| Message ID | 20221018-clk-range-checks-fixes-v3-54-9a1358472d52@cerno.tech (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
| Series | clk: Make determine_rate mandatory for muxes | expand |
On 4/4/23 5:11 AM, Maxime Ripard wrote: > The TI DA8xx USB0 clk48 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. > As mentioned in my previous review, parent is selected by device tree and should never be changed after init.
Hi David, On Wed, Apr 05, 2023 at 10:03:24AM -0500, David Lechner wrote: > On 4/4/23 5:11 AM, Maxime Ripard wrote: > > The TI DA8xx USB0 clk48 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. > > > > As mentioned in my previous review, parent is selected by device > tree and should never be changed after init. Great minds think alike then, because the driver implements exactly that, either before or after that patch. That patch makes the current behaviour explicit but doesn't change it in any way. So I guess that means that I can add your Acked-by on the three patches you reviewed with the same message? Maxime
On 4/5/23 10:22 AM, Maxime Ripard wrote: > Hi David, > > On Wed, Apr 05, 2023 at 10:03:24AM -0500, David Lechner wrote: >> On 4/4/23 5:11 AM, Maxime Ripard wrote: >>> The TI DA8xx USB0 clk48 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. >>> >> >> As mentioned in my previous review, parent is selected by device >> tree and should never be changed after init. > > Great minds think alike then, because the driver implements exactly > that, either before or after that patch. > > That patch makes the current behaviour explicit but doesn't change it in > any way. > > So I guess that means that I can add your Acked-by on the three patches > you reviewed with the same message? > > Maxime Yes, preferably with a simplified commit message. Acked-by: David Lechner <david@lechnology.com>
diff --git a/drivers/clk/davinci/da8xx-cfgchip.c b/drivers/clk/davinci/da8xx-cfgchip.c index 4c1cc59bba53..f60c97091818 100644 --- a/drivers/clk/davinci/da8xx-cfgchip.c +++ b/drivers/clk/davinci/da8xx-cfgchip.c @@ -462,10 +462,12 @@ static unsigned long da8xx_usb0_clk48_recalc_rate(struct clk_hw *hw, return 48000000; } -static long da8xx_usb0_clk48_round_rate(struct clk_hw *hw, unsigned long rate, - unsigned long *parent_rate) +static int da8xx_usb0_clk48_determine_rate(struct clk_hw *hw, + struct clk_rate_request *req) { - return 48000000; + req->rate = 48000000; + + return 0; } static int da8xx_usb0_clk48_set_parent(struct clk_hw *hw, u8 index) @@ -494,7 +496,7 @@ static const struct clk_ops da8xx_usb0_clk48_ops = { .disable = da8xx_usb0_clk48_disable, .is_enabled = da8xx_usb0_clk48_is_enabled, .recalc_rate = da8xx_usb0_clk48_recalc_rate, - .round_rate = da8xx_usb0_clk48_round_rate, + .determine_rate = da8xx_usb0_clk48_determine_rate, .set_parent = da8xx_usb0_clk48_set_parent, .get_parent = da8xx_usb0_clk48_get_parent, };
The TI DA8xx USB0 clk48 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/davinci/da8xx-cfgchip.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)