Re: [PATCH 4/5] BCM2835: add support (arch)

[Sascha Hauer <s.hauer@pengutronix.de>]

On Thu, Oct 18, 2012 at 12:27:14AM +0200, Carlo Caione wrote:
> 
> On Oct 16, 2012, at 11:24 PM, Sascha Hauer <s.hauer@pengutronix.de> wrote:
> 
> > On Tue, Oct 16, 2012 at 08:04:44PM +0200, Carlo Caione wrote:
> >> +
> >> +static struct clk ref_3_clk = {
> >> +	.rate = 3 * 1000 * 1000,
> >> +};
> >> +
> >> +static struct clk ref_1_clk = {
> >> +	.rate = 1 * 1000 * 1000,
> >> +};
> > 
> > Add a 'select COMMON_CLK' to your Kconfig and do a:
> > 
> > 	clk_dummy = clk_fixed("dummy", 0);
> > 	clk_ref_3 = clk_fixed("ref3", 3 * 1000 * 1000);
> > 	clk_ref_1 = clk_fixed("ref1", 1 * 1000 * 1000);
> > 
> > Then you can drop your clk code and get a clk_dump command
> > which you can use to see what clocks you have.
> 
> RFC
> 
> ok I ask here before submitting the whole set because I'm not sure if this is a convenient solution.
> I'm not sure if you are suggesting to have two different clock definition one for clk_fixed and the other one for clkdev,
> so I was thinking something like:
> 
> enum brcm_clks {
> 	dummy, clk_ref_3, clk_ref_1, clks_max
> };
> 
> static struct clk *clks[clks_max];
> 
> int brmc_clk_create(struct clk *clk, const char *con_id, const char *dev_id)
> {
> 	struct clk_lookup *clkdev;
> 
> 	clkdev = clkdev_alloc(clk, con_id, dev_id);
> 	if (!clkdev)
> 		return -ENOMEM;
> 	clkdev_add(clkdev);
> 	return 0;
> }
> 
> static int bcm2835_clk_init(void)
> {
> 	int ret; 
> 
> 	clks[dummy] = clk_fixed("dummy", 0);
> 	ret = brmc_clk_create(clks[dummy], "apb_pclk", NULL);
> 	if (ret)
> 		goto clk_err;
> 
> 	clks[clk_ref_3] = clk_fixed("ref3", 3 * 1000 * 1000);
> 	ret = brmc_clk_create(clks[clk_ref_3], NULL, "uart0-pl0110");
> 	if (ret)
> 		goto clk_err;
> 
> 	clks[clk_ref_1] = clk_fixed("ref1", 1 * 1000 * 1000);
> 	ret = brmc_clk_create(clks[clk_ref_1], NULL, "bcm2835-cs");
> 	if (ret)
> 		goto clk_err;

The above is basically what I was thinking of. The only thing I see that
this *looks* like there is exactly one lookup per clock. This indeed is
the case currenty here, but this does not have to be true. A clock may
have multiple lookups, for example the ref3 clk may also be used by the
lcd controller or something else. So I suggest to first register all
clocks and the lookups afterwards.

What you have as brmc_clk_create could well be a generic helper
function, it will be useful for others aswell.

BTW error checking here is a good idea, but a rollback of the allocated
resources will be unnecessary as you are doomed anyway when something
fails here.

Sascha


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