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

[Dmitry Baryshkov]

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.
> >
> > 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.



-- 
With best wishes
Dmitry