Re: [PATCH] clk: Add axi-clkgen driver

Lars-Peter Clausen
2013-01-23T10:00:41Z

On 01/22/2013 06:55 PM, Mike Turquette wrote:
> Quoting Lars-Peter Clausen (2013-01-09 10:12:00)
> <snip>
>> +static void axi_clkgen_write(struct axi_clkgen *axi_clkgen,
>> + unsigned int reg, unsigned int val)
>> +{
>> + iowrite32(val, axi_clkgen->base + reg);
>
> Silly question: any reason to use this over readl()? This is more for
> my understanding than a real criticism.

I think I read somewhere at some point that ioread{8,16,32} is preferred
over write{b,h,l} in new code.

>
>> +}
>> +
>> +static void axi_clkgen_read(struct axi_clkgen *axi_clkgen,
>> + unsigned int reg, unsigned int *val)
>> +{
>> + *val = ioread32(axi_clkgen->base + reg);
>
> Same as above, any reason to use this over writel?

Same answer.

>
> <snip>
>> +static unsigned long axi_clkgen_recalc_rate(struct clk_hw *clk_hw,
>> + unsigned long parent_rate)
>> +{
>> + struct axi_clkgen *axi_clkgen = clk_hw_to_axi_clkgen(clk_hw);
>> + unsigned int d, m, dout;
>> + unsigned int reg;
>> +
>> + axi_clkgen_read(axi_clkgen, AXI_CLKGEN_REG_CLK_OUT1, &reg);
>> + dout = (reg & 0x3f) + ((reg >> 6) & 0x3f);
>> + axi_clkgen_read(axi_clkgen, AXI_CLKGEN_REG_CLK_DIV, &reg);
>> + d = (reg & 0x3f) + ((reg >> 6) & 0x3f);
>> + axi_clkgen_read(axi_clkgen, AXI_CLKGEN_REG_CLK_FB1, &reg);
>> + m = (reg & 0x3f) + ((reg >> 6) & 0x3f);
>> +
>> + if (d == 0 || dout == 0)
>> + return 0;
>> +
>> + return parent_rate / d * m / dout;
>
> Any chance of overflow here? Maybe do_div should be used?

Not if all the parameters are within spec. But since this is on a slowpath I
guess it does not hurt to use do_div.

Will send a v2.

Thanks for the review,
- Lars