcf only base >>>> on one vop vblank time, so the other panel will flicker when do ddr >>>> frequency scaling. >>>> >>>> Signed-off-by: Lin Huang <hl@xxxxxxxxxxxxxx> >>>> Reviewed-by: Chanwoo Choi <cw00.choi@xxxxxxxxxxx> >>>> --- >>>> Changes in v10: >>>> - None >>>> >>>> Changes in v9: >>>> - None >>>> >>>> Changes in v8: >>>> - None >>>> >>>> Changes in v7: >>>> - None >>>> >>>> Changes in v6: >>>> - fix a build error >>>> >>>> Changes in v5: >>>> - improve some nits >>>> >>>> Changes in v4: >>>> - register notifier to devfreq_register_notifier >>>> - use DEVFREQ_PRECHANGE and DEVFREQ_POSTCHANGE to get dmc status >>>> - when two vop enable, disable dmc >>>> - when two vop back to one vop, enable dmc >>>> >>>> Changes in v3: >>>> - when do vop eanble/disable, dmc will wait until it finish >>>> >>>> Changes in v2: >>>> - None >>>> >>>> Changes in v1: >>>> - use wait_event instead usleep >>>> >>>> drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 116 ++++++++++++++++++++++++++++ >>>> 1 file changed, 116 insertions(+) >>>> >>>> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c >>>> index efbc41a..a73f3aa 100644 >>>> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c >>>> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c >>>> @@ -19,6 +19,8 @@ >>>> #include <drm/drm_crtc_helper.h> >>>> #include <drm/drm_plane_helper.h> >>>> >>>> +#include <linux/devfreq.h> >>>> +#include <linux/devfreq-event.h> >>>> #include <linux/kernel.h> >>>> #include <linux/module.h> >>>> #include <linux/platform_device.h> >>>> @@ -118,6 +120,13 @@ struct vop { >>>> >>>> const struct vop_data *data; >>>> >>>> + struct devfreq *devfreq; >>>> + struct devfreq_event_dev *devfreq_event_dev; >>>> + struct notifier_block dmc_nb; >>>> + int dmc_in_process; >>>> + int vop_switch_status; >>>> + wait_queue_head_t wait_dmc_queue; >>>> + wait_queue_head_t wait_vop_switch_queue; >>>> uint32_t *regsbak; >>>> void __iomem *regs; >>>> >>>> @@ -428,11 +437,47 @@ static void vop_dsp_hold_valid_irq_disable(struct vop *vop) >>>> spin_unlock_irqrestore(&vop->irq_lock, flags); >>>> } >>>> >>>> +static int dmc_notify(struct notifier_block *nb, unsigned long event, >>>> + void *data) >>>> +{ >>>> + struct vop *vop = container_of(nb, struct vop, dmc_nb); >>>> + >>>> + if (event == DEVFREQ_PRECHANGE) { >>>> + /* >>>> + * check if vop in enable or disable process, >>>> + * if yes, wait until it finishes, use 200ms as >>>> + * timeout. >>>> + */ >>>> + if (!wait_event_timeout(vop->wait_vop_switch_queue, >>>> + !vop->vop_switch_status, HZ / 5)) >>>> + dev_warn(vop->dev, >>>> + "Timeout waiting for vop swtich status\n"); >>>> + vop->dmc_in_process = 1; >>>> + } else if (event == DEVFREQ_POSTCHANGE) { >>>> + vop->dmc_in_process = 0; >>>> + wake_up(&vop->wait_dmc_queue); >>>> + } >>>> + >>>> + return NOTIFY_OK; >>>> +} >>>> + >>>> static int vop_enable(struct drm_crtc *crtc) >>>> { >>>> struct vop *vop = to_vop(crtc); >>>> + int num_enabled_crtc = 0; >>>> int ret; >>>> >>>> + /* >>>> + * if in dmc scaling frequency process, wait until it finishes >>>> + * use 200ms as timeout time. >>>> + */ >>>> + if (!wait_event_timeout(vop->wait_dmc_queue, >>>> + !vop->dmc_in_process, HZ / 5)) >>>> + dev_warn(vop->dev, >>>> + "Timeout waiting for dmc when vop enable\n"); >>>> + >>> >>> >>> This wait_event_timeout code is terribly racey (same goes above and below). >>> >>> >>>> + vop->vop_switch_status = 1; >>>> + >>>> ret = pm_runtime_get_sync(vop->dev); >>>> if (ret < 0) { >>>> dev_err(vop->dev, "failed to get pm runtime: %d\n", ret); >>>> @@ -479,6 +524,21 @@ static int vop_enable(struct drm_crtc *crtc) >>>> >>>> drm_crtc_vblank_on(crtc); >>>> >>>> + vop->vop_switch_status = 0; >>>> + wake_up(&vop->wait_vop_switch_queue); >>>> + >>>> + /* check how many VOPs in use now */ >>>> + drm_for_each_crtc(crtc, vop->drm_dev) { >>>> + if (crtc->state->enable) >>> >>> I think you really want to check active, instead of enable. >>> >>>> + num_enabled_crtc++; >>>> + } >>>> + >>>> + /* if enable two vop, need to disable dmc */ >>>> + if ((num_enabled_crtc > 1) && vop->devfreq) { >>>> + if (vop->devfreq_event_dev) >>>> + devfreq_event_disable_edev(vop->devfreq_event_dev); >>>> + devfreq_suspend_device(vop->devfreq); >>>> + } >>> >>> This really feels like something that should be handled somewhere >>> else. I don't fully understand how this works, but it seems like this >>> dependency should be handled where it