Re: [v11 2/2] clk: ls1028a: Add clock driver for Display output interface

[Stephen Boyd <sboyd@kernel.org>]

Quoting Wen He (2019-12-04 23:26:53)
> Add clock driver for QorIQ LS1028A Display output interfaces(LCD, DPHY),
> as implemented in TSMC CLN28HPM PLL, this PLL supports the programmable
> integer division and range of the display output pixel clock's 27-594MHz.
> 
> Signed-off-by: Wen He <wen.he_1@nxp.com>
> Signed-off-by: Michael Walle <michael@walle.cc>

Is Michael the author? SoB chain is backwards here.

> diff --git a/drivers/clk/clk-plldig.c b/drivers/clk/clk-plldig.c
> new file mode 100644
> index 000000000000..1942686f0254
> --- /dev/null
> +++ b/drivers/clk/clk-plldig.c
> @@ -0,0 +1,297 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright 2019 NXP
> + *
> + * Clock driver for LS1028A Display output interfaces(LCD, DPHY).
> + */
> +
> +#include <linux/clk-provider.h>
> +#include <linux/device.h>
> +#include <linux/module.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/iopoll.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +#include <linux/bitfield.h>
> +
> +/* PLLDIG register offsets and bit masks */
> +#define PLLDIG_REG_PLLSR            0x24
> +#define PLLDIG_LOCK_MASK            BIT(2)
> +#define PLLDIG_REG_PLLDV            0x28
> +#define PLLDIG_MFD_MASK             GENMASK(7, 0)
> +#define PLLDIG_RFDPHI1_MASK         GENMASK(30, 25)
> +#define PLLDIG_REG_PLLFM            0x2c
> +#define PLLDIG_SSCGBYP_ENABLE       BIT(30)
> +#define PLLDIG_REG_PLLFD            0x30
> +#define PLLDIG_FDEN                 BIT(30)
> +#define PLLDIG_FRAC_MASK            GENMASK(15, 0)
> +#define PLLDIG_REG_PLLCAL1          0x38
> +#define PLLDIG_REG_PLLCAL2          0x3c
> +
> +/* Range of the VCO frequencies, in Hz */
> +#define PLLDIG_MIN_VCO_FREQ         650000000
> +#define PLLDIG_MAX_VCO_FREQ         1300000000
> +
> +/* Range of the output frequencies, in Hz */
> +#define PHI1_MIN_FREQ               27000000
> +#define PHI1_MAX_FREQ               600000000
> +
> +/* Maximum value of the reduced frequency divider */
> +#define MAX_RFDPHI1          63UL
> +
> +/* Best value of multiplication factor divider */
> +#define PLLDIG_DEFAULT_MFD   44
> +
> +/*
> + * Denominator part of the fractional part of the
> + * loop multiplication factor.
> + */
> +#define MFDEN          20480
> +
> +static const struct clk_parent_data parent_data[] = {
> +       {.index = 0},

Nitpick: Add spaces after { and before }

> +};
> +
> +struct clk_plldig {
> +       struct clk_hw hw;
> +       void __iomem *regs;
> +       unsigned int vco_freq;
> +};
> +
> +#define to_clk_plldig(_hw)     container_of(_hw, struct clk_plldig, hw)
> +
> +static int plldig_enable(struct clk_hw *hw)
> +{
> +       struct clk_plldig *data = to_clk_plldig(hw);
> +       u32 val;
> +
> +       val = readl(data->regs + PLLDIG_REG_PLLFM);
> +       /*
> +        * Use Bypass mode with PLL off by default, the frequency overshoot
> +        * detector output was disable. SSCG Bypass mode should be enable.
> +        */
> +       val |= PLLDIG_SSCGBYP_ENABLE;
> +       writel(val, data->regs + PLLDIG_REG_PLLFM);
> +
> +       return 0;
> +}
> +
> +static void plldig_disable(struct clk_hw *hw)
> +{
> +       struct clk_plldig *data = to_clk_plldig(hw);
> +       u32 val;
> +
> +       val = readl(data->regs + PLLDIG_REG_PLLFM);
> +
> +       val &= ~PLLDIG_SSCGBYP_ENABLE;
> +       val |= FIELD_PREP(PLLDIG_SSCGBYP_ENABLE, 0x0);
> +
> +       writel(val, data->regs + PLLDIG_REG_PLLFM);
> +}
> +
> +static int plldig_is_enabled(struct clk_hw *hw)
> +{
> +       struct clk_plldig *data = to_clk_plldig(hw);
> +
> +       return (readl(data->regs + PLLDIG_REG_PLLFM) &

Please drop useless parenthesis.

