| Message ID | 20221018-clk-range-checks-fixes-v3-46-9a1358472d52@cerno.tech (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | clk: Make determine_rate mandatory for muxes | expand |
On 04.04.2023 13:11, Maxime Ripard wrote: > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe > > The Atmel SAM9x5 SMD clocks implements a mux with a set_parent > hook, but doesn't provide a determine_rate implementation. > > This is a bit odd, since set_parent() is there to, as its name implies, > change the parent of a clock. However, the most likely candidate to > trigger that parent change is a call to clk_set_rate(), with > determine_rate() figuring out which parent is the best suited for a > given rate. > > The other trigger would be a call to clk_set_parent(), but it's far less > used, and it doesn't look like there's any obvious user for that clock. > > So, the set_parent hook is effectively unused, possibly because of an > oversight. However, it could also be an explicit decision by the > original author to avoid any reparenting but through an explicit call to > clk_set_parent(). > > The driver does implement round_rate() though, which means that we can > change the rate of the clock, but we will never get to change the > parent. > > However, It's hard to tell whether it's been done on purpose or not. > > Since we'll start mandating a determine_rate() implementation, let's > convert the round_rate() implementation to a determine_rate(), which > will also make the current behavior explicit. And if it was an > oversight, the clock behaviour can be adjusted later on. > > Signed-off-by: Maxime Ripard <maxime@cerno.tech> Reviewed-by: Claudiu Beznea <claudiu.beznea@microchip.com> Tested-by: Claudiu Beznea <claudiu.beznea@microchip.com> > --- > drivers/clk/at91/clk-smd.c | 29 +++++++++++++++++------------ > 1 file changed, 17 insertions(+), 12 deletions(-) > > diff --git a/drivers/clk/at91/clk-smd.c b/drivers/clk/at91/clk-smd.c > index 160378438f1b..09c649c8598e 100644 > --- a/drivers/clk/at91/clk-smd.c > +++ b/drivers/clk/at91/clk-smd.c > @@ -36,26 +36,31 @@ static unsigned long at91sam9x5_clk_smd_recalc_rate(struct clk_hw *hw, > return parent_rate / (smddiv + 1); > } > > -static long at91sam9x5_clk_smd_round_rate(struct clk_hw *hw, unsigned long rate, > - unsigned long *parent_rate) > +static int at91sam9x5_clk_smd_determine_rate(struct clk_hw *hw, > + struct clk_rate_request *req) > { > unsigned long div; > unsigned long bestrate; > unsigned long tmp; > > - if (rate >= *parent_rate) > - return *parent_rate; > + if (req->rate >= req->best_parent_rate) { > + req->rate = req->best_parent_rate; > + return 0; > + } > > - div = *parent_rate / rate; > - if (div > SMD_MAX_DIV) > - return *parent_rate / (SMD_MAX_DIV + 1); > + div = req->best_parent_rate / req->rate; > + if (div > SMD_MAX_DIV) { > + req->rate = req->best_parent_rate / (SMD_MAX_DIV + 1); > + return 0; > + } > > - bestrate = *parent_rate / div; > - tmp = *parent_rate / (div + 1); > - if (bestrate - rate > rate - tmp) > + bestrate = req->best_parent_rate / div; > + tmp = req->best_parent_rate / (div + 1); > + if (bestrate - req->rate > req->rate - tmp) > bestrate = tmp; > > - return bestrate; > + req->rate = bestrate; > + return 0; > } > > static int at91sam9x5_clk_smd_set_parent(struct clk_hw *hw, u8 index) > @@ -98,7 +103,7 @@ static int at91sam9x5_clk_smd_set_rate(struct clk_hw *hw, unsigned long rate, > > static const struct clk_ops at91sam9x5_smd_ops = { > .recalc_rate = at91sam9x5_clk_smd_recalc_rate, > - .round_rate = at91sam9x5_clk_smd_round_rate, > + .determine_rate = at91sam9x5_clk_smd_determine_rate, > .get_parent = at91sam9x5_clk_smd_get_parent, > .set_parent = at91sam9x5_clk_smd_set_parent, > .set_rate = at91sam9x5_clk_smd_set_rate, > > -- > 2.39.2 >
diff --git a/drivers/clk/at91/clk-smd.c b/drivers/clk/at91/clk-smd.c index 160378438f1b..09c649c8598e 100644 --- a/drivers/clk/at91/clk-smd.c +++ b/drivers/clk/at91/clk-smd.c @@ -36,26 +36,31 @@ static unsigned long at91sam9x5_clk_smd_recalc_rate(struct clk_hw *hw, return parent_rate / (smddiv + 1); } -static long at91sam9x5_clk_smd_round_rate(struct clk_hw *hw, unsigned long rate, - unsigned long *parent_rate) +static int at91sam9x5_clk_smd_determine_rate(struct clk_hw *hw, + struct clk_rate_request *req) { unsigned long div; unsigned long bestrate; unsigned long tmp; - if (rate >= *parent_rate) - return *parent_rate; + if (req->rate >= req->best_parent_rate) { + req->rate = req->best_parent_rate; + return 0; + } - div = *parent_rate / rate; - if (div > SMD_MAX_DIV) - return *parent_rate / (SMD_MAX_DIV + 1); + div = req->best_parent_rate / req->rate; + if (div > SMD_MAX_DIV) { + req->rate = req->best_parent_rate / (SMD_MAX_DIV + 1); + return 0; + } - bestrate = *parent_rate / div; - tmp = *parent_rate / (div + 1); - if (bestrate - rate > rate - tmp) + bestrate = req->best_parent_rate / div; + tmp = req->best_parent_rate / (div + 1); + if (bestrate - req->rate > req->rate - tmp) bestrate = tmp; - return bestrate; + req->rate = bestrate; + return 0; } static int at91sam9x5_clk_smd_set_parent(struct clk_hw *hw, u8 index) @@ -98,7 +103,7 @@ static int at91sam9x5_clk_smd_set_rate(struct clk_hw *hw, unsigned long rate, static const struct clk_ops at91sam9x5_smd_ops = { .recalc_rate = at91sam9x5_clk_smd_recalc_rate, - .round_rate = at91sam9x5_clk_smd_round_rate, + .determine_rate = at91sam9x5_clk_smd_determine_rate, .get_parent = at91sam9x5_clk_smd_get_parent, .set_parent = at91sam9x5_clk_smd_set_parent, .set_rate = at91sam9x5_clk_smd_set_rate,
The Atmel SAM9x5 SMD clocks implements a mux with a set_parent hook, but doesn't provide a determine_rate implementation. This is a bit odd, since set_parent() is there to, as its name implies, change the parent of a clock. However, the most likely candidate to trigger that parent change is a call to clk_set_rate(), with determine_rate() figuring out which parent is the best suited for a given rate. The other trigger would be a call to clk_set_parent(), but it's far less used, and it doesn't look like there's any obvious user for that clock. So, the set_parent hook is effectively unused, possibly because of an oversight. However, it could also be an explicit decision by the original author to avoid any reparenting but through an explicit call to clk_set_parent(). The driver does implement round_rate() though, which means that we can change the rate of the clock, but we will never get to change the parent. However, It's hard to tell whether it's been done on purpose or not. Since we'll start mandating a determine_rate() implementation, let's convert the round_rate() implementation to a determine_rate(), which will also make the current behavior explicit. And if it was an oversight, the clock behaviour can be adjusted later on. Signed-off-by: Maxime Ripard <maxime@cerno.tech> --- drivers/clk/at91/clk-smd.c | 29 +++++++++++++++++------------ 1 file changed, 17 insertions(+), 12 deletions(-)