linux-kernel - Re: [PATCH v2 2/2] clk: fsl-sai: new driver

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Date:   Thu, 02 Jan 2020 00:09:28 -0800
From:   Stephen Boyd <sboyd@...nel.org>
To:     Michael Walle <michael@...le.cc>
Cc:     devicetree@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Michael Turquette <mturquette@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v2 2/2] clk: fsl-sai: new driver

Quoting Michael Walle (2020-01-01 07:15:32)
> 
> Hi Stephen,
> 
> thanks for the review.
> 
> Am 2019-12-24 09:05, schrieb Stephen Boyd:
> > Quoting Michael Walle (2019-12-09 15:33:05)
> >> diff --git a/drivers/clk/clk-fsl-sai.c b/drivers/clk/clk-fsl-sai.c
> >> new file mode 100644
> >> index 000000000000..b92054d15ab1
> >> --- /dev/null
> >> +++ b/drivers/clk/clk-fsl-sai.c
> >> @@ -0,0 +1,84 @@
> >> +// SPDX-License-Identifier: GPL-2.0
> >> +/*
> >> + * Freescale SAI BCLK as a generic clock driver
> >> + *
> >> + * Copyright 2019 Kontron Europe GmbH
> >> + */
> >> +
> >> +#include <linux/clk-provider.h>
> >> +#include <linux/err.h>
> >> +#include <linux/of.h>
> >> +#include <linux/of_address.h>
> >> +#include <linux/slab.h>
> >> +
> >> +#define I2S_CSR                0x00
> >> +#define I2S_CR2                0x08
> >> +#define CSR_BCE_BIT    28
> >> +#define CR2_BCD                BIT(24)
> >> +#define CR2_DIV_SHIFT  0
> >> +#define CR2_DIV_WIDTH  8
> >> +
> >> +struct fsl_sai_clk {
> >> +       struct clk_divider div;
> >> +       struct clk_gate gate;
> >> +       spinlock_t lock;
> >> +};
> >> +
> >> +static void __init fsl_sai_clk_setup(struct device_node *node)
> >> +{
> >> +       const char *clk_name = node->name;
> >> +       struct fsl_sai_clk *sai_clk;
> >> +       unsigned int num_parents;
> >> +       const char *parent_name;
> >> +       void __iomem *base;
> >> +       struct clk_hw *hw;
> >> +
> >> +       num_parents = of_clk_get_parent_count(node);
> >> +       if (!num_parents) {
> >> +               pr_err("%s: no parent found", clk_name);
> >> +               return;
> >> +       }
> >> +
> >> +       parent_name = of_clk_get_parent_name(node, 0);
> > 
> > Could this use the new way of specifying clk parents so that we don't
> > have to query DT for parent names and just let the core framework do it
> > whenever it needs to?
> 
> you mean specifying parent_data with .index = 0? Seems like 
> clk_composite
> does not support this. The parent can only be specified by supplying the
> clock names.
> 
> I could add that in a separate patch. What do you think about the
> following new functions, where a driver can use parent_data instead
> of parent_names.

I started doing this in
https://lkml.kernel.org/r/20190830150923.259497-1-sboyd@kernel.org but I
never got around to the composite clks. Sounds fine to add this new API
for your use case.

> 
> +struct clk *clk_register_composite_pdata(struct device *dev, const char 
> *name,
> +               const struct clk_parent_data *parent_data,
> +               struct clk_hw *mux_hw, const struct clk_ops *mux_ops,
> +               struct clk_hw *rate_hw, const struct clk_ops *rate_ops,
> +               struct clk_hw *gate_hw, const struct clk_ops *gate_ops,
> +               unsigned long flags);
> 
> +struct clk_hw *clk_hw_register_composite_pdata(struct device *dev,
> +               const char *name, const struct clk_parent_data 
> *parent_data,
> +               struct clk_hw *mux_hw, const struct clk_ops *mux_ops,
> +               struct clk_hw *rate_hw, const struct clk_ops *rate_ops,
> +               struct clk_hw *gate_hw, const struct clk_ops *gate_ops,
> +               unsigned long flags);
> 
> 
> >> +
> >> +       sai_clk = kzalloc(sizeof(*sai_clk), GFP_KERNEL);
> >> +       if (!sai_clk)
> >> +               return;
> >> +
> >> +       base = of_iomap(node, 0);
> >> +       if (base == NULL) {
> >> +               pr_err("%s: failed to map register space", clk_name);
> >> +               goto err;
> >> +       }
> >> +
> >> +       spin_lock_init(&sai_clk->lock);
> >> +
> >> +       sai_clk->gate.reg = base + I2S_CSR;
> >> +       sai_clk->gate.bit_idx = CSR_BCE_BIT;
> >> +       sai_clk->gate.lock = &sai_clk->lock;
> >> +
> >> +       sai_clk->div.reg = base + I2S_CR2;
> >> +       sai_clk->div.shift = CR2_DIV_SHIFT;
> >> +       sai_clk->div.width = CR2_DIV_WIDTH;
> >> +       sai_clk->div.lock = &sai_clk->lock;
> >> +
> >> +       /* set clock direction, we are the BCLK master */
> > 
> > Should this configuration come from DT somehow?
> 
> No, we are always master, because as a slave, there would be no clock
> output ;)

Got it.

> 
> >> +       writel(CR2_BCD, base + I2S_CR2);
> >> +
> >> +       hw = clk_hw_register_composite(NULL, clk_name, &parent_name, 
> >> 1,
> >> +                                      NULL, NULL,
> >> +                                      &sai_clk->div.hw, 
> >> &clk_divider_ops,
> >> +                                      &sai_clk->gate.hw, 
> >> &clk_gate_ops,
> >> +                                      CLK_SET_RATE_GATE);
> >> +       if (IS_ERR(hw))
> >> +               goto err;
> >> +
> >> +       of_clk_add_hw_provider(node, of_clk_hw_simple_get, hw);
> >> +
> >> +       return;
> >> +
> >> +err:
> >> +       kfree(sai_clk);
> >> +}
> >> +
> >> +CLK_OF_DECLARE(fsl_sai_clk, "fsl,vf610-sai-clock", 
> >> fsl_sai_clk_setup);
> > 
> > Is there a reason this can't be a platform device driver?
> 
> I don't think so, the user will be a sound codec for now. I'll convert 
> it
> to a platform device, in that case I could also use the devm_ variants.
> 

Awesome. Thanks!