| Message ID | 1410466706-27386-4-git-send-email-maxime.ripard@free-electrons.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Am Donnerstag, 11. September 2014, 22:18:17 schrieb Maxime Ripard: > The current phase API doesn't look into the actual hardware to get the phase > value, but will rather get it from a variable only set by the set_phase > function. > > This will cause issue when the client driver will never call the set_phase > function, where we can end up having a reported phase that will not match > what the hardware has been programmed to by the bootloader or what phase is > programmed out of reset. > > Add a new get_phase function for the drivers to implement so that we can get > this value. > > Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com> Reviewed-by: Heiko Stuebner <heiko@sntech.de> > --- > drivers/clk/clk.c | 10 ++++++++++ > include/linux/clk-provider.h | 5 +++++ > 2 files changed, 15 insertions(+) > > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c > index d87661af0c72..113d75db371d 100644 > --- a/drivers/clk/clk.c > +++ b/drivers/clk/clk.c > @@ -1934,6 +1934,16 @@ int __clk_init(struct device *dev, struct clk *clk) > clk->accuracy = 0; > > /* > + * Set clk's phase. > + * Since a phase is by definition relative to its parent, just > + * query the current clock phase, or just assume it's in phase. > + */ > + if (clk->ops->get_phase) > + clk->phase = clk->ops->get_phase(clk->hw); > + else > + clk->phase = 0; > + > + /* > * Set clk's rate. The preferred method is to use .recalc_rate. For > * simple clocks and lazy developers the default fallback is to use the > * parent's rate. If a clock doesn't have a parent (or is orphaned) > diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h > index 69b20d4c1e1a..abec961092a7 100644 > --- a/include/linux/clk-provider.h > +++ b/include/linux/clk-provider.h > @@ -130,6 +130,10 @@ struct dentry; > * set then clock accuracy will be initialized to parent accuracy > * or 0 (perfect clock) if clock has no parent. > * > + * @get_phase: Queries the hardware to get the current phase of a clock. > + * Returned values are 0-359 degrees on success, negative > + * error codes on failure. > + * > * @set_phase: Shift the phase this clock signal in degrees specified > * by the second argument. Valid values for degrees are > * 0-359. Return 0 on success, otherwise -EERROR. > @@ -182,6 +186,7 @@ struct clk_ops { > unsigned long parent_rate, u8 index); > unsigned long (*recalc_accuracy)(struct clk_hw *hw, > unsigned long parent_accuracy); > + int (*get_phase)(struct clk_hw *hw); > int (*set_phase)(struct clk_hw *hw, int degrees); > void (*init)(struct clk_hw *hw); > int (*debug_init)(struct clk_hw *hw, struct dentry *dentry); -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Quoting Maxime Ripard (2014-09-11 13:18:17) > The current phase API doesn't look into the actual hardware to get the phase > value, but will rather get it from a variable only set by the set_phase > function. > > This will cause issue when the client driver will never call the set_phase > function, where we can end up having a reported phase that will not match what > the hardware has been programmed to by the bootloader or what phase is > programmed out of reset. > > Add a new get_phase function for the drivers to implement so that we can get > this value. > > Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com> > --- > drivers/clk/clk.c | 10 ++++++++++ > include/linux/clk-provider.h | 5 +++++ > 2 files changed, 15 insertions(+) > > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c > index d87661af0c72..113d75db371d 100644 > --- a/drivers/clk/clk.c > +++ b/drivers/clk/clk.c > @@ -1934,6 +1934,16 @@ int __clk_init(struct device *dev, struct clk *clk) > clk->accuracy = 0; > > /* > + * Set clk's phase. > + * Since a phase is by definition relative to its parent, just > + * query the current clock phase, or just assume it's in phase. > + */ > + if (clk->ops->get_phase) > + clk->phase = clk->ops->get_phase(clk->hw); > + else > + clk->phase = 0; I probably wasn't paying enough attention to this. Based on the coverletter I thought that v3 would introduce something like CLK_GET_PHASE_NOCACHE and stuff that logic into a __clk_get_phase function? Looks like this version of the series doesn't handle phases that can be changed by hardware (e.g. coming out of idle). Correct me if I am wrong, but it looks like we retrieve the phase only once at init and then never again? The rest of the time we rely on clk->phase to always be accurate... Regards, Mike > + > + /* > * Set clk's rate. The preferred method is to use .recalc_rate. For > * simple clocks and lazy developers the default fallback is to use the > * parent's rate. If a clock doesn't have a parent (or is orphaned) > diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h > index 69b20d4c1e1a..abec961092a7 100644 > --- a/include/linux/clk-provider.h > +++ b/include/linux/clk-provider.h > @@ -130,6 +130,10 @@ struct dentry; > * set then clock accuracy will be initialized to parent accuracy > * or 0 (perfect clock) if clock has no parent. > * > + * @get_phase: Queries the hardware to get the current phase of a