> +                             PLLDIG_SSCGBYP_ENABLE);
> +}
> +
> +static unsigned long plldig_recalc_rate(struct clk_hw *hw,
> +                                       unsigned long parent_rate)
> +{
> +       struct clk_plldig *data = to_clk_plldig(hw);
> +       u32 val, rfdphi1;
> +
> +       val = readl(data->regs + PLLDIG_REG_PLLDV);
> +
> +       /* Check if PLL is bypassed */
> +       if (val & PLLDIG_SSCGBYP_ENABLE)
> +               return parent_rate;
> +
> +       rfdphi1 = FIELD_GET(PLLDIG_RFDPHI1_MASK, val);
> +
> +       /*
> +        * If RFDPHI1 has a value of 1 the VCO frequency is also divided by
> +        * one.
> +        */
> +       if (!rfdphi1)
> +               rfdphi1 = 1;
> +
> +       return DIV_ROUND_UP(data->vco_freq, rfdphi1);
> +}
> +
> +static unsigned long plldig_calc_target_div(unsigned long vco_freq,
> +                                           unsigned long target_rate)
> +{
> +       unsigned long div;
> +
> +       div = DIV_ROUND_CLOSEST(vco_freq, target_rate);
> +       div = max(1UL, div);
> +       div = min(div, MAX_RFDPHI1);

Use clamp().

> +
> +       return div;
> +}
> +
> +static int plldig_determine_rate(struct clk_hw *hw,
> +                                struct clk_rate_request *req)
> +{
> +       struct clk_plldig *data = to_clk_plldig(hw);
> +       unsigned int div;
> +
> +       if (req->rate < PHI1_MIN_FREQ)
> +               req->rate = PHI1_MIN_FREQ;
> +       if (req->rate > PHI1_MAX_FREQ)
> +               req->rate = PHI1_MAX_FREQ;

Use clamp()

> +
> +       div = plldig_calc_target_div(data->vco_freq, req->rate);
> +       req->rate = DIV_ROUND_UP(data->vco_freq, div);
> +
> +       return 0;
> +}
> +
> +static int plldig_set_rate(struct clk_hw *hw, unsigned long rate,
> +               unsigned long parent_rate)
> +{
> +       struct clk_plldig *data = to_clk_plldig(hw);
> +       unsigned int val, cond;
> +       unsigned int rfdphi1;
> +
> +       if (rate < PHI1_MIN_FREQ)
> +               rate = PHI1_MIN_FREQ;
> +       if (rate > PHI1_MAX_FREQ)
> +               rate = PHI1_MAX_FREQ;

Use clamp()

> +
> +       rfdphi1 = plldig_calc_target_div(data->vco_freq, rate);
> +
> +       /* update the divider value */
> +       val = readl(data->regs + PLLDIG_REG_PLLDV);
> +       val &= ~PLLDIG_RFDPHI1_MASK;
> +       val |= FIELD_PREP(PLLDIG_RFDPHI1_MASK, rfdphi1);
> +       writel(val, data->regs + PLLDIG_REG_PLLDV);
> +
> +       /* delay 200us make sure that old lock state is cleared */
> +       udelay(200);

Please remove 'delay 200us' from the comment. Just say that we're waiting
for old lock state to clear. It's clear from the code how much time it
is.

> +
> +       /* Wait until PLL is locked or timeout (maximum 1000 usecs) */

Drop the time. It's a millisecond.

