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Message-ID: <20230613163248.f6w5plluidqjmrzs@mercury.elektranox.org>
Date: Tue, 13 Jun 2023 18:32:48 +0200
From: Sebastian Reichel <sebastian.reichel@...labora.com>
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
Subject: Re: [PATCH v5 06/25] PM / devfreq: rockchip-dfi: Use free running
counter
Hi,
On Wed, May 24, 2023 at 10:31:34AM +0200, Sascha Hauer wrote:
> The DDR_MON counters are free running counters. These are resetted to 0
> when starting them over like currently done when reading the current
> counter values.
>
> Resetting the counters becomes a problem with perf support we want to
> add later, because perf needs counters that are not modified elsewhere.
>
> This patch removes resetting the counters and keeps them running
> instead. That means we no longer use the absolute counter values but
> instead compare them with the counter values we read last time. Not
> stopping the counters also has the impact that they are running while
> we are reading them. We cannot read multiple timers atomically, so
> the values do not exactly fit together. The effect should be negligible
> though as the time between two measurements is some orders of magnitude
> bigger than the time we need to read multiple registers.
>
> Signed-off-by: Sascha Hauer <s.hauer@...gutronix.de>
> ---
Reviewed-by: Sebastian Reichel <sebastian.reichel@...labora.com>
-- Sebastian
>
> Notes:
> Changes since v4:
> - rephrase commit message
> - Drop unused variable
>
> drivers/devfreq/event/rockchip-dfi.c | 52 ++++++++++++++++------------
> 1 file changed, 30 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/devfreq/event/rockchip-dfi.c b/drivers/devfreq/event/rockchip-dfi.c
> index 680f629da64fc..126bb744645b6 100644
> --- a/drivers/devfreq/event/rockchip-dfi.c
> +++ b/drivers/devfreq/event/rockchip-dfi.c
> @@ -38,11 +38,15 @@
> #define DDRMON_CH1_COUNT_NUM 0x3c
> #define DDRMON_CH1_DFI_ACCESS_NUM 0x40
>
> -struct dmc_usage {
> +struct dmc_count_channel {
> u32 access;
> u32 total;
> };
>
> +struct dmc_count {
> + struct dmc_count_channel c[RK3399_DMC_NUM_CH];
> +};
> +
> /*
> * The dfi controller can monitor DDR load. It has an upper and lower threshold
> * for the operating points. Whenever the usage leaves these bounds an event is
> @@ -51,7 +55,7 @@ struct dmc_usage {
> struct rockchip_dfi {
> struct devfreq_event_dev *edev;
> struct devfreq_event_desc desc;
> - struct dmc_usage ch_usage[RK3399_DMC_NUM_CH];
> + struct dmc_count last_event_count;
> struct device *dev;
> void __iomem *regs;
> struct regmap *regmap_pmu;
> @@ -85,30 +89,18 @@ static void rockchip_dfi_stop_hardware_counter(struct devfreq_event_dev *edev)
> writel_relaxed(SOFTWARE_DIS, dfi_regs + DDRMON_CTRL);
> }
>
> -static int rockchip_dfi_get_busier_ch(struct devfreq_event_dev *edev)
> +static void rockchip_dfi_read_counters(struct devfreq_event_dev *edev, struct dmc_count *count)
> {
> struct rockchip_dfi *dfi = devfreq_event_get_drvdata(edev);
> - u32 tmp, max = 0;
> - u32 i, busier_ch = 0;
> + u32 i;
> void __iomem *dfi_regs = dfi->regs;
>
> - rockchip_dfi_stop_hardware_counter(edev);
> -
> - /* Find out which channel is busier */
> for (i = 0; i < RK3399_DMC_NUM_CH; i++) {
> - dfi->ch_usage[i].access = readl_relaxed(dfi_regs +
> + count->c[i].access = readl_relaxed(dfi_regs +
> DDRMON_CH0_DFI_ACCESS_NUM + i * 20);
> - dfi->ch_usage[i].total = readl_relaxed(dfi_regs +
> + count->c[i].total = readl_relaxed(dfi_regs +
> DDRMON_CH0_COUNT_NUM + i * 20);
> - tmp = dfi->ch_usage[i].access;
> - if (tmp > max) {
> - busier_ch = i;
> - max = tmp;
> - }
> }
> - rockchip_dfi_start_hardware_counter(edev);
> -
> - return busier_ch;
> }
>
> static int rockchip_dfi_disable(struct devfreq_event_dev *edev)
> @@ -145,12 +137,28 @@ static int rockchip_dfi_get_event(struct devfreq_event_dev *edev,
> struct devfreq_event_data *edata)
> {
> struct rockchip_dfi *dfi = devfreq_event_get_drvdata(edev);
> - int busier_ch;
> + struct dmc_count count;
> + struct dmc_count *last = &dfi->last_event_count;
> + u32 access = 0, total = 0;
> + int i;
> +
> + 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;
> +
> + if (a > access) {
> + access = a;
> + total = t;
> + }
> + }
>
> - busier_ch = rockchip_dfi_get_busier_ch(edev);
> + edata->load_count = access * 4;
> + edata->total_count = total;
>
> - edata->load_count = dfi->ch_usage[busier_ch].access * 4;
> - edata->total_count = dfi->ch_usage[busier_ch].total;
> + dfi->last_event_count = count;
>
> return 0;
> }
> --
> 2.39.2
>
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