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Date: Tue, 19 Mar 2024 17:45:23 +0100
From: neil.armstrong@...aro.org
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Bjorn Andersson <andersson@...nel.org>,
Konrad Dybcio <konrad.dybcio@...aro.org>, Vinod Koul <vkoul@...nel.org>,
Kishon Vijay Abraham I <kishon@...nel.org>, Rob Herring <robh@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Conor Dooley <conor+dt@...nel.org>, linux-arm-msm@...r.kernel.org,
linux-phy@...ts.infradead.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/7] phy: qcom: qmp-pcie: register second optional PHY AUX
clock
On 19/03/2024 17:05, Dmitry Baryshkov wrote:
> On Tue, 19 Mar 2024 at 17:15, <neil.armstrong@...aro.org> wrote:
>>
>> On 19/03/2024 15:46, Dmitry Baryshkov wrote:
>>> On Tue, 19 Mar 2024 at 16:35, Neil Armstrong <neil.armstrong@...aro.org> 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@...aro.org> 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@...aro.org>
>>>>>>> ---
>>>>>>> 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.
>>
>> And I just recall I tried the same for Amlogic clocks, but the clk_hw_onecell_data hws
>> field is a flexible array member you can't set at runtime, if you try you'll get:
>> drivers/phy/qualcomm/phy-qcom-qmp-pcie.c:3753:38: error: invalid use of flexible array member
>> 3753 | qmp->clk_hw_data.hws = qmp->clk_hws;
>
> Yes, so it's either
> devm_kzalloc(dev, struct_size(data, hws, 2), GFP_KERNEL);
> or
> struct qmp_pcie {
> ...
> struct {
> struct clk_hw_onecell_data clk_data;
> struct clk_hw clocks[2];
> };
> };
I won't go down this path because of that mess and using of_clk_hw_onecell_get() would need
to still add a custom getter before calling of_clk_hw_onecell_get() to handle the
#clock-cells=0 legacy case.
Neil
>
>>
>> Neil
>>
>>>
>>>
>>>
>>
>
>
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