> +       return readl_poll_timeout_atomic(data->regs + PLLDIG_REG_PLLSR, cond,
> +                                        cond & PLLDIG_LOCK_MASK, 0,
> +                                        USEC_PER_MSEC);
> +}
> +
> +static const struct clk_ops plldig_clk_ops = {
> +       .enable = plldig_enable,
> +       .disable = plldig_disable,
> +       .is_enabled = plldig_is_enabled,
> +       .recalc_rate = plldig_recalc_rate,
> +       .determine_rate = plldig_determine_rate,
> +       .set_rate = plldig_set_rate,
> +};
> +
> +static int plldig_init(struct clk_hw *hw)
> +{
> +       struct clk_plldig *data = to_clk_plldig(hw);
> +       struct clk_hw *parent = clk_hw_get_parent(hw);
> +       unsigned long parent_rate = clk_hw_get_rate(parent);
> +       unsigned long val;
> +       unsigned long long lltmp;
> +       unsigned int mfd, fracdiv = 0;
> +
> +       if (!parent)
> +               return -EINVAL;
> +
> +       if (data->vco_freq) {
> +               mfd = data->vco_freq / parent_rate;
> +               lltmp = data->vco_freq % parent_rate;
> +               lltmp *= MFDEN;
> +               do_div(lltmp, parent_rate);
> +               fracdiv = lltmp;
> +       } else {
> +               mfd = PLLDIG_DEFAULT_MFD;
> +               data->vco_freq = parent_rate * mfd;
> +       }
> +
> +       val = FIELD_PREP(PLLDIG_MFD_MASK, mfd);
> +       writel(val, data->regs + PLLDIG_REG_PLLDV);
> +
> +       if (fracdiv) {
> +               val = FIELD_PREP(PLLDIG_FRAC_MASK, fracdiv);
> +               /* Enable fractional divider */

Remove useless comment please. Or move above the if condition.

> +               val |= PLLDIG_FDEN;
> +               writel(val, data->regs + PLLDIG_REG_PLLFD);
> +       }
> +
> +       return 0;
> +}
> +
> +static int plldig_clk_probe(struct platform_device *pdev)
> +{
> +       struct clk_plldig *data;
> +       struct resource *mem;
> +       struct device *dev = &pdev->dev;
> +       int ret;
> +
> +       data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
> +       if (!data)
> +               return -ENOMEM;
> +
> +       mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +       data->regs = devm_ioremap_resource(dev, mem);

We have devm_platform_ioremap_resource() for this now.

> +       if (IS_ERR(data->regs))
> +               return PTR_ERR(data->regs);
> +
> +       data->hw.init = CLK_HW_INIT_PARENTS_DATA("dpclk",
> +                                                parent_data,
> +                                                &plldig_clk_ops,
> +                                                0);
> +
> +       ret = devm_clk_hw_register(dev, &data->hw);
> +       if (ret) {
> +               dev_err(dev, "failed to register %s clock\n",
> +                                               dev->of_node->name);
> +               return ret;
> +       }
> +
> +       ret = devm_of_clk_add_hw_provider(dev, of_clk_hw_simple_get,
> +                                         &data->hw);
> +       if (ret) {
> +               dev_err(dev, "unable to add clk provider\n");
> +               return ret;
> +       }
> +
> +       /*
> +        * The frequency of the VCO cannot be changed during runtime.
> +        * Therefore, let the user specify a desired frequency.
> +        */
> +       if (!of_property_read_u32(dev->of_node, "fsl,vco-hz",
> +                                 &data->vco_freq)) {
> +               if (data->vco_freq < PLLDIG_MIN_VCO_FREQ ||
> +                   data->vco_freq > PLLDIG_MAX_VCO_FREQ)
> +                       return -EINVAL;
> +       }
> +
> +       return plldig_init(&data->hw);
> +}
> +
> +static const struct of_device_id plldig_clk_id[] = {
> +       { .compatible = "fsl,ls1028a-plldig"},

Nitpick: Add a space before }

> +       { }
> +};
> +MODULE_DEVICE_TABLE(of, plldig_clk_id);
> +