On 02/20/2013 06:26 AM, Laxman Dewangan wrote: > On Wednesday 20 February 2013 06:41 PM, Mark Brown wrote: >> * PGP Signed by an unknown key >> >> On Wed, Feb 20, 2013 at 05:59:03PM +0530, Laxman Dewangan wrote: >>>>> + tspi->clk = devm_clk_get(&pdev->dev, "spi"); >>>> Does this HW block use multiple clocks? If not, I think s/"spi"/NULL/ >>>> there, just like the Tegra20 driver. >>> No, spi controller uses the only one clock. I will change to NULL. >> I'm never convinced that NULL is a helpful clock name to pick, it's not >> awesome if you ever acquire a second clock. > > I had other idea of okeeping clock name here for power optimization. > Spi controller can take the power source ffrom different clock source > say clk_m (crystal) and pllp. > > I want to set the parent clock dynamically based on required speed so > that if the desire speed can be meet from clk_m, no need to increase pll > count and possible we may endup with siwtchng off pllp which can save > power. > > So for this I may require > > spi_clk = devm_clk_get(&pdev->dev, "spi"); > spi_clkm = devm_clk_get(&pdev->dev, "clmkm"); > spi_pllp = devm_clk_get(&pdev->dev, "pllp"); > > and call clk_set_parent(spi_clk, spi_clkm) or clk_set_parent(spi_clk, > spi_pllp). OK, so that's certainly an argument for requesting a specific clock name rather than NULL. But, please do think this approach through fully. The DT binding needs to define which clock-names the driver requires to be present, and any optional clock names. DT bindings are supposed to be immutable, or perhaps extendible in a completely backwards-compatible fashion. This implies that you need to have thought through the entire list of clocks that the driver might want in the DT clock-names property when you first write the DT binding documentation... -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
