Re: [lwip-users] Low Iperf performance of lwip 1.4.1 on STM32 and FreeRTOS

[Claudius Zingerli]

Hi ella and all,

Some progress here: I receive a lot of CRC & Align errors (MMC counters 
of STM32). At least there is /some/ correlation between these errors and 
LWIP behaving strangely (if there is an increase in the MMC counters, 
LwIP gets into trouble, if there is none, LwIP mostly works fine). This 
may further be related to the usage of RMII between the MAC and PHY and 
creating the RMII-Clock with the STM32-PLL. Datasheet jitter and 
precision should be OK for the PHY, but this might not be the cleanest 
solution (There is some hint in the datasheet that good guys should 
source the RMII clock by bypassing the PLL). So in a next step, I'm 
going to use a dedicated 50MHz oscillator to clock the PHY and MCU.
On the software-side: An own implementation of the MAC driver is on the 
way. Could probably be open sourced if there is some interest.

Claudius


On 6/23/2013 7:16 AM, ella wrote:
> The problem is not FreeRTOS but buggy and ugly STM32 netif driver. I have
> studied original driver provided by ST and had nothing but rewrite it.
>
> Just one example of wrong architecture of this driver. This is from
> low_level_output():
>
>      buffer =  (u8 *)(DMATxDescToSet->Buffer1Addr);
>      for(q = p; q != NULL; q = q->next)
>      {
>        memcpy((u8_t*)&buffer[l], q->payload, q->len);
>        l = l + q->len;
>      }
>
> Consider that buffers are allocated as
> extern uint8_t Tx_Buff[ETH_TXBUFNB][ETH_TX_BUF_SIZE];
> and are linked to chained DMA descriptors.
>
> If packet size bigger then ETH_TX_BUF_SIZE you are at potential danger of
> wrap around that is not treated in code. Same happens for RX flow. So no
> surprise you have a problems with big packets.
> And this is only one place, there is a number of others. There are also a
> few races.
> In short DO NOT USE THIS DRIVER.
>
>
>
>
>
> --
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> http://lwip.100.n7.nabble.com/Low-Iperf-performance-of-lwip-1-4-1-on-STM32-and-FreeRTOS-tp21579p21581.html
> Sent from the lwip-users mailing list archive at Nabble.com.
>
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