clock. > + * Returned values are 0-359 degrees on success, negative > + * error codes on failure. > + * > * @set_phase: Shift the phase this clock signal in degrees specified > * by the second argument. Valid values for degrees are > * 0-359. Return 0 on success, otherwise -EERROR. > @@ -182,6 +186,7 @@ struct clk_ops { > unsigned long parent_rate, u8 index); > unsigned long (*recalc_accuracy)(struct clk_hw *hw, > unsigned long parent_accuracy); > + int (*get_phase)(struct clk_hw *hw); > int (*set_phase)(struct clk_hw *hw, int degrees); > void (*init)(struct clk_hw *hw); > int (*debug_init)(struct clk_hw *hw, struct dentry *dentry); > -- > 2.1.0 > -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Mike, On Sat, Sep 27, 2014 at 05:17:32PM -0700, Mike Turquette wrote: > Quoting Maxime Ripard (2014-09-11 13:18:17) > > The current phase API doesn't look into the actual hardware to get the phase > > value, but will rather get it from a variable only set by the set_phase > > function. > > > > This will cause issue when the client driver will never call the set_phase > > function, where we can end up having a reported phase that will not match what > > the hardware has been programmed to by the bootloader or what phase is > > programmed out of reset. > > > > Add a new get_phase function for the drivers to implement so that we can get > > this value. > > > > Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com> > > --- > > drivers/clk/clk.c | 10 ++++++++++ > > include/linux/clk-provider.h | 5 +++++ > > 2 files changed, 15 insertions(+) > > > > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c > > index d87661af0c72..113d75db371d 100644 > > --- a/drivers/clk/clk.c > > +++ b/drivers/clk/clk.c > > @@ -1934,6 +1934,16 @@ int __clk_init(struct device *dev, struct clk *clk) > > clk->accuracy = 0; > > > > /* > > + * Set clk's phase. > > + * Since a phase is by definition relative to its parent, just > > + * query the current clock phase, or just assume it's in phase. > > + */ > > + if (clk->ops->get_phase) > > + clk->phase = clk->ops->get_phase(clk->hw); > > + else > > + clk->phase = 0; > > I probably wasn't paying enough attention to this. Based on the > coverletter I thought that v3 would introduce something like > CLK_GET_PHASE_NOCACHE and stuff that logic into a __clk_get_phase > function? Looks like this version of the series doesn't handle phases > that can be changed by hardware (e.g. coming out of idle). > > Correct me if I am wrong, but it looks like we retrieve the phase only > once at init and then never again? The rest of the time we rely on > clk->phase to always be accurate... Yeah, I didn't have any use for it at the moment, and thought that if someone ever needed it, it would be trivial to add, so I left it out. If you want me to still do it, I can send an additional patch. Thanks! Maxime
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index d87661af0c72..113d75db371d 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -1934,6 +1934,16 @@ int __clk_init(struct device *dev, struct clk *clk) clk->accuracy = 0; /* + * Set clk's phase. + * Since a phase is by definition relative to its parent, just + * query the current clock phase, or just assume it's in phase. + */ + if (clk->ops->get_phase) + clk->phase = clk->ops->get_phase(clk->hw); + else + clk->phase = 0; + + /* * Set clk's rate. The preferred method is to use .recalc_rate. For * simple clocks and lazy developers the default fallback is to use the * parent's rate. If a clock doesn't have a parent (or is orphaned) diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h index 69b20d4c1e1a..abec961092a7 100644 --- a/include/linux/clk-provider.h +++ b/include/linux/clk-provider.h @@ -130,6 +130,10 @@ struct dentry; * set then clock accuracy will be initialized to parent accuracy * or 0 (perfect clock) if clock has no parent. * + * @get_phase: Queries the hardware to get the current phase of a clock. + * Returned values are 0-359 degrees on success, negative + * error codes on failure. + * * @set_phase: Shift the phase this clock signal in degrees specified * by the second argument. Valid values for degrees are * 0-359. Return 0 on success, otherwise -EERROR. @@ -182,6 +186,7 @@ struct clk_ops { unsigned long parent_rate, u8 index); unsigned long (*recalc_accuracy)(struct clk_hw *hw, unsigned long parent_accuracy); + int (*get_phase)(struct clk_hw *hw); int (*set_phase)(struct clk_hw *hw, int degrees); void (*init)(struct clk_hw *hw); int (*debug_init)(struct clk_hw *hw, struct dentry *dentry);
The current phase API doesn't look into the actual hardware to get the phase value, but will rather get it from a variable only set by the set_phase function. This will cause issue when the client driver will never call the set_phase function, where we can end up having a reported phase that will not match what the hardware has been programmed to by the bootloader or what phase is programmed out of reset. Add a new get_phase function for the drivers to implement so that we can get this value. Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com> --- drivers/clk/clk.c | 10 ++++++++++ include/linux/clk-provider.h | 5 +++++ 2 files changed, 15 insertions(+)