linux-kernel - Re: [PATCH 01/08] mach-shmobile: Emma Mobile EV2 SoC base support V3

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Date:	Wed, 16 May 2012 18:49:05 +0900
From:	Magnus Damm <magnus.damm@...il.com>
To:	Paul Mundt <lethal@...ux-sh.org>
Cc:	linux-arm-kernel@...ts.infradead.org, linux@....linux.org.uk,
	arnd@...db.de, linux-sh@...r.kernel.org,
	linux-kernel@...r.kernel.org, rjw@...k.pl, horms@...ge.net.au,
	olof@...om.net
Subject: Re: [PATCH 01/08] mach-shmobile: Emma Mobile EV2 SoC base support V3

On Wed, May 16, 2012 at 3:56 PM, Paul Mundt <lethal@...ux-sh.org> wrote:
> On Wed, May 16, 2012 at 03:44:58PM +0900, Magnus Damm wrote:
>> +static int emev2_gclk_enable(struct clk *clk)
>> +{
>> +     iowrite32(ioread32(clk->mapped_reg) | (1 << clk->enable_bit),
>> +               clk->mapped_reg);
>> +     return 0;
>> +}
>> +
>> +static void emev2_gclk_disable(struct clk *clk)
>> +{
>> +     iowrite32(ioread32(clk->mapped_reg) & ~(1 << clk->enable_bit),
>> +               clk->mapped_reg);
>> +}
>> +
>> +static struct sh_clk_ops emev2_gclk_clk_ops = {
>> +     .enable         = emev2_gclk_enable,
>> +     .disable        = emev2_gclk_disable,
>> +     .recalc         = followparent_recalc,
>> +};
>> +
>> +static int __init emev2_gclk_register(struct clk *clks, int nr)
>> +{
>> +     struct clk *clkp;
>> +     int ret = 0;
>> +     int k;
>> +
>> +     for (k = 0; !ret && (k < nr); k++) {
>> +             clkp = clks + k;
>> +             clkp->ops = &emev2_gclk_clk_ops;
>> +             ret |= clk_register(clkp);
>> +     }
>> +
>> +     return ret;
>> +}
>> +
> This all looks like a pointless abstraction. This is basically a verbatim
> copy of the sh_clk_mstp32 routines.

At a first glance maybe, but the operation is inverted compared to MSTP32.

So, at disable time gclk clears the bit. MSTP32 sets the bit.

> I suppose this is a case where you want to use the mstp32 routines but
> don't specifically have div4/div6 clocks to manage so you aren't setting
> SH_CLK_CPG. Perhaps we should just move the sh_clk_mstp32 stuff out so
> it's provided regardless of the CPG setting and rename it to drop the
> mstp32 connotations. It's really only the div4/div6 stuff that has any
> CPG-specific behaviour at this point anyways.

Perhaps we could base this code on MSTP32 and CPG, but I believe it is
better just to move to common clocks directly. So in this case for
gclk we can instead use code in drivers/clk/clk-gate.c.

Cheers,

/ magnus
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