[PATCH net] net: stmmac: dwmac-imx: request high frequency mode
Florian Fainelli
f.fainelli at gmail.com
Wed Oct 4 13:00:04 PDT 2023
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 at nxp.com>
> Signed-off-by: Shenwei Wang <shenwei.wang at nxp.com>
> Tested-by: Mario Castaneda <mario.ignacio.castaneda.lopez at 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 at broadcom.com>
--
Florian
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