[U-Boot] [PATCH v2 04/28] armv8/ls2085a: Fix generic timer clock source

[York Sun]

On 03/20/2015 10:34 AM, Mark Rutland wrote:
> Hi,
> 
> On Thu, Mar 19, 2015 at 08:34:22PM +0000, York Sun wrote:
>> The timer clock is system clock divided by 4, not fixed 12MHz. This is
>> common to the SoC, not board specific.
>>
>> Signed-off-by: York Sun <yorksun at freescale.com>
>>
>> ---
>>
>> Changes in v2:
>>   Fix CNTFRQ for secondary cores when COUNTER_FREQUENCY_REAL is defined.
>>
>>  README                                  |    8 ++++++++
>>  arch/arm/cpu/armv8/fsl-lsch3/cpu.c      |   26 ++++++++++++++++++++++++++
>>  arch/arm/cpu/armv8/fsl-lsch3/lowlevel.S |    6 ++++++
>>  arch/arm/cpu/armv8/fsl-lsch3/mp.h       |    1 +
>>  board/freescale/ls2085a/ls2085a.c       |   18 ------------------
>>  include/configs/ls2085a_common.h        |    6 +++++-
>>  6 files changed, 46 insertions(+), 19 deletions(-)
>>
>> diff --git a/README b/README
>> index f473515..776ebf4 100644
>> --- a/README
>> +++ b/README
>> @@ -690,6 +690,14 @@ The following options need to be configured:
>>  		exists, unlike the similar options in the Linux kernel. Do not
>>  		set these options unless they apply!
>>  
>> +		COUNTER_FREQUENCY
>> +		Generic timer clock source frequency.
>> +
>> +		COUNTER_FREQUENCY_REAL
>> +		Generic timer clock source frequency if the real clock is
>> +		different from COUNTER_FREQUENCY, and can only be determined
>> +		at run time.
>> +
>>  		NOTE: The following can be machine specific errata. These
>>  		do have ability to provide rudimentary version and machine
>>  		specific checks, but expect no product checks.
>> diff --git a/arch/arm/cpu/armv8/fsl-lsch3/cpu.c b/arch/arm/cpu/armv8/fsl-lsch3/cpu.c
>> index 94fd147..f75b21d 100644
>> --- a/arch/arm/cpu/armv8/fsl-lsch3/cpu.c
>> +++ b/arch/arm/cpu/armv8/fsl-lsch3/cpu.c
>> @@ -395,3 +395,29 @@ int arch_early_init_r(void)
>>  
>>  	return 0;
>>  }
>> +
>> +int timer_init(void)
>> +{
>> +	u32 __iomem *cntcr = (u32 *)CONFIG_SYS_FSL_TIMER_ADDR;
>> +	u32 __iomem *cltbenr = (u32 *)CONFIG_SYS_FSL_PMU_CLTBENR;
>> +#ifdef COUNTER_FREQUENCY_REAL
>> +	unsigned long cntfrq = COUNTER_FREQUENCY_REAL;
>> +
>> +	/* Update with accurate clock frequency */
>> +	asm volatile("msr cntfrq_el0, %0" : : "r" (cntfrq) : "memory");
> 
> The commit message says that this can only be determined at runtime, but
> this looks like we're writing a compile-time static value.
> 

The macro COUNTER_FREQUENCY_REA is (CONFIG_SYS_CLK_FREQ/4), where
CONFIG_SYS_CLK_FREQ is a function call get_board_sys_clk().

>> +
>> +	__real_cntfrq = cntfrq;	/* update for secondary cores */
> 
> Do we need anything in the way or barriers and/or cache flushing to
> ensure that this is visible to the secondary CPUs? Or is the MMU off at
> this point?

It is flushed before booting secondary cores. But I am relying on the trick of
enabling cache on flash. It may not be as reliable if someone decide to disable
the cache to begin with. I will move the code to somewhere safe in next version.

> 
>> +#endif
>> +
>> +	/* Enable timebase for all clusters.
>> +	 * It is safe to do so even some clusters are not enabled.
>> +	 */
>> +	out_le32(cltbenr, 0xf);
>> +
>> +	/* Enable clock for timer
>> +	 * This is a global setting.
>> +	 */
>> +	out_le32(cntcr, 0x1);
>> +
>> +	return 0;
>> +}
>> diff --git a/arch/arm/cpu/armv8/fsl-lsch3/lowlevel.S b/arch/arm/cpu/armv8/fsl-lsch3/lowlevel.S
>> index 886576e..8d330ff 100644
>> --- a/arch/arm/cpu/armv8/fsl-lsch3/lowlevel.S
>> +++ b/arch/arm/cpu/armv8/fsl-lsch3/lowlevel.S
>> @@ -224,6 +224,9 @@ ENTRY(secondary_boot_func)
>>  	/* physical address of this cpus spin table element */
>>  	add	x11, x1, x0
>>  
>> +	ldr	x0, =__real_cntfrq
>> +	ldr	x0, [x0]
>> +	msr	cntfrq_el0, x0	/* set with real frequency */
>>  	str	x9, [x11, #16]	/* LPID */
>>  	mov	x4, #1
>>  	str	x4, [x11, #8]	/* STATUS */
>> @@ -275,6 +278,9 @@ ENDPROC(secondary_switch_to_el1)
>>  
>>  	/* 64 bit alignment for elements accessed as data */
>>  	.align 4
>> +	.global __real_cntfrq
>> +__real_cntfrq:
>> +	.quad 0x17d7840		/* 25MHz */
> 
> I think this would be better as COUNTER_FREQUENCY, so as to avoid
> duplicating the value.

Good idea. Will fix in next version.

York