[PATCH net] net: stmmac: dwmac-imx: request high frequency mode

[PATCH net] net: stmmac: dwmac-imx: request high frequency mode

[Shenwei Wang]

Some i.MX SoCs like the i.mx8mq support adjusting the frequency of the
DDR, AHB, and AXI buses based on system loading. If the dwmac interface
in the driver does not request a HIGH frequency, it can significantly
degrade performance when the system switches to a lower frequency to
conserve power.

For example, on an i.MX8MQ EVK board, the throughput dropped to around
100Mbit/s on a 1Gbit connection:

    [ ID] Interval           Transfer     Bitrate
    [  5]   0.00-10.00  sec   117 MBytes  97.9 Mbits/sec

However, throughput can return to expected levels after its driver requests
the high frequency mode. Requesting high frequency in the dwmac driver is
essential to maintain full throughput when the i.MX SoC adjusts bus speeds
for power savings.

Signed-off-by: Mario Castaneda <mario.ignacio.castaneda.lopez@nxp.com>
Signed-off-by: Shenwei Wang <shenwei.wang@nxp.com>
Tested-by: Mario Castaneda <mario.ignacio.castaneda.lopez@nxp.com>
---
 drivers/net/ethernet/stmicro/stmmac/dwmac-imx.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-imx.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-imx.c
index 8f730ada71f91..ba6ae0465ecaa 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-imx.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-imx.c
@@ -6,6 +6,7 @@
  *
  */
 
+#include <linux/busfreq-imx.h>
 #include <linux/clk.h>
 #include <linux/gpio/consumer.h>
 #include <linux/kernel.h>
@@ -152,7 +153,9 @@ static int imx_dwmac_clks_config(void *priv, bool enabled)
 			clk_disable_unprepare(dwmac->clk_mem);
 			return ret;
 		}
+		request_bus_freq(BUS_FREQ_HIGH);
 	} else {
+		release_bus_freq(BUS_FREQ_HIGH);
 		clk_disable_unprepare(dwmac->clk_tx);
 		clk_disable_unprepare(dwmac->clk_mem);
 	}
-- 
2.34.1


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Re: [PATCH net] net: stmmac: dwmac-imx: request high frequency mode

[Florian Fainelli]

On 10/4/23 12:54, Shenwei Wang wrote:
> Some i.MX SoCs like the i.mx8mq support adjusting the frequency of the
> DDR, AHB, and AXI buses based on system loading. If the dwmac interface
> in the driver does not request a HIGH frequency, it can significantly
> degrade performance when the system switches to a lower frequency to
> conserve power.
> 
> For example, on an i.MX8MQ EVK board, the throughput dropped to around
> 100Mbit/s on a 1Gbit connection:
> 
>      [ ID] Interval           Transfer     Bitrate
>      [  5]   0.00-10.00  sec   117 MBytes  97.9 Mbits/sec
> 
> However, throughput can return to expected levels after its driver requests
> the high frequency mode. Requesting high frequency in the dwmac driver is
> essential to maintain full throughput when the i.MX SoC adjusts bus speeds
> for power savings.
> 
> Signed-off-by: Mario Castaneda <mario.ignacio.castaneda.lopez@nxp.com>
> Signed-off-by: Shenwei Wang <shenwei.wang@nxp.com>
> Tested-by: Mario Castaneda <mario.ignacio.castaneda.lopez@nxp.com>

I assume that you cannot go full dynamic and adjust the bus frequency 
based upon the negotiated link speed? There may be a need to adjust the 
bus frequency prior to starting any DMA transfers, otherwise dynamic 
frequency scaling of the bus may cause all sorts of issues?