actually matters, rather than >>> building in a seemingly arbitrary restriction in the vop driver. >>> >>> Even if this is the best place for it, this needs to be refactored to >>> eliminate the races that exist now. >>> >>> Sean >> >> DMC transitions can't happen when there is more than one display. You >> would have to synchronize with more than one vblank on the DCF (which >> actually changes the DDR frequency), and that's probably not going to >> happen. >> >> If this code should be done somewhere else, it needs to still be able >> to check the number of displays and avoid race conditions with >> displays getting enabled or disabled. I don't know enough about DRM to >> know if that's possible outside of this code. >> > > Yeah, so I suppose that's another race, since we aren't necessarily > guaranteed to be enabling/disabling the crtcs in the order this patch > assumes. > > I think we can probably handle this better by doing this up a level > where we have a more global view of which vops are enabled/disabled > and the order in which they will be processed. > > I'm working on this now, stay tuned. > > Sean > Can there be concurrent calls to vop enable/disable for different displays? If so, we could also hit a race between calculating num_enabled_crtc and calling devfreq_suspend_device. That section might have to be protected by a lock. > > >>> >>>> return 0; >>>> >>>> err_disable_aclk: >>>> @@ -489,17 +549,31 @@ err_disable_hclk: >>>> clk_disable(vop->hclk); >>>> err_put_pm_runtime: >>>> pm_runtime_put_sync(vop->dev); >>>> + vop->vop_switch_status = 0; >>>> + wake_up(&vop->wait_vop_switch_queue); >>>> return ret; >>>> } >>>> >>>> static void vop_crtc_disable(struct drm_crtc *crtc) >>>> { >>>> struct vop *vop = to_vop(crtc); >>>> + int num_enabled_crtc = 0; >>>> int i; >>>> >>>> WARN_ON(vop->event); >>>> >>>> /* >>>> + * if in dmc scaling frequency process, wait until it finish >>>> + * use 200ms as timeout time. >>>> + */ >>>> + if (!wait_event_timeout(vop->wait_dmc_queue, >>>> + !vop->dmc_in_process, HZ / 5)) >>>> + dev_warn(vop->dev, >>>> + "Timeout waiting for dmc when vop disable\n"); >>>> + >>>> + vop->vop_switch_status = 1; >>>> + >>>> + /* >>>> * We need to make sure that all windows are disabled before we >>>> * disable that crtc. Otherwise we might try to scan from a destroyed >>>> * buffer later. >>>> @@ -555,6 +629,24 @@ static void vop_crtc_disable(struct drm_crtc *crtc) >>>> spin_unlock_irq(&crtc->dev->event_lock); >>>> >>>> crtc->state->event = NULL; >>>> + >>>> + vop->vop_switch_status = 0; >>>> + wake_up(&vop->wait_vop_switch_queue); >>>> + >>>> + /* check how many VOPs in use now */ >>>> + drm_for_each_crtc(crtc, vop->drm_dev) { >>>> + if (crtc->state->enable) >>>> + num_enabled_crtc++; >>>> + } >>>> + >>>> + /* >>>> + * if num_enabled_crtc = 1 now, it means 2 vop enabled >>>> + * change to 1 vop enabled need to enable dmc again. >>>> + */ >>>> + if ((num_enabled_crtc == 1) && vop->devfreq) { >>>> + if (vop->devfreq_event_dev) >>>> + devfreq_event_enable_edev(vop->devfreq_event_dev); >>>> + devfreq_resume_device(vop->devfreq); This is the section I'm referring to. >>>> } >>>> } >>>> >>>> @@ -1413,6 +1505,8 @@ static int vop_bind(struct device *dev, struct device *master, void *data) >>>> struct drm_device *drm_dev = data; >>>> struct vop *vop; >>>> struct resource *res; >>>> + struct devfreq *devfreq; >>>> + struct devfreq_event_dev *event_dev; >>>> size_t alloc_size; >>>> int ret, irq; >>>> >>>> @@ -1474,6 +1568,28 @@ static int vop_bind(struct device *dev, struct device *master, void *data) >>>> return ret; >>>> >>>> pm_runtime_enable(&pdev->dev); >>>> + >>>> + init_waitqueue_head(&vop->wait_vop_switch_queue); >>>> + vop->vop_switch_status = 0; >>>> + init_waitqueue_head(&vop->wait_dmc_queue); >>>> + vop->dmc_in_process = 0; >>>> + >>>> + devfreq = devfreq_get_devfreq_by_phandle(dev, 0); >>>> + if (IS_ERR(devfreq)) >>>> + goto out; >>>> + >>>> + vop->devfreq = devfreq; >>>> + vop->dmc_nb.notifier_call = dmc_notify; >>>> + devfreq_register_notifier(vop->devfreq, &vop->dmc_nb, >>>> + DEVFREQ_TRANSITION_NOTIFIER); >>>> + >>>> + event_dev = devfreq_event_get_edev_by_phandle(vop->devfreq->dev.parent, >>>> + 0); >>>> + if (IS_ERR(event_dev)) >>>> + goto out; >>>> + >>>> + vop->devfreq_event_dev = event_dev; >>>> +out: >>>> return 0; >>>> } >>>> >>>> -- >>>> 2.6.6 >>>> -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html