From: Florian Fainelli <f.fainelli@gmail•com>
To: Shenwei Wang <shenwei.wang@nxp•com>,
"David S. Miller" <davem@davemloft•net>,
Eric Dumazet <edumazet@google•com>,
Jakub Kicinski <kuba@kernel•org>, Paolo Abeni <pabeni@redhat•com>,
Shawn Guo <shawnguo@kernel•org>,
Sascha Hauer <s.hauer@pengutronix•de>,
Maxime Coquelin <mcoquelin.stm32@gmail•com>
Cc: Alexandre Torgue <alexandre.torgue@foss•st.com>,
Jose Abreu <joabreu@synopsys•com>,
Pengutronix Kernel Team <kernel@pengutronix•de>,
Fabio Estevam <festevam@gmail•com>,
NXP Linux Team <linux-imx@nxp•com>,
netdev@vger•kernel.org, linux-arm-kernel@lists•infradead.org,
linux-stm32@st-md-mailman•stormreply.com, imx@lists•linux.dev,
Mario Castaneda <mario.ignacio.castaneda.lopez@nxp•com>
Subject: Re: [PATCH net] net: stmmac: dwmac-imx: request high frequency mode
Date: Wed, 4 Oct 2023 13:00:04 -0700 [thread overview]
Message-ID: <643c55ca-4eca-4dfc-9176-cf46c2504057@gmail.com> (raw)
In-Reply-To: <20231004195442.414766-1-shenwei.wang@nxp.com>
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>
--
Florian
next prev parent reply other threads:[~2023-10-04 20:00 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-04 19:54 [PATCH net] net: stmmac: dwmac-imx: request high frequency mode Shenwei Wang
2023-10-04 20:00 ` Florian Fainelli [this message]
2023-10-04 20:16 ` Shenwei Wang
2023-10-04 21:59 ` Jakub Kicinski
2023-10-05 3:09 ` Andrew Lunn
2023-10-05 6:28 ` [Linux-stm32] " Ahmad Fatoum
2023-10-05 14:56 ` [EXT] " Shenwei Wang
2023-10-05 10:42 ` kernel test robot
2023-10-24 16:16 ` kernel test robot
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