Re: [PATCH v10 5/5] drm/rockchip: Add dmc notifier in vop driver

hl
2016-09-06T18:15:32Z

Hi Sean,

On 2016年09月07日 01:18, Sean Paul wrote:
> On Mon, Sep 5, 2016 at 1:06 AM, Lin Huang <hl@rock-chips.com> 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@rock-chips.com>
>> Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
>> ---
>> 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).
No i use the vop_switch_status and dmc_in_progress to handle the vop
and dmc racey,
I assume this can fix the racey now. I do not better a idea now.
>
>
>> + 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.
Okay, i will check it, thanks.
>
>> + 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
>
>> 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);
>> }
>> }
>>
>> @@ -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
>>
>
>

--
Lin Huang