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SubjectRe: [PATCH v6 27/30] drm/rockchip: psr: Sanitize semantics of allow/disallow API
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On 05.04.2018 11:49, Enric Balletbo i Serra wrote:
> From: Tomasz Figa <tfiga@chromium.org>
>
> Currently both rockchip_drm_psr_activate() and _deactivate() only set the
> boolean "active" flag without actually making sure that hardware state
> complies with it.
>
> Since we are going to extend the usage of this API to properly lock PSR
> for the duration of atomic commits, we change the semantics in following
> way:
> - a counter is used to track the number of disallow requests,
> - PSR is actually disabled in hardware on first disallow request,
> - PSR enable work is scheduled on last disallow request.

I guess you meant "on last allow request".
I think It would be more readable if you replace disallow with inhibit.

>
> The above allows using the API as a way to deterministically synchronize
> PSR state changes with other DRM events, i.e. atomic commits and cursor
> updates. As a nice side effect, the naming is sorted out and we have
> "inhibit" for stopping the software logic and "enable" for hardware
> state.
>
> Signed-off-by: Tomasz Figa <tfiga@chromium.org>
> Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> ---
>
> drivers/gpu/drm/rockchip/analogix_dp-rockchip.c | 4 +-
> drivers/gpu/drm/rockchip/rockchip_drm_psr.c | 57 ++++++++++++++++++-------
> drivers/gpu/drm/rockchip/rockchip_drm_psr.h | 4 +-
> 3 files changed, 46 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/gpu/drm/rockchip/analogix_dp-rockchip.c b/drivers/gpu/drm/rockchip/analogix_dp-rockchip.c
> index 6d45d62466b3..080f05352195 100644
> --- a/drivers/gpu/drm/rockchip/analogix_dp-rockchip.c
> +++ b/drivers/gpu/drm/rockchip/analogix_dp-rockchip.c
> @@ -134,7 +134,7 @@ static int rockchip_dp_poweron_end(struct analogix_dp_plat_data *plat_data)
> {
> struct rockchip_dp_device *dp = to_dp(plat_data);
>
> - return rockchip_drm_psr_activate(&dp->encoder);
> + return rockchip_drm_psr_inhibit_put(&dp->encoder);
> }
>
> static int rockchip_dp_powerdown(struct analogix_dp_plat_data *plat_data)
> @@ -142,7 +142,7 @@ static int rockchip_dp_powerdown(struct analogix_dp_plat_data *plat_data)
> struct rockchip_dp_device *dp = to_dp(plat_data);
> int ret;
>
> - ret = rockchip_drm_psr_deactivate(&dp->encoder);
> + ret = rockchip_drm_psr_inhibit_get(&dp->encoder);
> if (ret != 0)
> return ret;
>
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_psr.c b/drivers/gpu/drm/rockchip/rockchip_drm_psr.c
> index 448c5fde241c..e7e16d92d5a1 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_psr.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_psr.c
> @@ -27,7 +27,7 @@ struct psr_drv {
> struct drm_encoder *encoder;
>
> struct mutex lock;
> - bool active;
> + int inhibit_count;
> bool enabled;
>
> struct delayed_work flush_work;
> @@ -76,7 +76,7 @@ static int psr_set_state_locked(struct psr_drv *psr, bool enable)
> {
> int ret;
>
> - if (!psr->active)
> + if (psr->inhibit_count > 0)
> return -EINVAL;
>
> if (enable == psr->enabled)
> @@ -101,13 +101,18 @@ static void psr_flush_handler(struct work_struct *work)
> }
>
> /**
> - * rockchip_drm_psr_activate - activate PSR on the given pipe
> + * rockchip_drm_psr_inhibit_put - release PSR inhibit on given encoder
> * @encoder: encoder to obtain the PSR encoder
> *
> + * Decrements PSR inhibit count on given encoder. Should be called only
> + * for a PSR inhibit count increment done before. If PSR inhibit counter
> + * reaches zero, PSR flush work is scheduled to make the hardware enter
> + * PSR mode in PSR_FLUSH_TIMEOUT_MS.
> + *
> * Returns:
> * Zero on success, negative errno on failure.
> */
> -int rockchip_drm_psr_activate(struct drm_encoder *encoder)
> +int rockchip_drm_psr_inhibit_put(struct drm_encoder *encoder)
> {
> struct psr_drv *psr = find_psr_by_encoder(encoder);
>
> @@ -115,21 +120,29 @@ int rockchip_drm_psr_activate(struct drm_encoder *encoder)
> return PTR_ERR(psr);
>
> mutex_lock(&psr->lock);
> - psr->active = true;
> + --psr->inhibit_count;

Maybe some WARN on negative value?
With doc fixes:
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>