Regardless of the answer:

Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
-- 
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Re: [PATCH net] net: stmmac: dwmac-imx: request high frequency mode

[Shenwei Wang]

> -----Original Message-----
> From: Florian Fainelli <f.fainelli@gmail.com>
> Sent: Wednesday, October 4, 2023 3:00 PM
> To: Shenwei Wang <shenwei.wang@nxp.com>; David S. Miller
> > Signed-off-by: Mario Castaneda <mario.ignacio.castaneda.lopez@nxp.com>
> > Signed-off-by: Shenwei Wang <shenwei.wang@nxp.com>
> > Tested-by: Mario Castaneda <mario.ignacio.castaneda.lopez@nxp.com>
> 
> I assume that you cannot go full dynamic and adjust the bus frequency based
> upon the negotiated link speed? There may be a need to adjust the bus
> frequency prior to starting any DMA transfers, otherwise dynamic frequency
> scaling of the bus may cause all sorts of issues?

Once BUS_FREQ_HIGH is requested, the system will not change the bus frequency 
when transitioning to a low power state. 
The hardware supports glitch-free frequency scaling, so blocks like DMA will not be 
affected during bus frequency adjustments.

Regards,
Shenwei
 
> 
> Regardless of the answer:
> 
> Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
> --
> Florian

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Re: [PATCH net] net: stmmac: dwmac-imx: request high frequency mode

[Jakub Kicinski]

On Wed,  4 Oct 2023 14:54:42 -0500 Shenwei Wang wrote:
> Some i.MX SoCs like the i.mx8mq support adjusting the frequency of the
> DDR, AHB, and AXI buses based on system loading. If the dwmac interface
> in the driver does not request a HIGH frequency, it can significantly
> degrade performance when the system switches to a lower frequency to
> conserve power.
> 
> For example, on an i.MX8MQ EVK board, the throughput dropped to around
> 100Mbit/s on a 1Gbit connection:
> 
>     [ ID] Interval           Transfer     Bitrate
>     [  5]   0.00-10.00  sec   117 MBytes  97.9 Mbits/sec
> 
> However, throughput can return to expected levels after its driver requests
> the high frequency mode. Requesting high frequency in the dwmac driver is
> essential to maintain full throughput when the i.MX SoC adjusts bus speeds
> for power savings.

Oh, another one in one day :S Although this one feels much more like
a bug that escaped testing because testing didn't use power saving?
In any case, do you happen to have a user report you can mention here?
Quoting stable rules:

| Serious issues as reported by a user of a distribution kernel may also
| be considered if they fix a notable performance or interactivity
| issue. As these fixes are not as obvious and have a higher risk of a
| subtle regression they should only be submitted by a distribution
| kernel maintainer and include an addendum linking to a bugzilla entry
| if it exists and additional information on the user-visible impact.

And a Fixes tag would be good, please add.
-- 
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Re: [PATCH net] net: stmmac: dwmac-imx: request high frequency mode

[Andrew Lunn]

On Wed, Oct 04, 2023 at 02:54:42PM -0500, Shenwei Wang wrote:
> Some i.MX SoCs like the i.mx8mq support adjusting the frequency of the
> DDR, AHB, and AXI buses based on system loading. If the dwmac interface
> in the driver does not request a HIGH frequency, it can significantly
> degrade performance when the system switches to a lower frequency to
> conserve power.
> 
> For example, on an i.MX8MQ EVK board, the throughput dropped to around
> 100Mbit/s on a 1Gbit connection:
> 
>     [ ID] Interval           Transfer     Bitrate
>     [  5]   0.00-10.00  sec   117 MBytes  97.9 Mbits/sec
> 
> However, throughput can return to expected levels after its driver requests
> the high frequency mode. Requesting high frequency in the dwmac driver is
> essential to maintain full throughput when the i.MX SoC adjusts bus speeds
> for power savings.

Isn't this going to cause a power regression? I expect there are
applications which expect this behaviour and are happy with
100Mbps. And you are going to change it so their battery goes flatter
faster, or they need to run their fan more often. So maybe you need a
DT property to always forcing high speed.

And as Florian pointed out, maybe you should look at the negotiated
speed, and if you have a 10 or 100Mbps link, the MAC does not need
high frequency, so why not allow it to be low and safe some power.

