linux-kernel - Re: [PATCH v7 07/26] PM / devfreq: rockchip-dfi: introduce channel mask

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Date:   Tue, 17 Oct 2023 17:28:57 +0900
From:   Chanwoo Choi <chanwoo@...nel.org>
To:     Sascha Hauer <s.hauer@...gutronix.de>
Cc:     linux-rockchip@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, Heiko Stuebner <heiko@...ech.de>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>, kernel@...gutronix.de,
        Michael Riesch <michael.riesch@...fvision.net>,
        Robin Murphy <robin.murphy@....com>,
        Vincent Legoll <vincent.legoll@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>, devicetree@...r.kernel.org,
        Sebastian Reichel <sebastian.reichel@...labora.com>
Subject: Re: [PATCH v7 07/26] PM / devfreq: rockchip-dfi: introduce channel
 mask

On 23. 10. 16. 21:45, Sascha Hauer wrote:
> On Mon, Oct 16, 2023 at 01:22:16PM +0200, Sascha Hauer wrote:
>> On Sat, Oct 07, 2023 at 02:21:10AM +0900, Chanwoo Choi wrote:
>>> Hi,
>>>
>>> On 23. 7. 4. 18:32, Sascha Hauer wrote:
>>>> Different Rockchip SoC variants have a different number of channels.
>>>> Introduce a channel mask to make the number of channels configurable
>>>> from SoC initialization code.
>>>>
>>>> Reviewed-by: Sebastian Reichel <sebastian.reichel@...labora.com>
>>>> Signed-off-by: Sascha Hauer <s.hauer@...gutronix.de>
>>>> ---
>>>>  drivers/devfreq/event/rockchip-dfi.c | 23 +++++++++++++++++------
>>>>  1 file changed, 17 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/drivers/devfreq/event/rockchip-dfi.c b/drivers/devfreq/event/rockchip-dfi.c
>>>> index 126bb744645b6..82de24a027579 100644
>>>> --- a/drivers/devfreq/event/rockchip-dfi.c
>>>> +++ b/drivers/devfreq/event/rockchip-dfi.c
>>>> @@ -18,10 +18,11 @@
>>>>  #include <linux/list.h>
>>>>  #include <linux/of.h>
>>>>  #include <linux/of_device.h>
>>>> +#include <linux/bits.h>
>>>>  
>>>>  #include <soc/rockchip/rk3399_grf.h>
>>>>  
>>>> -#define RK3399_DMC_NUM_CH	2
>>>> +#define DMC_MAX_CHANNELS	2
>>>>  
>>>>  /* DDRMON_CTRL */
>>>>  #define DDRMON_CTRL	0x04
>>>> @@ -44,7 +45,7 @@ struct dmc_count_channel {
>>>>  };
>>>>  
>>>>  struct dmc_count {
>>>> -	struct dmc_count_channel c[RK3399_DMC_NUM_CH];
>>>> +	struct dmc_count_channel c[DMC_MAX_CHANNELS];
>>>>  };
>>>>  
>>>>  /*
>>>> @@ -61,6 +62,7 @@ struct rockchip_dfi {
>>>>  	struct regmap *regmap_pmu;
>>>>  	struct clk *clk;
>>>>  	u32 ddr_type;
>>>> +	unsigned int channel_mask;
>>>>  };
>>>>  
>>>>  static void rockchip_dfi_start_hardware_counter(struct devfreq_event_dev *edev)
>>>> @@ -95,7 +97,9 @@ static void rockchip_dfi_read_counters(struct devfreq_event_dev *edev, struct dm
>>>>  	u32 i;
>>>>  	void __iomem *dfi_regs = dfi->regs;
>>>>  
>>>> -	for (i = 0; i < RK3399_DMC_NUM_CH; i++) {
>>>> +	for (i = 0; i < DMC_MAX_CHANNELS; i++) {
>>>> +		if (!(dfi->channel_mask & BIT(i)))
>>>> +			continue;
>>>>  		count->c[i].access = readl_relaxed(dfi_regs +
>>>>  				DDRMON_CH0_DFI_ACCESS_NUM + i * 20);
>>>>  		count->c[i].total = readl_relaxed(dfi_regs +
>>>> @@ -145,9 +149,14 @@ static int rockchip_dfi_get_event(struct devfreq_event_dev *edev,
>>>>  	rockchip_dfi_read_counters(edev, &count);
>>>>  
>>>>  	/* We can only report one channel, so find the busiest one */
>>>> -	for (i = 0; i < RK3399_DMC_NUM_CH; i++) {
>>>> -		u32 a = count.c[i].access - last->c[i].access;
>>>> -		u32 t = count.c[i].total - last->c[i].total;
>>>> +	for (i = 0; i < DMC_MAX_CHANNELS; i++) {
>>>
>>> Instead of DMC_MAX_CHANNELS defintion,
>>> you can initialize the max channel in each rkXXXX_dfi_init() like 'dfi->channel_count'.
>>> It reduces the unnecessary loop by initializing the proper max channel.
>>
>> That is not easily possible. Some SoCs, eg the RK3588 have four
>> channels, but not all channels are necessarily enabled it also
>> might not be the first channels that are enabled. On a RK3588
>> the channel mask might for example be 0b0101.
> 
> Nah, forget this comment. Of course I can initialize a variable with a
> maximum value of channels that could be available on this SoC and only
> iterate over these. Will do.
> 

Thanks.

-- 
Best Regards,
Samsung Electronics
Chanwoo Choi