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Date: Tue, 19 Mar 2024 16:10:18 +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 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.
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.
>>>
>>> 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
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