linux-kernel - Re: [PATCH] AT91: SAM9G45 - add a separate clock entry for every single TC block

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Date:	Wed, 08 Sep 2010 11:00:40 +0200
From:	Nicolas Ferre <nicolas.ferre@...el.com>
To:	"avictor.za@...il.com" <avictor.za@...il.com>,
	linux-arm-kernel@...ts.infradead.org
CC:	linux-kernel@...r.kernel.org, Fabian Godehardt <fg@...ix.com>
Subject: Re: [PATCH] AT91: SAM9G45 - add a separate clock entry for every
 single TC block

Le 07/09/2010 21:42, avictor.za@...il.com :
> hi,
> 
>> +/* One additional fake clock for second TC block */
>> +static struct clk tcb1_clk = {
>> +       .name           = "tcb1_clk",
>> +       .pmc_mask       = 0,
>> +       .type           = CLK_TYPE_PERIPHERAL,
>> +       .parent         = &tcb0_clk,
>> +};
>> +
> 
> Looking at this again...  since type is CLK_TYPE_PERIPHERAL, when you
> call clk_register() the "parent" is changed to the master clock.
> 
> Which means, then later you call clk_enable() the "pmc_mask" is still
> 0, so 0 gets written (in pmc_periph_mode) to AT91_PMC_PCER.  So the
> TCB clock won't be enabled.
> 
> Or am I missing something?

You are absolutely right!

What do you think about this modification of clk_register() function?

--- a/arch/arm/mach-at91/clock.c
+++ b/arch/arm/mach-at91/clock.c
@@ -501,7 +501,8 @@ postcore_initcall(at91_clk_debugfs_init);
 int __init clk_register(struct clk *clk)
 {
        if (clk_is_peripheral(clk)) {
-               clk->parent = &mck;
+               if (!clk->parent)
+                       clk->parent = &mck;
                clk->mode = pmc_periph_mode;
                list_add_tail(&clk->node, &clocks);
        }

It is a very little modification which implements what I had in mind
while creating a kind of "child peripheral" clock.

Best regards,
-- 
Nicolas Ferre

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