From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Turquette Subject: Re: [PATCH v3] clk_mux: Fix set_parent doing the wrong thing when INDEX_BIT && index >= 3 Date: Wed, 19 Nov 2014 14:04:49 -0800 Message-ID: <20141119220449.25314.56163@quantum> References: <1416404939-609-1-git-send-email-hdegoede@redhat.com> Reply-To: linux-sunxi-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: In-Reply-To: <1416404939-609-1-git-send-email-hdegoede-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> List-Post: , List-Help: , List-Archive: , List-Unsubscribe: , Cc: Philipp Zabel , Grant Likely , Tero Kristo , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, devicetree , linux-sunxi-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org, Hans de Goede List-Id: devicetree@vger.kernel.org Quoting Hans de Goede (2014-11-19 05:48:59) > If CLK_MUX_INDEX_BIT is set, then each bit turns on / off a single parent, > so theoretically multiple parents could be enabled at the same time, but in > practice only one bit should ever be 1. So to select parent 0, set > the register (*) to 0x01, to select parent 1 set it 0x02, parent 2, 0x04, > parent 3, 0x08, etc. > > But the current code does: > > if (mux->flags & CLK_MUX_INDEX_BIT) > index = (1 << ffs(index)); > > Which means that: > > For an input index of 0, ffs returns 0, so we set the register > to 0x01, ok. > > For an input index of 1, ffs returns 1, so we set the register > to 0x02, ok. > > For an input index of 2, ffs returns 2, so we set the register > to 0x04, ok. > > For an input index of 3, ffs returns 1, so we set the register > to 0x02, not good! > > The code should simply be: > > if (mux->flags & CLK_MUX_INDEX_BIT) > index = 1 << index; > > Which always does the right thing, this commit fixes this. > > Signed-off-by: Hans de Goede Applied to clk-next towards 3.19. I don't think any merged platforms are hitting this bug in the field so I've not put it into -fixes. Thanks, Mike > --- > drivers/clk/clk-mux.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/clk/clk-mux.c b/drivers/clk/clk-mux.c > index 4f96ff3..6e1ecf9 100644 > --- a/drivers/clk/clk-mux.c > +++ b/drivers/clk/clk-mux.c > @@ -77,7 +77,7 @@ static int clk_mux_set_parent(struct clk_hw *hw, u8 index) > > else { > if (mux->flags & CLK_MUX_INDEX_BIT) > - index = (1 << ffs(index)); > + index = 1 << index; > > if (mux->flags & CLK_MUX_INDEX_ONE) > index++; > -- > 2.1.0 >