Hi Andy, On 17 July 2018 15:19, Andy Shevchenko wrote: > On Tue, 2018-07-17 at 12:42 +0000, Phil Edworthy wrote: > > > > While your point sounds valid (don't remember how clk_get() is > > > implemented), NULL is also OK to have. > > > > Ok as in there is no bus clock, right? > > So it should be: > > if (!IS_ERR_OR_NULL (dev->busclk)) > > Nope, NULL is no error case for optional clock. I must be missing something here... I agree that NULL for an optional clock is not an error. However, the code above is now: + if (prepare) { + /* Optional bus clock */ + if (!IS_ERR_OR_NULL(dev->busclk)) { + ret = clk_prepare_enable(dev->busclk); + if (ret) + return ret; + } + return clk_prepare_enable(dev->clk); + } So, if you have a valid busclk, it gets enabled, otherwise it is left alone. Thanks Phil