RE: [EXT] Re: [v3 2/2] clk: ls1028a: Add clock driver for Display output interface

[Wen He]

> -----Original Message-----
> From: Stephen Boyd <sboyd@xxxxxxxxxx>
> Sent: 2019å8æ23æ 9:27
> To: Mark Rutland <mark.rutland@xxxxxxx>; Michael Turquette
> <mturquette@xxxxxxxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx>; Wen He
> <wen.he_1@xxxxxxx>; devicetree@xxxxxxxxxxxxxxx; linux-clk@xxxxxxxxxxxxxxx;
> linux-devel@xxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Cc: Leo Li <leoyang.li@xxxxxxx>; liviu.dudau@xxxxxxx; Wen He
> <wen.he_1@xxxxxxx>
> Subject: [EXT] Re: [v3 2/2] clk: ls1028a: Add clock driver for Display output
> interface
> 
> Caution: EXT Email
> 
> Quoting Wen He (2019-08-21 19:08:47)
> > 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@xxxxxxx>
> > ---
> > change in v3:
> >         - remove the OF dependency
> >         - use clk_parent_data instead of parent_name
> >
> >  drivers/clk/Kconfig      |  10 ++
> >  drivers/clk/Makefile     |   1 +
> >  drivers/clk/clk-plldig.c | 283
> > +++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 294 insertions(+)
> >  create mode 100644 drivers/clk/clk-plldig.c
> >
> > diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig index
> > 801fa1cd0321..ab05f342af04 100644
> > --- a/drivers/clk/Kconfig
> > +++ b/drivers/clk/Kconfig
> > @@ -223,6 +223,16 @@ config CLK_QORIQ
> >           This adds the clock driver support for Freescale QorIQ platforms
> >           using common clock framework.
> >
> > +config CLK_LS1028A_PLLDIG
> > +        bool "Clock driver for LS1028A Display output"
> > +        depends on ARCH_LAYERSCAPE || COMPILE_TEST
> > +        default ARCH_LAYERSCAPE
> > +        help
> > +          This driver support the Display output interfaces(LCD, DPHY)
> pixel clocks
> > +          of the QorIQ Layerscape LS1028A, as implemented TSMC
> CLN28HPM PLL. Not all
> > +          features of the PLL are currently supported by the driver. By
> default,
> > +          configured bypass mode with this PLL.
> > +
> >  config COMMON_CLK_XGENE
> >         bool "Clock driver for APM XGene SoC"
> >         default ARCH_XGENE
> > diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile index
> > 0cad76021297..c8e22a764c4d 100644
> > --- a/drivers/clk/Makefile
> > +++ b/drivers/clk/Makefile
> > @@ -44,6 +44,7 @@ obj-$(CONFIG_COMMON_CLK_OXNAS)
> += clk-oxnas.o
> >  obj-$(CONFIG_COMMON_CLK_PALMAS)                += clk-palmas.o
> >  obj-$(CONFIG_COMMON_CLK_PWM)           += clk-pwm.o
> >  obj-$(CONFIG_CLK_QORIQ)                        += clk-qoriq.o
> > +obj-$(CONFIG_CLK_LS1028A_PLLDIG)       += clk-plldig.o
> >  obj-$(CONFIG_COMMON_CLK_RK808)         += clk-rk808.o
> >  obj-$(CONFIG_COMMON_CLK_HI655X)                += clk-hi655x.o
> >  obj-$(CONFIG_COMMON_CLK_S2MPS11)       += clk-s2mps11.o
> > diff --git a/drivers/clk/clk-plldig.c b/drivers/clk/clk-plldig.c new
> > file mode 100644 index 000000000000..c5ce80a46fd4
> > --- /dev/null
> > +++ b/drivers/clk/clk-plldig.c
> > @@ -0,0 +1,283 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +// Copyright 2019 NXP
> 
> Please leave this as C style /* */ comment for the NXP part, but comply with
> the SPDX comment style of // on the first line.
> 
> > +
> > +static long plldig_round_rate(struct clk_hw *hw, unsigned long rate,
> > +               unsigned long *parent) {
> > +       unsigned long parent_rate = *parent;
> > +       unsigned long round_rate;