     Andrew

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Re: [Linux-stm32] [PATCH net] net: stmmac: dwmac-imx: request high frequency mode

[Ahmad Fatoum]

Hello Shenwei,

On 04.10.23 21:54, Shenwei Wang wrote:
> Some i.MX SoCs like the i.mx8mq support adjusting the frequency of the
> DDR, AHB, and AXI buses based on system loading. If the dwmac interface
> in the driver does not request a HIGH frequency, it can significantly
> degrade performance when the system switches to a lower frequency to
> conserve power.
> 
> For example, on an i.MX8MQ EVK board, the throughput dropped to around
> 100Mbit/s on a 1Gbit connection:
> 
>     [ ID] Interval           Transfer     Bitrate
>     [  5]   0.00-10.00  sec   117 MBytes  97.9 Mbits/sec
> 
> However, throughput can return to expected levels after its driver requests
> the high frequency mode. Requesting high frequency in the dwmac driver is
> essential to maintain full throughput when the i.MX SoC adjusts bus speeds
> for power savings.
> 
> Signed-off-by: Mario Castaneda <mario.ignacio.castaneda.lopez@nxp.com>
> Signed-off-by: Shenwei Wang <shenwei.wang@nxp.com>
> Tested-by: Mario Castaneda <mario.ignacio.castaneda.lopez@nxp.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/dwmac-imx.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-imx.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-imx.c
> index 8f730ada71f91..ba6ae0465ecaa 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-imx.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-imx.c
> @@ -6,6 +6,7 @@
>   *
>   */
>  
> +#include <linux/busfreq-imx.h>
>  #include <linux/clk.h>
>  #include <linux/gpio/consumer.h>
>  #include <linux/kernel.h>
> @@ -152,7 +153,9 @@ static int imx_dwmac_clks_config(void *priv, bool enabled)
>  			clk_disable_unprepare(dwmac->clk_mem);
>  			return ret;
>  		}
> +		request_bus_freq(BUS_FREQ_HIGH);

I don't find request_bus_freq in linux-next (next-20231005). AFAIK, it was only ever
suggested as RFC and never went beyond that as a reimplmeentation on top of devfreq
was requested instead of the i.MX-specific API used in the vendor fork.

Did you observe this performance pregression with mainline?

Cheers,
Ahmad


>  	} else {
> +		release_bus_freq(BUS_FREQ_HIGH);
>  		clk_disable_unprepare(dwmac->clk_tx);
>  		clk_disable_unprepare(dwmac->clk_mem);
>  	}

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RE: [EXT] Re: [Linux-stm32] [PATCH net] net: stmmac: dwmac-imx: request high frequency mode

[Shenwei Wang]

> -----Original Message-----
> From: Ahmad Fatoum <a.fatoum@pengutronix.de>
> Sent: Thursday, October 5, 2023 1:28 AM
> To: Shenwei Wang <shenwei.wang@nxp.com>; David S. Miller
> >                       clk_disable_unprepare(dwmac->clk_mem);
> >                       return ret;
> >               }
> > +             request_bus_freq(BUS_FREQ_HIGH);
>
> I don't find request_bus_freq in linux-next (next-20231005). AFAIK, it was only
> ever suggested as RFC and never went beyond that as a reimplmeentation on
> top of devfreq was requested instead of the i.MX-specific API used in the vendor
> fork.
>
> Did you observe this performance pregression with mainline?

My apologies. I did not realize I was working on a wrong working tree. The busfreq-imx
driver hasn't yet gotten upstreamed.

Please ignore this patch.

Regards,
Shenwei

>
> Cheers,
> Ahmad
>
>
> >       } else {
> > +             release_bus_freq(BUS_FREQ_HIGH);
> >               clk_disable_unprepare(dwmac->clk_tx);
> >               clk_disable_unprepare(dwmac->clk_mem);
> >       }
>
> --
> Pengutronix e.K.                           |                             |
> Steuerwalder Str. 21                       |
> http://www.pen/
> gutronix.de%2F&data=05%7C01%7Cshenwei.wang%40nxp.com%7Cbab522390
> 5f542a0cabb08dbc56c406d%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C
> 0%7C638320840957133285%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjA
> wMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%
> 7C&sdata=kxhSaLbYLmFqYkbN%2BXg1lHfwRbRgWrSNy35BMpcMnSk%3D&reser
> ved=0  |
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Re: [PATCH net] net: stmmac: dwmac-imx: request high frequency mode

