Re: [PATCH 3/7] phy: qcom: qmp-pcie: register second optional PHY AUX clock

[Dmitry Baryshkov]

On Tue, 19 Mar 2024 at 17:10, <neil.armstrong@xxxxxxxxxx> wrote:
>
> On 19/03/2024 15:46, Dmitry Baryshkov wrote:
> > On Tue, 19 Mar 2024 at 16:35, Neil Armstrong <neil.armstrong@xxxxxxxxxx> wrote:
> >>
> >> On 19/03/2024 11:59, Neil Armstrong wrote:
> >>> On 19/03/2024 11:55, Dmitry Baryshkov wrote:
> >>>> On Tue, 19 Mar 2024 at 12:45, Neil Armstrong <neil.armstrong@xxxxxxxxxx> wrote:
> >>>>>
> >>>>> The PCIe Gen4x2 PHY found in the SM8[456]50 SoCs have a second clock,
> >>>>> add the code to register it for PHYs configs that sets a aux_clock_rate.
> >>>>>
> >>>>> In order to get the right clock, add qmp_pcie_clk_hw_get() which uses
> >>>>> the newly introduced QMP_PCIE_PIPE_CLK & QMP_PCIE_PHY_AUX_CLK clock
> >>>>> IDs and also supports the legacy bindings by returning the PIPE clock.
> >>>>>
> >>>>> Signed-off-by: Neil Armstrong <neil.armstrong@xxxxxxxxxx>
> >>>>> ---
> >>>>>    drivers/phy/qualcomm/phy-qcom-qmp-pcie.c | 70 ++++++++++++++++++++++++++++++++
> >>>>>    1 file changed, 70 insertions(+)
> >>>>>
> >>>>> diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> >>>>> index 079b3e306489..2d05226ae200 100644
> >>>>> --- a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> >>>>> +++ b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> >>>>> @@ -22,6 +22,8 @@
> >>>>>    #include <linux/reset.h>
> >>>>>    #include <linux/slab.h>
> >>>>>
> >>>>> +#include <dt-bindings/phy/phy-qcom-qmp.h>
> >>>>> +
> >>>>>    #include "phy-qcom-qmp-common.h"
> >>>>>
> >>>>>    #include "phy-qcom-qmp.h"
> >>>>> @@ -2389,6 +2391,9 @@ struct qmp_phy_cfg {
> >>>>>
> >>>>>           /* QMP PHY pipe clock interface rate */
> >>>>>           unsigned long pipe_clock_rate;
> >>>>> +
> >>>>> +       /* QMP PHY AUX clock interface rate */
> >>>>> +       unsigned long aux_clock_rate;
> >>>>>    };
> >>>>>
> >>>>>    struct qmp_pcie {
> >>>>> @@ -2420,6 +2425,7 @@ struct qmp_pcie {
> >>>>>           int mode;
> >>>>>
> >>>>>           struct clk_fixed_rate pipe_clk_fixed;
> >>>>> +       struct clk_fixed_rate aux_clk_fixed;
> >>>>>    };
> >>>>>
> >>>>>    static inline void qphy_setbits(void __iomem *base, u32 offset, u32 val)
> >>>>> @@ -3681,6 +3687,62 @@ static int phy_pipe_clk_register(struct qmp_pcie *qmp, struct device_node *np)
> >>>>>           return devm_clk_hw_register(qmp->dev, &fixed->hw);
> >>>>>    }
> >>>>>
> >>>>> +/*
> >>>>> + * Register a fixed rate PHY aux clock.
> >>>>> + *
> >>>>> + * The <s>_phy_aux_clksrc generated by PHY goes to the GCC that gate
> >>>>> + * controls it. The <s>_phy_aux_clk coming out of the GCC is requested
> >>>>> + * by the PHY driver for its operations.
> >>>>> + * We register the <s>_phy_aux_clksrc here. The gcc driver takes care
> >>>>> + * of assigning this <s>_phy_aux_clksrc as parent to <s>_phy_aux_clk.
> >>>>> + * Below picture shows this relationship.
> >>>>> + *
> >>>>> + *         +---------------+
> >>>>> + *         |   PHY block   |<<---------------------------------------------+
> >>>>> + *         |               |                                               |
> >>>>> + *         |   +-------+   |                      +-----+                  |
> >>>>> + *   I/P---^-->|  PLL  |---^--->phy_aux_clksrc--->| GCC |--->phy_aux_clk---+
> >>>>> + *    clk  |   +-------+   |                      +-----+
> >>>>> + *         +---------------+
> >>>>> + */
> >>>>> +static int phy_aux_clk_register(struct qmp_pcie *qmp, struct device_node *np)
> >>>>> +{
> >>>>> +       struct clk_fixed_rate *fixed = &qmp->aux_clk_fixed;
> >>>>> +       struct clk_init_data init = { };
> >>>>> +       int ret;
> >>>>> +
> >>>>> +       ret = of_property_read_string_index(np, "clock-output-names", 1, &init.name);
> >>>>> +       if (ret) {
> >>>>> +               dev_err(qmp->dev, "%pOFn: No clock-output-names index 1\n", np);
> >>>>> +               return ret;
> >>>>> +       }
> >>>>> +
> >>>>> +       init.ops = &clk_fixed_rate_ops;
> >>>>> +
> >>>>> +       fixed->fixed_rate = qmp->cfg->aux_clock_rate;
> >>>>> +       fixed->hw.init = &init;
> >>>>> +
> >>>>> +       return devm_clk_hw_register(qmp->dev, &fixed->hw);
> >>>>> +}
> >>>>> +
> >>>>> +static struct clk_hw *qmp_pcie_clk_hw_get(struct of_phandle_args *clkspec, void *data)
> >>>>> +{
> >>>>> +       struct qmp_pcie *qmp = data;
> >>>>> +
> >>>>> +       /* Support legacy bindings */
> >>>>> +       if (!clkspec->args_count)
> >>>>> +               return &qmp->pipe_clk_fixed.hw;
> >>>>> +
> >>>>> +       switch (clkspec->args[0]) {
> >>>>> +       case QMP_PCIE_PIPE_CLK:
> >>>>> +               return &qmp->pipe_clk_fixed.hw;
> >>>>> +       case QMP_PCIE_PHY_AUX_CLK:
> >>>>> +               return &qmp->aux_clk_fixed.hw;
> >>>>> +       }
> >>>>> +
> >>>>> +       return ERR_PTR(-EINVAL);
> >>>>> +}
> >>>>
> >>>> Can we use of_clk_hw_onecell_get() instead? I think it even should be
> >>>> possible to use onecell for both cases, it will look at the first arg,
> >>>> which will be 0 in case of #clock-cells equal to 0.
>
> I didn't find evidence this is the case, while following of_parse_clkspec() called
> from of_clk_get_hw() or clk_core_get(), where clkspec is not initialized, the
> __of_parse_phandle_with_args() and of_phandle_iterator_args() don't touch
> clkspec->args if it->cur_count is 0. So clkspec->args[0] may be left initialized
> and it would be abusingthe API to use it with #clocks-cells = 0.

Ack, true.

>
> >>>
> >>> Let me investigate if it's possible
> >>
> >> Ok, it would work but it would require building a clk_hw_onecell_data a runtime,
> >> while we could simply provide this qmp_pcie_clk_hw_get() and avoid runtime 2 allocations.
> >>
> >> I'm not sure it's worth it.
> >
> > Single allocation (or even 0 allocations if you embed it into struct
> > qmp_pcie) for the sake of using standard helpers.
> >
> Well, sure
>
> Thanks,
> Neil
>


-- 
With best wishes
Dmitry