From mboxrd@z Thu Jan 1 00:00:00 1970 From: maxime.ripard@free-electrons.com (Maxime Ripard) Date: Tue, 29 Mar 2016 11:38:27 +0200 Subject: [PATCH] clk: sunxi: Accept a greater rate when setting a parent clock In-Reply-To: <20160321092549.4e6245e4f02839e29aeb86a9@free.fr> References: <20160310081658.B749246B@mail.free-electrons.com> <20160321072546.GT30977@lukather> <20160321092549.4e6245e4f02839e29aeb86a9@free.fr> Message-ID: <20160329093827.GH30977@lukather> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi, On Mon, Mar 21, 2016 at 09:25:49AM +0100, Jean-Francois Moine wrote: > On Mon, 21 Mar 2016 08:25:46 +0100 > Maxime Ripard wrote: > > > > - /* find the parent that can help provide the fastest rate <= rate */ > > > + /* find the parent that can help provide the fastest rate */ > > > num_parents = clk_hw_get_num_parents(hw); > > > for (i = 0; i < num_parents; i++) { > > > parent = clk_hw_get_parent_by_index(hw, i); > > > @@ -100,7 +100,7 @@ static int clk_factors_determine_rate(struct clk_hw *hw, > > > child_rate = clk_factors_round_rate(hw, req->rate, > > > &parent_rate); > > > > > > - if (child_rate <= req->rate && child_rate > best_child_rate) { > > > + if (child_rate > best_child_rate) { > > > > I'm not sure this would work, since you'll end up picking the fastest > > rate without considering whether it is the closest or not. > > > > I guess what you want here is using the absolute difference between > > the requested rate and the rate you're evaluating. > > > > That being said, we had a similar discussion for SPI around a month > > ago where we wanted a rate strictly lower than the requested one. I > > guess it's time to add a flag to tell how you want to round. > > You are right, I just removed half of the constraint, but I still wonder > why does this sequence introduced by the commit 862b728387aef3a37 > (clk: sunxi: factors: automatic reparenting support) do > "provide the fastest rate <= rate" > instead of > "provide the closest rate" ? I guess it's a confusing wording, in this case where you try to have the closest rate but below the requested rate, what you want is actually the fastest rate that doesn't trip above the requested rate, hence the comment I guess. 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: