Re: [PATCH] ARM: dts: Add missing CPU frequencies for Exynos5422/5800

[Markus Reichl <m.reichl@fivetechno.de>]

Hi Javier,

Am 16.12.2016 um 17:22 schrieb Javier Martinez Canillas:
> Hello Markus,
> 
> On 12/16/2016 06:08 AM, Markus Reichl wrote:
>> Am 16.12.2016 um 08:37 schrieb Krzysztof Kozlowski:
>>> On Thu, Dec 15, 2016 at 04:52:58PM -0800, Doug Anderson wrote:
>>>>> [ I added Arjun to Cc:, maybe he can help in explaining this issue
>>>>>   (unfortunately Inderpal's email is no longer working). ]
>>>>>
>>>>> Please also note that on Exynos5422/5800 SoCs the same ARM rail
>>>>> voltage is used for 1.9 GHz & 2.0 GHz OPPs as for the 1.8 GHz one.
>>>>> IOW if the problem exists it is already present in the mainline
>>>>> kernel.
>>>>
>>>> Interesting.  In the ChromeOS tree I see significantly higher voltages
>>>> needed...  Note that one might naively look at
>>>> <https://chromium.googlesource.com/chromiumos/third_party/kernel/+/chromeos-3.8/drivers/cpufreq/exynos5420-cpufreq.c#178>.
>>>>
>>>> 1362500, /* L0  2100 */
>>>> 1312500, /* L1  2000 */
>>>>
>>>> ..but, amazingly enough those voltages aren't used at all.  Surprise!
>>>>
>>>> I believe that the above numbers are actually not used and the ASV
>>>> numbers are used instead.  See
>>>> <https://chromium.googlesource.com/chromiumos/third_party/kernel/+/chromeos-3.8/arch/arm/mach-exynos/include/mach/asv-exynos542x.h#452>
>>>>
>>>> { 2100000,
>>>> 1350000, 1350000, 1350000, 1350000, 1350000,
>>>> 1337500, 1325000, 1312500, 1300000, 1287500,
>>>> 1275000, 1262500, 1250000, 1237500 },
>>>>
>>>> I believe that interpretation there is: some bins of the CPU can run
>>>> at 2.1 GHz just fine at 1.25 V but others need up to 1.35V.
>>>
>>> That is definitely the case. One could just look at vendors ASV table
>>> (for 1.9 GHz):
>>> { 1900000, 1300000, 1287500, 1262500, 1237500, 1225000, 1212500,
>>>                     1200000, 1187500, 1175000, 1162500, 1150000,
>>> 		             1137500, 1125000, 1112500, 1112500},
>>>
>>> The theoretical difference is up to 1.875V! From my experiments I saw
>>> BIN1 chips which should be the same... but some working on 1.2V, some on
>>> 1.225V (@1.9 GHz). I didn't see any requiring higher voltages but that
>>> does not mean that there aren't such...
>>>
>>>> ...so if you're running at 2.1 GHz at 1.25V then perhaps you're just
>>>> running on a CPU from a nice bin?
>>
>> I've been running the proposed frequency/voltage combinations without any
>> stability problems on my XU4, XU3 and even XU3-lite ( I did not delete the
>> nodes on XU3-lite dts) with make -j8 kernel and ssvb-cpuburn.
>> The chips are poorly cooled, especially the XU4 and quickly step down.
>>
>>>
>>> Would be nice to see a dump of PKG_ID and AUX_INFO chipid registers
>>> along with name of tested board. Because the "Tested on XU3" is not
>>> sufficient.
>>
>> If you point me to how to read these values out, I will publish them.
>>
> 
> You can use the exynos-chipid driver posted by Pankaj. Apply patches 1 and
> 2 from this series (http://www.spinics.net/lists/arm-kernel/msg548384.html)
> and then this diff to get the values of the registers that Krzysztof asked:
> 
Thanks for the code.

XU4:	 [    0.080039] Exynos: CPU[EXYNOS5800] CPU_REV[0x1] PKG_ID[0x1c04832a] AUX_INFO[0x43] 
XU3:	 [    0.080034] Exynos: CPU[EXYNOS5800] CPU_REV[0x1] PKG_ID[0x1604832a] AUX_INFO[0x43] 
XU3-lite:[    0.080033] Exynos: CPU[EXYNOS5800] CPU_REV[0x1] PKG_ID[0x5a12832a] AUX_INFO[0x13000054] 

Servus,
--
Markus Reichl

> diff --git a/drivers/soc/samsung/exynos-chipid.c b/drivers/soc/samsung/exynos-chipid.c
> index cf0128b18ee2..49fa76ec6d49 100644
> --- a/drivers/soc/samsung/exynos-chipid.c
> +++ b/drivers/soc/samsung/exynos-chipid.c
> @@ -22,6 +22,9 @@
>  #define EXYNOS_MAINREV_MASK	(0xF << 0)
>  #define EXYNOS_REV_MASK		(EXYNOS_SUBREV_MASK | EXYNOS_MAINREV_MASK)
>  
> +#define EXYNOS_PKG_ID		0x04
> +#define EXYNOS_AUX_INFO		0x1C
> +
>  static const struct exynos_soc_id {
>  	const char *name;
>  	unsigned int id;
> @@ -71,6 +74,8 @@ int __init exynos_chipid_early_init(void)
>  	const struct of_device_id *match;
>  	u32 product_id;
>  	u32 revision;
> +	u32 pkg_id;
> +	u32 aux_info;
>  
>  	np = of_find_matching_node_and_match(NULL,
>  			of_exynos_chipid_ids, &match);
> @@ -84,6 +89,8 @@ int __init exynos_chipid_early_init(void)
>  
>  	product_id  = readl_relaxed(exynos_chipid_base);
>  	revision = product_id & EXYNOS_REV_MASK;
> +	pkg_id = readl_relaxed(exynos_chipid_base + EXYNOS_PKG_ID);
> +	aux_info = readl_relaxed(exynos_chipid_base + EXYNOS_AUX_INFO);
>  	iounmap(exynos_chipid_base);
>  
>  	soc_dev_attr = kzalloc(sizeof(*soc_dev_attr), GFP_KERNEL);
> @@ -100,8 +107,8 @@ int __init exynos_chipid_early_init(void)
>  	soc_dev_attr->soc_id = product_id_to_soc_id(product_id);
>  
>  
> -	pr_info("Exynos: CPU[%s] CPU_REV[0x%x] Detected\n",
> -			product_id_to_soc_id(product_id), revision);
> +	pr_info("Exynos: CPU[%s] CPU_REV[0x%x] PKG_ID[0x%x] AUX_INFO[0x%x] \n",
> +		product_id_to_soc_id(product_id), revision, pkg_id, aux_info);
>  
>  	soc_dev = soc_device_register(soc_dev_attr);
>  	if (IS_ERR(soc_dev)) {
> 
> Best regards,
>