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

[Michael Walle <michael@walle.cc>]

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.

+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 ;)

>> +       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.

-michael