linux-kernel - Re: [PATCH v3 4/5] phy: qcom-qusb2: Add support for overriding tuning parameters in QUSB2 V2 PHY

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Date:   Fri, 17 Jan 2020 13:46:59 -0800
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Sandeep Maheswaram <sanm@...eaurora.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Stephen Boyd <swboyd@...omium.org>,
        Doug Anderson <dianders@...omium.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, Manu Gautam <mgautam@...eaurora.org>
Subject: Re: [PATCH v3 4/5] phy: qcom-qusb2: Add support for overriding
 tuning parameters in QUSB2 V2 PHY

Hi,

On Fri, Jan 10, 2020 at 05:48:18PM +0530, Sandeep Maheswaram wrote:
> Add support for overriding tuning parameters in QUSB2 V2 PHY
> bias-ctrl-value,charge-ctrl-value and hsdisc-trim-value.
> 
> Signed-off-by: Sandeep Maheswaram <sanm@...eaurora.org>
> ---
>  drivers/phy/qualcomm/phy-qcom-qusb2.c | 51 +++++++++++++++++++++++++++++++++++
>  1 file changed, 51 insertions(+)
> 
> diff --git a/drivers/phy/qualcomm/phy-qcom-qusb2.c b/drivers/phy/qualcomm/phy-qcom-qusb2.c
> index db4ae26..d8bed13 100644
> --- a/drivers/phy/qualcomm/phy-qcom-qusb2.c
> +++ b/drivers/phy/qualcomm/phy-qcom-qusb2.c
> @@ -66,6 +66,14 @@
>  #define IMP_RES_OFFSET_MASK			GENMASK(5, 0)
>  #define IMP_RES_OFFSET_SHIFT			0x0
>  
> +/* QUSB2PHY_PLL_BIAS_CONTROL_2 register bits */
> +#define BIAS_CTRL2_RES_OFFSET_MASK		GENMASK(5, 0)
> +#define BIAS_CTRL2_RES_OFFSET_SHIFT		0x0
> +
> +/* QUSB2PHY_CHG_CONTROL_2 register bits */
> +#define CHG_CTRL2_OFFSET_MASK			GENMASK(5, 4)
> +#define CHG_CTRL2_OFFSET_SHIFT			0x4
> +
>  /* QUSB2PHY_PORT_TUNE1 register bits */
>  #define HSTX_TRIM_MASK				GENMASK(7, 4)
>  #define HSTX_TRIM_SHIFT				0x4
> @@ -73,6 +81,10 @@
>  #define PREEMPHASIS_EN_MASK			GENMASK(1, 0)
>  #define PREEMPHASIS_EN_SHIFT			0x0
>  
> +/* QUSB2PHY_PORT_TUNE2 register bits */
> +#define HSDISC_TRIM_MASK			GENMASK(1, 0)
> +#define HSDISC_TRIM_SHIFT			0x0
> +
>  #define QUSB2PHY_PLL_ANALOG_CONTROLS_TWO	0x04
>  #define QUSB2PHY_PLL_CLOCK_INVERTERS		0x18c
>  #define QUSB2PHY_PLL_CMODE			0x2c
> @@ -327,6 +339,12 @@ struct qusb2_phy {
>  	u8 preemphasis_level;
>  	bool override_preemphasis_width;
>  	u8 preemphasis_width;
> +	bool override_bias_ctrl;
> +	u8 bias_ctrl_value;
> +	bool override_charge_ctrl;
> +	u8 charge_ctrl_value;
> +	bool override_hsdisc_trim;
> +	u8 hsdisc_trim_value;

Documentation for the new struct members is missing.

Given the increasing numbers of overrides you could consider to organize
them in a struct, instead of adding a 'override_' and '_value' to qusb2_phy
for every param. E.g.:

struct override_param {
        bool override;
        u8 value;
};

struct override_params {
        struct override_param imp_res_offset;
        struct override_param hstx_trim;
        ...
};

struct qusb2_phy {
        struct override_params overrides;
};


Or - if you want to take it even further - something along these lines:

struct override_param {
        const char *dt_property;
        u32 offset;
        u8 shift;
        u8 mask;

        // separate struct, since these are not constant?
        bool override;
        u8 value;
};

struct override_param params[] = {
        { "qcom,bias-ctrl-value", QUSB2PHY_PLL_BIAS_CONTROL_2, GENMASK(5, 0), 0 },
        { "qcom,charge-ctrl-value", QUSB2PHY_CHG_CTRL2, GENMASK(5, 4), 4 },
        ...
};