 --
Regards
Andrzej

> + if (!psr->inhibit_count)
> + mod_delayed_work(system_wq, &psr->flush_work,
> + PSR_FLUSH_TIMEOUT_MS);
> mutex_unlock(&psr->lock);
>
> return 0;
> }
> -EXPORT_SYMBOL(rockchip_drm_psr_activate);
> +EXPORT_SYMBOL(rockchip_drm_psr_inhibit_put);
>
> /**
> - * rockchip_drm_psr_deactivate - deactivate PSR on the given pipe
> + * rockchip_drm_psr_inhibit_get - acquire PSR inhibit on given encoder
> * @encoder: encoder to obtain the PSR encoder
> *
> + * Increments PSR inhibit count on given encoder. This function guarantees
> + * that after it returns PSR is turned off on given encoder and no PSR-related
> + * hardware state change occurs at least until a matching call to
> + * rockchip_drm_psr_inhibit_put() is done.
> + *
> * Returns:
> * Zero on success, negative errno on failure.
> */
> -int rockchip_drm_psr_deactivate(struct drm_encoder *encoder)
> +int rockchip_drm_psr_inhibit_get(struct drm_encoder *encoder)
> {
> struct psr_drv *psr = find_psr_by_encoder(encoder);
>
> @@ -137,15 +150,15 @@ int rockchip_drm_psr_deactivate(struct drm_encoder *encoder)
> return PTR_ERR(psr);
>
> mutex_lock(&psr->lock);
> - psr->active = false;
> - psr->enabled = false;
> + psr_set_state_locked(psr, false);
> + ++psr->inhibit_count;
> mutex_unlock(&psr->lock);
> cancel_delayed_work_sync(&psr->flush_work);
> cancel_work_sync(&psr->disable_work);
>
> return 0;
> }
> -EXPORT_SYMBOL(rockchip_drm_psr_deactivate);
> +EXPORT_SYMBOL(rockchip_drm_psr_inhibit_get);
>
> static void rockchip_drm_do_flush(struct psr_drv *psr)
> {
> @@ -301,6 +314,11 @@ static const struct input_device_id psr_ids[] = {
> * @encoder: encoder that obtain the PSR function
> * @psr_set: call back to set PSR state
> *
> + * The function returns with PSR inhibit counter initialized with one
> + * and the caller (typically encoder driver) needs to call
> + * rockchip_drm_psr_inhibit_put() when it becomes ready to accept PSR
> + * enable request.
> + *
> * Returns:
> * Zero on success, negative errno on failure.
> */
> @@ -322,7 +340,7 @@ int rockchip_drm_psr_register(struct drm_encoder *encoder,
> INIT_WORK(&psr->disable_work, psr_disable_handler);
> mutex_init(&psr->lock);
>
> - psr->active = false;
> + psr->inhibit_count = 1;
> psr->enabled = false;
> psr->encoder = encoder;
> psr->set = psr_set;
> @@ -362,6 +380,11 @@ EXPORT_SYMBOL(rockchip_drm_psr_register);
> * @encoder: encoder that obtain the PSR function
> * @psr_set: call back to set PSR state
> *
> + * It is expected that the PSR inhibit counter is 1 when this function is
> + * called, which corresponds to a state when related encoder has been
> + * disconnected from any CRTCs and its driver called
> + * rockchip_drm_psr_inhibit_get() to stop the PSR logic.
> + *
> * Returns:
> * Zero on success, negative errno on failure.
> */
> @@ -373,10 +396,14 @@ void rockchip_drm_psr_unregister(struct drm_encoder *encoder)
> mutex_lock(&drm_drv->psr_list_lock);
> list_for_each_entry_safe(psr, n, &drm_drv->psr_list, list) {
> if (psr->encoder == encoder) {
> - input_unregister_handler(&psr->input_handler);
> - cancel_delayed_work_sync(&psr->flush_work);
> - cancel_work_sync(&psr->disable_work);
> + /*
> + * Any other value would mean that the encoder
> + * is still in use.
> + */
> + WARN_ON(psr->inhibit_count != 1);
> +
> list_del(&psr->list);
> + input_unregister_handler(&psr->input_handler);
> kfree(psr->input_handler.name);
> kfree(psr);
> }
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_psr.h b/drivers/gpu/drm/rockchip/rockchip_drm_psr.h
> index 06537ee27565..40e026c14168 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_psr.h
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_psr.h
> @@ -18,8 +18,8 @@
> void rockchip_drm_psr_flush_all(struct drm_device *dev);
> int rockchip_drm_psr_flush(struct drm_crtc *crtc);
>
> -int rockchip_drm_psr_activate(struct drm_encoder *encoder);
> -int rockchip_drm_psr_deactivate(struct drm_encoder *encoder);
> +int rockchip_drm_psr_inhibit_put(struct drm_encoder *encoder);
> +int rockchip_drm_psr_inhibit_get(struct drm_encoder *encoder);
>
> int rockchip_drm_psr_register(struct drm_encoder *encoder,
> int (*psr_set)(struct drm_encoder *, bool enable));


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