netdev - Re: [PATCH net 2/4] net: dsa: mv88e6xxx: Give chips more time to activate their PPUs

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Message-ID: <518b8e8c-aa84-4e8e-9780-a672915443e7@lunn.ch>
Date: Fri, 6 Dec 2024 14:18:04 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Tobias Waldekranz <tobias@...dekranz.com>
Cc: davem@...emloft.net, kuba@...nel.org, f.fainelli@...il.com,
	olteanv@...il.com, netdev@...r.kernel.org, linux@...linux.org.uk,
	chris.packham@...iedtelesis.co.nz
Subject: Re: [PATCH net 2/4] net: dsa: mv88e6xxx: Give chips more time to
 activate their PPUs

On Fri, Dec 06, 2024 at 02:07:34PM +0100, Tobias Waldekranz wrote:
> In a daisy-chain of three 6393X devices, delays of up to 750ms are
> sometimes observed before completion of PPU initialization (Global 1,
> register 0, bit 15) is signaled. Therefore, allow chips more time
> before giving up.
>  static int mv88e6352_g1_wait_ppu_polling(struct mv88e6xxx_chip *chip)
>  {
>  	int bit = __bf_shf(MV88E6352_G1_STS_PPU_STATE);
> +	int err, i;
>  
> -	return mv88e6xxx_g1_wait_bit(chip, MV88E6XXX_G1_STS, bit, 1);
> +	for (i = 0; i < 20; i++) {
> +		err = _mv88e6xxx_wait_bit(chip, chip->info->global1_addr,
> +					  MV88E6XXX_G1_STS, bit, 1, NULL);
> +		if (err != -ETIMEDOUT)
> +			break;
> +	}

The commit message does not indicate why it is necessary to swap to
_mv88e6xxx_wait_bit().

> +
> +	if (err) {
> +		dev_err(chip->dev, "PPU did not come online: %d\n", err);
> +		return err;
> +	}
> +
> +	if (i)
> +		dev_warn(chip->dev,
> +			 "PPU was slow to come online, retried %d times\n", i);

dev_dbg()? Does the user care if it took longer than one loop
iteration?

	Andrew