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    SubjectRe: [PATCH v7 3/6] clk: qcom: gdsc: Add a reset op to poll gdsc collapse
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    On 12/7/2022 9:15 PM, Ulf Hansson wrote:
    > On Wed, 5 Oct 2022 at 11:08, Akhil P Oommen <quic_akhilpo@quicinc.com> wrote:
    >> Add a reset op compatible function to poll for gdsc collapse. This is
    >> required because:
    >> 1. We don't wait for it to turn OFF at hardware for VOTABLE GDSCs.
    >> 2. There is no way for client drivers (eg. gpu driver) to do
    >> put-with-wait for these gdscs which is required in some scenarios
    >> (eg. GPU recovery).
    > What puzzles me a bit, who is the typical consumer of the reset.
    >
    > I looked at patch4 and tried to figure it out, but let's discuss that
    > in that thread instead. Some more comments, see below.

    https://patchwork.freedesktop.org/patch/498397/
    gpu driver side changes are already merged in upstream. We call this interface during a GPU recovery which is supposed to be a rare event.
    >
    >> Signed-off-by: Akhil P Oommen <quic_akhilpo@quicinc.com>
    >> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
    >> ---
    >>
    >> Changes in v7:
    >> - Update commit message (Bjorn)
    >>
    >> Changes in v2:
    >> - Minor update to function prototype
    >>
    >> drivers/clk/qcom/gdsc.c | 23 +++++++++++++++++++----
    >> drivers/clk/qcom/gdsc.h | 7 +++++++
    >> 2 files changed, 26 insertions(+), 4 deletions(-)
    >>
    >> diff --git a/drivers/clk/qcom/gdsc.c b/drivers/clk/qcom/gdsc.c
    >> index 7cf5e13..ccef742 100644
    >> --- a/drivers/clk/qcom/gdsc.c
    >> +++ b/drivers/clk/qcom/gdsc.c
    >> @@ -17,6 +17,7 @@
    >> #include <linux/reset-controller.h>
    >> #include <linux/slab.h>
    >> #include "gdsc.h"
    >> +#include "reset.h"
    >>
    >> #define PWR_ON_MASK BIT(31)
    >> #define EN_REST_WAIT_MASK GENMASK_ULL(23, 20)
    >> @@ -116,7 +117,8 @@ static int gdsc_hwctrl(struct gdsc *sc, bool en)
    >> return regmap_update_bits(sc->regmap, sc->gdscr, HW_CONTROL_MASK, val);
    >> }
    >>
    >> -static int gdsc_poll_status(struct gdsc *sc, enum gdsc_status status)
    >> +static int gdsc_poll_status(struct gdsc *sc, enum gdsc_status status,
    >> + s64 timeout_us, unsigned int interval_ms)
    >> {
    >> ktime_t start;
    >>
    >> @@ -124,7 +126,9 @@ static int gdsc_poll_status(struct gdsc *sc, enum gdsc_status status)
    >> do {
    >> if (gdsc_check_status(sc, status))
    >> return 0;
    >> - } while (ktime_us_delta(ktime_get(), start) < TIMEOUT_US);
    >> + if (interval_ms)
    >> + msleep(interval_ms);
    >> + } while (ktime_us_delta(ktime_get(), start) < timeout_us);
    > Rather than continue to open code this polling loop, would it not make
    > sense to convert the code into using readx_poll_timeout() (or some of
    > its friends).
    I was going for a minimal code churn to get this mainlined easily. I like the idea, perhaps we can have a refactor patch if there is consensus.

    -Akhil.
    >
    > Down the road, this leads to that the msleep() above should become
    > usleep_range() instead, which seems more correct to me.
    >
    >> if (gdsc_check_status(sc, status))
    >> return 0;
    >> @@ -189,7 +193,7 @@ static int gdsc_toggle_logic(struct gdsc *sc, enum gdsc_status status)
    >> udelay(1);
    >> }
    >>
    >> - ret = gdsc_poll_status(sc, status);
    >> + ret = gdsc_poll_status(sc, status, TIMEOUT_US, 0);
    >> WARN(ret, "%s status stuck at 'o%s'", sc->pd.name, status ? "ff" : "n");
    >>
    >> if (!ret && status == GDSC_OFF && sc->rsupply) {
    >> @@ -360,7 +364,7 @@ static int _gdsc_disable(struct gdsc *sc)
    >> */
    >> udelay(1);
    >>
    >> - ret = gdsc_poll_status(sc, GDSC_ON);
    >> + ret = gdsc_poll_status(sc, GDSC_ON, TIMEOUT_US, 0);
    >> if (ret)
    >> return ret;
    >> }
    >> @@ -608,3 +612,14 @@ int gdsc_gx_do_nothing_enable(struct generic_pm_domain *domain)
    >> return 0;
    >> }
    >> EXPORT_SYMBOL_GPL(gdsc_gx_do_nothing_enable);
    >> +
    >> +int gdsc_wait_for_collapse(void *priv)
    >> +{
    >> + struct gdsc *sc = priv;
    >> + int ret;
    >> +
    >> + ret = gdsc_poll_status(sc, GDSC_OFF, 500000, 5);
    >> + WARN(ret, "%s status stuck at 'on'", sc->pd.name);
    >> + return ret;
    >> +}
    >> +EXPORT_SYMBOL_GPL(gdsc_wait_for_collapse);
    >> diff --git a/drivers/clk/qcom/gdsc.h b/drivers/clk/qcom/gdsc.h
    >> index 981a12c..5395f69 100644
    >> --- a/drivers/clk/qcom/gdsc.h
    >> +++ b/drivers/clk/qcom/gdsc.h
    >> @@ -12,6 +12,7 @@
    >> struct regmap;
    >> struct regulator;
    >> struct reset_controller_dev;
    >> +struct qcom_reset_map;
    >>
    >> /**
    >> * struct gdsc - Globally Distributed Switch Controller
    >> @@ -88,6 +89,7 @@ int gdsc_register(struct gdsc_desc *desc, struct reset_controller_dev *,
    >> struct regmap *);
    >> void gdsc_unregister(struct gdsc_desc *desc);
    >> int gdsc_gx_do_nothing_enable(struct generic_pm_domain *domain);
    >> +int gdsc_wait_for_collapse(void *priv);
    >> #else
    >> static inline int gdsc_register(struct gdsc_desc *desc,
    >> struct reset_controller_dev *rcdev,
    >> @@ -97,5 +99,10 @@ static inline int gdsc_register(struct gdsc_desc *desc,
    >> }
    >>
    >> static inline void gdsc_unregister(struct gdsc_desc *desc) {};
    >> +
    >> +static int gdsc_wait_for_collapse(void *priv)
    >> +{
    >> + return -ENOSYS;
    >> +}
    >> #endif /* CONFIG_QCOM_GDSC */
    >> #endif /* __QCOM_GDSC_H__ */
    > Kind regards
    > Uffe

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