> > +       u32 mult = 0, rfdphi1 = 0;
> > +       bool found = false;
> > +
> > +       found = plldig_is_valid_range(rate, parent_rate, &mult,
> > +                                       &rfdphi1, &round_rate);
> > +       if (!found) {
> > +               pr_warn("%s: unable to round rate %lu, parent
> rate :%lu\n",
> > +                               clk_hw_get_name(hw), rate,
> parent_rate);
> > +               return 0;
> 
> This can return an error instead? In fact, you may want to use determine_rate
> clk op instead.
> 
> > +       }
> > +
> > +       return round_rate / rfdphi1;
> > +}
> > +
> > +static int plldig_set_rate(struct clk_hw *hw, unsigned long rate,
> > +               unsigned long parent_rate) {
> > +       struct clk_plldig *data = to_clk_plldig(hw);
> > +       bool valid = false;
> > +       unsigned long round_rate = 0;
> > +       u32 rfdphi1 = 0, val, mult = 0, cond = 0;
> > +       int ret = -ETIMEDOUT;
> > +
> > +       valid = plldig_is_valid_range(rate, parent_rate, &mult,
> > +                                       &rfdphi1, &round_rate);
> > +       if (!valid) {
> > +               pr_warn("%s: unable to support rate %lu,
> parent_rate: %lu\n",
> > +                               clk_hw_get_name(hw), rate,
> > + parent_rate);
> 
> Shouldn't determine_rate or round_rate make this impossible to hit in practice?
> I mean that those ops should prevent the rate from being rounded to such a
> frequency that it becomes invalid.
> 
> > +               return -EINVAL;
> > +       }
> > +
> > +       val = readl(data->regs + PLLDIG_REG_PLLDV);
> > +       val = mult;
> > +       rfdphi1 = PLLDIG_SET_RFDPHI1(rfdphi1);
> > +       val |= rfdphi1;
> > +
> > +       writel(val, data->regs + PLLDIG_REG_PLLDV);
> > +
> > +       /* delay 200us make sure that old lock state is cleared */
> > +       udelay(200);
> > +
> > +       /* Wait until PLL is locked or timeout (maximum 1000 usecs) */
> > +       ret = readl_poll_timeout_atomic(data->regs + PLLDIG_REG_PLLSR,
> cond,
> > +                                       cond & PLLDIG_LOCK_MASK,
> 0,
> > +                                       USEC_PER_MSEC);
> > +
> > +       return ret;
> > +}
> > +
> > +static const struct clk_ops plldig_clk_ops = {
> > +       .enable = plldig_enable,
> > +       .disable = plldig_disable,
> > +       .is_enabled = plldig_is_enabled,
> > +       .recalc_rate = plldig_recalc_rate,
> > +       .round_rate = plldig_round_rate,
> > +       .set_rate = plldig_set_rate,
> > +};
> [...]
> > +
> > +       ret = devm_clk_hw_register(dev, &data->hw);
> > +       if (ret) {
> > +               dev_err(dev, "failed to register %s clock\n", init.name);
> > +               return ret;
> > +       }
> > +
> > +       ret = devm_of_clk_add_hw_provider(dev, of_clk_hw_simple_get,
> &data->hw);
> > +       if (ret)
> > +               dev_err(dev, "failed adding the clock provider\n");
> > +
> > +       return ret;
> > +}
> > +
> > +static int plldig_clk_remove(struct platform_device *pdev) {
> > +       of_clk_del_provider(pdev->dev.of_node);
> 
> This isn't required. devm already does it.
> 
> > +       return 0;
> > +}
> > +
> > +static const struct of_device_id plldig_clk_id[] = {
> > +       { .compatible = "fsl,ls1028a-plldig", .data = NULL},
> 
> You can leave out the data assignment.

Thanks for the details review, will send next version.

Best Regards,
Wen