linux-kernel - Re: [PATCH 07/10] clk: qcom: Add graphics clock controller driver for SM8150

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Date:   Wed, 27 May 2020 01:44:00 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Jonathan Marek <jonathan@...ek.ca>, linux-arm-msm@...r.kernel.org
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org
Subject: Re: [PATCH 07/10] clk: qcom: Add graphics clock controller driver for SM8150

Quoting Jonathan Marek (2020-05-24 14:06:08)
> diff --git a/drivers/clk/qcom/gpucc-sm8150.c b/drivers/clk/qcom/gpucc-sm8150.c
> new file mode 100644
> index 000000000000..6e1fff0cde75
> --- /dev/null
> +++ b/drivers/clk/qcom/gpucc-sm8150.c
> @@ -0,0 +1,429 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2017-2020, The Linux Foundation. All rights reserved.
> + */
> +
> +#include <linux/clk-provider.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +
> +#include <dt-bindings/clock/qcom,gpucc-sm8150.h>
[..]
> +
> +static struct clk_rcg2 gpu_cc_gmu_clk_src = {
> +       .cmd_rcgr = 0x1120,
> +       .mnd_width = 0,
> +       .hid_width = 5,
> +       .parent_map = gpu_cc_parent_map_0,
> +       .freq_tbl = ftbl_gpu_cc_gmu_clk_src,
> +       .clkr.hw.init = &(struct clk_init_data){
> +               .name = "gpu_cc_gmu_clk_src",
> +               .parent_names = gpu_cc_parent_names_0,
> +               .num_parents = 6,
> +               .flags = CLK_SET_RATE_PARENT,
> +               .ops = &clk_rcg2_ops,
> +       },
> +};
> +
> +static struct clk_branch gpu_cc_ahb_clk = {
> +       .halt_reg = 0x1078,
> +       .halt_check = BRANCH_HALT_DELAY,
> +       .clkr = {
> +               .enable_reg = 0x1078,
> +               .enable_mask = BIT(0),
> +               .hw.init = &(struct clk_init_data){
> +                       .name = "gpu_cc_ahb_clk",
> +                       .flags = CLK_IS_CRITICAL,

Why is this CLK_IS_CRITICAL? Why not just enable the clk manually with
a register write in probe and then remove this clk from the system? We
can save some memory that way.

> +                       .ops = &clk_branch2_ops,
> +               },
> +       },
> +};
> +
[...]
> +
> +static struct gdsc gpu_cx_gdsc = {
> +       .gdscr = 0x106c,
> +       .gds_hw_ctrl = 0x1540,
> +       .pd = {
> +               .name = "gpu_cx_gdsc",
> +       },
> +       .pwrsts = PWRSTS_OFF_ON,
> +       .flags = VOTABLE,
> +};
> +
> +/* see comment in gpucc-sdm845 about this */
> +static int gx_gdsc_enable(struct generic_pm_domain *domain)
> +{
> +       /* Do nothing but give genpd the impression that we were successful */
> +       return 0;
> +}

Maybe we should export a helper from gdsc.c for this with the comment
and it named something obvious? gx_gdsc_do_nothing_enable()?

> +
> +static struct gdsc gpu_gx_gdsc = {
> +       .gdscr = 0x100c,
> +       .clamp_io_ctrl = 0x1508,
> +       .pd = {
> +               .name = "gpu_gx_gdsc",
> +               .power_on = gx_gdsc_enable,
> +       },
> +       .pwrsts = PWRSTS_OFF_ON,
> +       .flags = CLAMP_IO | AON_RESET | POLL_CFG_GDSCR,
> +};
> +