[kernel test robot]

Hi Shenwei,

kernel test robot noticed the following build errors:

[auto build test ERROR on net/main]

url:    https://github.com/intel-lab-lkp/linux/commits/Shenwei-Wang/net-stmmac-dwmac-imx-request-high-frequency-mode/20231005-035606
base:   net/main
patch link:    https://lore.kernel.org/r/20231004195442.414766-1-shenwei.wang%40nxp.com
patch subject: [PATCH net] net: stmmac: dwmac-imx: request high frequency mode
config: alpha-allyesconfig (https://download.01.org/0day-ci/archive/20231005/202310051811.Rltsgr8J-lkp@intel.com/config)
compiler: alpha-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231005/202310051811.Rltsgr8J-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202310051811.Rltsgr8J-lkp@intel.com/

All errors (new ones prefixed by >>):

>> drivers/net/ethernet/stmicro/stmmac/dwmac-imx.c:9:10: fatal error: linux/busfreq-imx.h: No such file or directory
       9 | #include <linux/busfreq-imx.h>
         |          ^~~~~~~~~~~~~~~~~~~~~
   compilation terminated.


vim +9 drivers/net/ethernet/stmicro/stmmac/dwmac-imx.c

   > 9	#include <linux/busfreq-imx.h>
    10	#include <linux/clk.h>
    11	#include <linux/gpio/consumer.h>
    12	#include <linux/kernel.h>
    13	#include <linux/mfd/syscon.h>
    14	#include <linux/module.h>
    15	#include <linux/of.h>
    16	#include <linux/of_net.h>
    17	#include <linux/phy.h>
    18	#include <linux/platform_device.h>
    19	#include <linux/pm_wakeirq.h>
    20	#include <linux/regmap.h>
    21	#include <linux/slab.h>
    22	#include <linux/stmmac.h>
    23	

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Re: [PATCH net] net: stmmac: dwmac-imx: request high frequency mode

[kernel test robot]

Hi Shenwei,

kernel test robot noticed the following build errors:

[auto build test ERROR on net/main]

url:    https://github.com/intel-lab-lkp/linux/commits/Shenwei-Wang/net-stmmac-dwmac-imx-request-high-frequency-mode/20231005-035606
base:   net/main
patch link:    https://lore.kernel.org/r/20231004195442.414766-1-shenwei.wang%40nxp.com
patch subject: [PATCH net] net: stmmac: dwmac-imx: request high frequency mode
config: arm-defconfig (https://download.01.org/0day-ci/archive/20231025/202310250045.xYg3qn6G-lkp@intel.com/config)
compiler: clang version 14.0.6 (https://github.com/llvm/llvm-project.git f28c006a5895fc0e329fe15fead81e37457cb1d1)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231025/202310250045.xYg3qn6G-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202310250045.xYg3qn6G-lkp@intel.com/

All errors (new ones prefixed by >>):

>> drivers/net/ethernet/stmicro/stmmac/dwmac-imx.c:9:10: fatal error: 'linux/busfreq-imx.h' file not found
   #include <linux/busfreq-imx.h>
            ^~~~~~~~~~~~~~~~~~~~~
   1 error generated.


vim +9 drivers/net/ethernet/stmicro/stmmac/dwmac-imx.c

   > 9	#include <linux/busfreq-imx.h>
    10	#include <linux/clk.h>
    11	#include <linux/gpio/consumer.h>
    12	#include <linux/kernel.h>
    13	#include <linux/mfd/syscon.h>
    14	#include <linux/module.h>
    15	#include <linux/of.h>
    16	#include <linux/of_net.h>
    17	#include <linux/phy.h>
    18	#include <linux/platform_device.h>
    19	#include <linux/pm_wakeirq.h>
    20	#include <linux/regmap.h>
    21	#include <linux/slab.h>
    22	#include <linux/stmmac.h>
    23	

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