Re: [PATCH] net: stmmac: fix FPE events losing

[Andrew Lunn]

On Tue, Nov 14, 2023 at 11:07:34AM +0000, Jianheng Zhang wrote:
> The 32-bit access of register MAC_FPE_CTRL_STS may clear the FPE status
> bits unexpectedly. Use 8-bit access for MAC_FPE_CTRL_STS control bits to
> avoid unexpected access of MAC_FPE_CTRL_STS status bits that can reduce
> the FPE handshake retries.
> 
> The bit[19:17] of register MAC_FPE_CTRL_STS are status register bits.
> Those bits are clear on read (or write of 1 when RCWE bit in
> MAC_CSR_SW_Ctrl register is set). Using 32-bit access for
> MAC_FPE_CTRL_STS control bits makes side effects that clear the status
> bits. Then the stmmac interrupt handler missing FPE event status and
> leads to FPE handshake failure and retries.

Is it possible to call the core of stmmac_fpe_irq_status() to extract
the information from these bits and then call
stmmac_fpe_event_status()?

Alternatively, can you actually set RCWE in MAC_CSR_SW_Ctrl and add a
mask to dwmac5_fpe_configure() etc so they don't write 1 to these
bits? That seems safer than assuming 8 bit reads work.

      Andrew