Re: [PATCH v2 04/22] clk: qcom: smd-rpm: Export clock scaling availability

[Stephan Gerhold]

On Sat, Jun 10, 2023 at 08:53:05PM +0200, Konrad Dybcio wrote:
> On 10.06.2023 14:15, Konrad Dybcio wrote:
> > On 10.06.2023 13:35, Stephan Gerhold wrote:
> >> On Fri, Jun 09, 2023 at 10:19:09PM +0200, Konrad Dybcio wrote:
> >>> Before we issue a call to RPM through clk_smd_rpm_enable_scaling() the
> >>> clock rate requests will not be commited in hardware. This poses a
> >>> race threat since we're accessing the bus clocks directly from within
> >>> the interconnect framework.
> >>>
> >>> Add a marker to indicate that we're good to go with sending new requests
> >>> and export it so that it can be referenced from icc.
> >>>
> >>> Signed-off-by: Konrad Dybcio <konrad.dybcio@xxxxxxxxxx>
> >>> ---
> >>>  drivers/clk/qcom/clk-smd-rpm.c   | 9 +++++++++
> >>>  include/linux/soc/qcom/smd-rpm.h | 2 ++
> >>>  2 files changed, 11 insertions(+)
> >>>
> >>> diff --git a/drivers/clk/qcom/clk-smd-rpm.c b/drivers/clk/qcom/clk-smd-rpm.c
> >>> index 937cb1515968..482fe30ee6f0 100644
> >>> --- a/drivers/clk/qcom/clk-smd-rpm.c
> >>> +++ b/drivers/clk/qcom/clk-smd-rpm.c
> >>> @@ -151,6 +151,7 @@
> >>>  #define to_clk_smd_rpm(_hw) container_of(_hw, struct clk_smd_rpm, hw)
> >>>  
> >>>  static struct qcom_smd_rpm *rpmcc_smd_rpm;
> >>> +static bool smd_rpm_clk_scaling;
> >>>  
> >>>  struct clk_smd_rpm {
> >>>  	const int rpm_res_type;
> >>> @@ -385,6 +386,12 @@ static unsigned long clk_smd_rpm_recalc_rate(struct clk_hw *hw,
> >>>  	return r->rate;
> >>>  }
> >>>  
> >>> +bool qcom_smd_rpm_scaling_available(void)
> >>> +{
> >>> +	return smd_rpm_clk_scaling;
> >>> +}
> >>> +EXPORT_SYMBOL_GPL(qcom_smd_rpm_scaling_available);
> >>> +
> >>>  static int clk_smd_rpm_enable_scaling(void)
> >>>  {
> >>>  	int ret;
> >>> @@ -410,6 +417,8 @@ static int clk_smd_rpm_enable_scaling(void)
> >>>  		return ret;
> >>>  	}
> >>>  
> >>> +	smd_rpm_clk_scaling = true;
> >>> +
> >>
> >> If you move the platform_device_register_data(&rpdev->dev,
> >> "icc_smd_rpm", ...) from drivers/soc/qcom/smd-rpm.c to here you can
> >> avoid the race completely and drop this API. I think that would be
> >> cleaner. And it will likely probe much faster because probe deferral
> >> is slow. :)
> > Sounds like an idea.. especially since it's pretty much the only
> > dependency other than SMDRPM itself!
> It sounds great, but to not break bisecting one has to:
> 
> 1. change the registration in soc/smd-rpm to store rpm ptr in driver
>    data, in addition to parent driver data
> 
> 2. change icc/smd-rpm to use the device and not parent data
> 
> 3. add a platform_device_register_data call in clk-smd-rpm that will
>    always fail because the device is always registered
> 
> 4. remove the registration from soc/smd-rpm
> 

Logically the icc_smd_rpm device still fits better as child of
smd-rpm and not clk-smd-rpm. So I would probably just continue
registering it on the parent device from clk-smd-rpm.
Then there are no changes necessary in icc_smd_rpm.

You could use this. Both touched files are Bjorn-maintained so should be
manageable to have it in one commit. (note: compile-tested only)

Thanks,
Stephan