linux-kernel - Re: [PATCH] clk: imx: gate2: Fix the is

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Message-ID: <20201028101552.GA26805@pengutronix.de>
Date:   Wed, 28 Oct 2020 11:15:52 +0100
From:   Sascha Hauer <s.hauer@...gutronix.de>
To:     Abel Vesa <abel.vesa@....com>
Cc:     Mike Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <kernel@...gutronix.de>,
        Fabio Estevam <fabio.estevam@....com>,
        Anson Huang <anson.huang@....com>,
        Jacky Bai <ping.bai@....com>, Peng Fan <peng.fan@....com>,
        Dong Aisheng <aisheng.dong@....com>, linux-clk@...r.kernel.org,
        NXP Linux Team <linux-imx@....com>,
        linux-arm-kernel@...ts.infradead.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] clk: imx: gate2: Fix the is_enabled op

On Wed, Oct 28, 2020 at 11:50:57AM +0200, Abel Vesa wrote:
> On 20-10-28 09:24:12, Sascha Hauer wrote:
> > Hi Abel,
> > 
> > On Mon, Oct 26, 2020 at 08:50:48PM +0200, Abel Vesa wrote:
> > > The clock is considered to be enabled only if the controlling bits
> > > match the cgr_val mask. Also make sure the is_enabled returns the
> > > correct vaule by locking the access to the register.
> > > 
> > > Signed-off-by: Abel Vesa <abel.vesa@....com>
> > > Fixes: 1e54afe9fcfe ("clk: imx: gate2: Allow single bit gating clock")
> > > ---
> > >  drivers/clk/imx/clk-gate2.c | 60 ++++++++++++++++++++-------------------------
> > >  drivers/clk/imx/clk.h       |  8 ++----
> > >  2 files changed, 29 insertions(+), 39 deletions(-)
> > > 
> > > diff --git a/drivers/clk/imx/clk-gate2.c b/drivers/clk/imx/clk-gate2.c
> > > index 7eed708..f320bd2b 100644
> > > --- a/drivers/clk/imx/clk-gate2.c
> > > +++ b/drivers/clk/imx/clk-gate2.c
> > > @@ -37,10 +37,22 @@ struct clk_gate2 {
> > >  
> > >  #define to_clk_gate2(_hw) container_of(_hw, struct clk_gate2, hw)
> > >  
> > > +static void clk_gate2_do_shared_clks(struct clk_hw *hw, bool enable)
> > > +{
> > > +	struct clk_gate2 *gate = to_clk_gate2(hw);
> > > +	u32 reg;
> > > +
> > > +	reg = readl(gate->reg);
> > > +	if (enable)
> > > +		reg |= gate->cgr_val << gate->bit_idx;
> > > +	else
> > > +		reg &= ~(gate->cgr_val << gate->bit_idx);
> > 
> > Shouldn't this be:
> > 
> > 	reg &= ~(3 << gate->bit_idx);
> > 	if (enable)
> > 		reg |= gate->cgr_val << gate->bit_idx;
> > 
> > At least that's how it was without this patch and that's how it makes
> > sense to me with cgr_val != 3.
> > 
> 
> Well, that's the actual problem. The value 3 forces all the clocks
> that register with this clock type to have 2 bits for controlling the gate.
> 
> My patch (though now I think I should split it into 2 separate patches) allows
> two HW gates to be controlled by as many bits necessary. For example, there
> could be multiple HW gates that are controled by the same bit. By passing
> the cgr_val when registering the clocks you can specify how many bits (as a mask)
> control all those HW gates that share their control bits.

cgr_val is not a mask, it's a value that shall be written to the two
bits to enable the clock. cgr_val could also be 0b10, see imx_clk_gate2_cgr().

Sascha

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