From mboxrd@z Thu Jan 1 00:00:00 1970 From: maxime.ripard@free-electrons.com (Maxime Ripard) Date: Tue, 19 May 2015 22:53:43 +0200 Subject: [PATCH 3/8] clk: sunxi: Add a driver for the PLL2 In-Reply-To: References: <1430565879-28113-1-git-send-email-maxime.ripard@free-electrons.com> <1430565879-28113-4-git-send-email-maxime.ripard@free-electrons.com> <20150515074520.GR4004@lukather> <20150515144439.GZ4004@lukather> Message-ID: <20150519205343.GZ4004@lukather> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, May 19, 2015 at 03:58:09PM +0800, Chen-Yu Tsai wrote: > >> >> > +#define SUN4I_PLL2_PRE_DIV_VALUE 4 > >> >> > + > >> >> > +#define SUN4I_PLL2_OUTPUTS 4 > >> >> > + > >> >> > +static void sun4i_a10_get_pll2_base_factors(u32 *freq, u32 parent_rate, > >> >> > + u8 *n, u8 *k, u8 *m, u8 *p) > >> >> > +{ > >> >> > + /* > >> >> > + * Normalize the frequency to a multiple of (24 MHz / Fixed > >> >> > + * PRE-DIV) > >> >> > + */ > >> >> > + *freq = round_down(*freq, parent_rate / SUN4I_PLL2_PRE_DIV_VALUE); > >> >> > + > >> >> > + /* We were called to round the frequency, we can return */ > >> >> > + if (!n) > >> >> > + return; > >> >> > + > >> >> > + *n = *freq * SUN4I_PLL2_PRE_DIV_VALUE / parent_rate; > >> >> > + > >> >> > + /* > >> >> > + * Even though the pre-divider can be changed, we don't really > >> >> > + * care and we can just fix it to 4. > >> >> > + */ > >> >> > + *m = SUN4I_PLL2_PRE_DIV_VALUE; > >> >> > +} > >> >> > + > >> >> > +static struct clk_factors_config sun4i_a10_pll2_base_config = { > >> >> > + .mshift = SUN4I_PLL2_PRE_DIV, > >> >> > + .mwidth = 5, > >> >> > + .nshift = SUN4I_PLL2_N, > >> >> > + .nwidth = 7, > >> >> > + > >> >> > + .m_zero = 1, > >> >> > + .n_zero = 1, > >> >> > +}; > >> >> > + > >> >> > +static const struct factors_data sun4i_a10_pll2_base_data __initconst = { > >> >> > + .enable = SUN4I_PLL2_ENABLE, > >> >> > + .table = &sun4i_a10_pll2_base_config, > >> >> > + .getter = sun4i_a10_get_pll2_base_factors, > >> >> > + .name = "pll2-base", > >> >> > +}; > >> >> > + > >> >> > +static DEFINE_SPINLOCK(sun4i_a10_pll2_lock); > >> >> > + > >> >> > +static void __init sun4i_pll2_setup(struct device_node *node) > >> >> > +{ > >> >> > + const char *clk_name = node->name, *parent; > >> >> > + struct clk_onecell_data *clk_data; > >> >> > + struct clk **clks, *base_clk; > >> >> > + void __iomem *reg; > >> >> > + u32 val; > >> >> > + > >> >> > + reg = of_io_request_and_map(node, 0, of_node_full_name(node)); > >> >> > + if (IS_ERR(reg)) > >> >> > + return; > >> >> > + > >> >> > + clk_data = kzalloc(sizeof(*clk_data), GFP_KERNEL); > >> >> > + if (!clk_data) > >> >> > + goto err_unmap; > >> >> > + > >> >> > + clks = kcalloc(SUN4I_PLL2_OUTPUTS, sizeof(struct clk *), GFP_KERNEL); > >> >> > + if (!clks) > >> >> > + goto err_free_data; > >> >> > + > >> >> > + base_clk = sunxi_factors_register(node, &sun4i_a10_pll2_base_data, > >> >> > + &sun4i_a10_pll2_lock, reg); > >> >> > >> >> Why aren't you using divs_clk for this? It seems right for the job. > >> > > >> > As far as I know, divs_clk can only handle a single divider, and not > >> > two subsequent dividers like this one uses. > >> > >> I thought we were setting the post divider to 4 so the outputs match > >> the names? Maybe we could get it in as is (with the above comment > >> addressed), and refactor it later. I'm still stuck on factors_clk > >> stuff.... > > > > We are, but the pre-div is considered as the M factor, and the N > > factor as N, so we can't really consider it as a single divider. > > Isn't pre-div used by all the clocks? > > The manual lists: > > 1X = 48*N / pre-div / post-div / 2 > 2X = 48*N / pre-div / 4 > 4X = 48*N / pre-div / 2 > 8X = 48*N / pre-div > > So couldn't you have a base factor clock as 24*N / pre-div, > and the outputs as follows? > > 1X = base / post-div > 2X = base / 2 > 4X = base > 8X = base * 2 Good thing that it's what was done in this patch then :) > > Thinking a bit more about this, what we could do though, is splitting > > the pll2-base clock in half, one that would expose a single divider > > using clk-divider for the pre-divider, then a factor clock for the N > > factor, and then multiple dividers for the post-divider and other > > outputs. > > > > I wonder if that could not even be made that way for all the factors > > clock. That would reduce the needed logic in the drivers a lot. > > Taking apart what should be an integrated clock into separate parts > kind of makes the clock tree ugly. :( But it would remove the amount of code that we maintain, extend and debug by our own in favor of common, well-tested and factored code. Maxime -- Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 819 bytes Desc: Digital signature URL: