linux-kernel - Re: [PATCH v10 3/5] drm/msm/dp: add support for DP PLL driver

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Message-ID: <28b1f678-ab8f-cf6a-af9f-fcd79131bdc1@linaro.org>
Date:   Sat, 15 Aug 2020 14:45:17 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Tanmay Shah <tanmay@...eaurora.org>
Cc:     swboyd@...omium.org, devicetree@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        robdclark@...il.com, linux-kernel@...r.kernel.org,
        freedreno@...ts.freedesktop.org, seanpaul@...omium.org,
        daniel@...ll.ch, airlied@...ux.ie, aravindh@...eaurora.org,
        abhinavk@...eaurora.org, khsieh@...eaurora.org,
        Chandan Uddaraju <chandanu@...eaurora.org>,
        Vara Reddy <varar@...eaurora.org>
Subject: Re: [PATCH v10 3/5] drm/msm/dp: add support for DP PLL driver

On 15/08/2020 02:22, Tanmay Shah wrote:
> On 2020-08-14 10:05, Dmitry Baryshkov wrote:
>> On 12/08/2020 07:42, Tanmay Shah wrote:
>>> From: Chandan Uddaraju <chandanu@...eaurora.org>
>>>
>>> Add the needed DP PLL specific files to support
>>> display port interface on msm targets.
>>
>> [skipped]
>>
>>> diff --git a/drivers/gpu/drm/msm/dp/dp_pll_private.h 
>>> b/drivers/gpu/drm/msm/dp/dp_pll_private.h
>>> new file mode 100644
>>> index 000000000000..475ba6ed59ab
>>> --- /dev/null
>>> +++ b/drivers/gpu/drm/msm/dp/dp_pll_private.h
>>> @@ -0,0 +1,98 @@
>>> +/* SPDX-License-Identifier: GPL-2.0-only */
>>> +/*
>>> + * Copyright (c) 2016-2020, The Linux Foundation. All rights reserved.
>>> + */
>>> +
>>> +#ifndef __DP_PLL_10NM_H
>>> +#define __DP_PLL_10NM_H
>>> +
>>> +#include "dp_pll.h"
>>> +#include "dp_reg.h"
>>> +
>>> +#define DP_VCO_HSCLK_RATE_1620MHZDIV1000    1620000UL
>>> +#define DP_VCO_HSCLK_RATE_2700MHZDIV1000    2700000UL
>>> +#define DP_VCO_HSCLK_RATE_5400MHZDIV1000    5400000UL
>>> +#define DP_VCO_HSCLK_RATE_8100MHZDIV1000    8100000UL
>>> +
>>> +#define NUM_DP_CLOCKS_MAX            6
>>> +
>>> +#define DP_PHY_PLL_POLL_SLEEP_US        500
>>> +#define DP_PHY_PLL_POLL_TIMEOUT_US        10000
>>> +
>>> +#define DP_VCO_RATE_8100MHZDIV1000        8100000UL
>>> +#define DP_VCO_RATE_9720MHZDIV1000        9720000UL
>>> +#define DP_VCO_RATE_10800MHZDIV1000        10800000UL
>>> +
>>> +struct dp_pll_vco_clk {
>>> +    struct clk_hw hw;
>>> +    unsigned long    rate;        /* current vco rate */
>>> +    u64        min_rate;    /* min vco rate */
>>> +    u64        max_rate;    /* max vco rate */
>>> +    void        *priv;
>>> +};
>>> +
>>> +struct dp_pll_db {
>>
>> This struct should probably go into dp_pll_10nm.c. dp_pll_7nm.c, for
>> example, will use slightly different structure.
>>
> 
> Sure, it sounds good. I will give it try. Thanks!
> 
>>> +    struct msm_dp_pll *base;
>>> +
>>> +    int id;
>>> +    struct platform_device *pdev;
>>> +
>>> +    /* private clocks: */
>>> +    bool fixed_factor_clk[NUM_DP_CLOCKS_MAX];
>>> +    struct clk_hw *hws[NUM_DP_CLOCKS_MAX];
>>
>> Then these two fields can use exact number of clocks rather than
>> NUM_DP_CLOCKS_MAX.
>>
> 
> I didn't get this. I think NUM_DP_CLOCKS_MAX is doing same?

Not exactly. We'd need fixed_factor_clk[4] for 10nm rather than 6. It's 
not that important, just a small nitpick.


>>> +    u32 num_hws;
>>> +
>>> +    /* lane and orientation settings */
>>> +    u8 lane_cnt;
>>> +    u8 orientation;
>>> +
>>> +    /* COM PHY settings */
>>> +    u32 hsclk_sel;
>>> +    u32 dec_start_mode0;
>>> +    u32 div_frac_start1_mode0;
>>> +    u32 div_frac_start2_mode0;
>>> +    u32 div_frac_start3_mode0;
>>> +    u32 integloop_gain0_mode0;
>>> +    u32 integloop_gain1_mode0;
>>> +    u32 vco_tune_map;
>>> +    u32 lock_cmp1_mode0;
>>> +    u32 lock_cmp2_mode0;
>>> +    u32 lock_cmp3_mode0;
>>> +    u32 lock_cmp_en;
>>> +
>>> +    /* PHY vco divider */
>>> +    u32 phy_vco_div;
>>> +    /*
>>> +     * Certain pll's needs to update the same vco rate after resume in
>>> +     * suspend/resume scenario. Cached the vco rate for such plls.
>>> +     */
>>> +    unsigned long    vco_cached_rate;
>>> +    u32        cached_cfg0;
>>> +    u32        cached_cfg1;
>>> +    u32        cached_outdiv;
>>> +
>>> +    uint32_t index;
>>> +};
>>> +
>>> +static inline struct dp_pll_vco_clk *to_dp_vco_hw(struct clk_hw *hw)
>>> +{
>>> +    return container_of(hw, struct dp_pll_vco_clk, hw);
>>> +}
>>> +
>>> +#define to_msm_dp_pll(vco) ((struct msm_dp_pll *)vco->priv)
>>> +
>>> +#define to_dp_pll_db(x)    ((struct dp_pll_db *)x->priv)
>>> +
>>> +int dp_vco_set_rate_10nm(struct clk_hw *hw, unsigned long rate,
>>> +                unsigned long parent_rate);
>>> +unsigned long dp_vco_recalc_rate_10nm(struct clk_hw *hw,
>>> +                unsigned long parent_rate);
>>> +long dp_vco_round_rate_10nm(struct clk_hw *hw, unsigned long rate,
>>> +                unsigned long *parent_rate);
>>> +int dp_vco_prepare_10nm(struct clk_hw *hw);
>>> +void dp_vco_unprepare_10nm(struct clk_hw *hw);
>>> +
>>> +int msm_dp_pll_10nm_init(struct msm_dp_pll *dp_pll, int id);
>>> +void msm_dp_pll_10nm_deinit(struct msm_dp_pll *dp_pll);
>>
>> These functions don't seem to be used outside of dp_pll_10nm. What
>> about making them static?
> 
> I can't declare static to "init" and "deinit" as they are exported to 
> dp_pll.c.
> Rest of them I can move to dp_pll_10nm and then define static.

Please exuse me for not being exact enough. Of course I meant 
dp_vco_FOO_10nm() functions, not init/exit.

BTW: as I'm looking onto 7nm dp pll, which naming would you prefer?

We can have separate DP_PLL_10nm/DP_PLL_7nm namespaces (as DSI PLLs do) 
or I can override only a set of constants (like downstream driver does).

-- 
With best wishes
Dmitry