netdev - Re: [PATCH v3 6/7] net: pch_gbe: Allow longer for resets

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Date:   Tue, 6 Jun 2017 16:10:14 +0200
From:   Marcin Nowakowski <marcin.nowakowski@...tec.com>
To:     Paul Burton <paul.burton@...tec.com>, <netdev@...r.kernel.org>
CC:     Tobias Klauser <tklauser@...tanz.ch>,
        "David S . Miller" <davem@...emloft.net>,
        Jarod Wilson <jarod@...hat.com>, <linux-mips@...ux-mips.org>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH v3 6/7] net: pch_gbe: Allow longer for resets

Hi Paul,

On 03.06.2017 01:40, Paul Burton wrote:
> Resets of the EG20T MAC on the MIPS Boston development board take longer
> than the 1000 loops that pch_gbe_wait_clr_bit was performing. Rather
> than simply increasing the number of loops, switch to using
> readl_poll_timeout_atomic() from linux/iopoll.h in order to provide some
> independence from the speed of the CPU.
> 
>   #define DRV_VERSION     "1.01"
> @@ -318,13 +319,11 @@ s32 pch_gbe_mac_read_mac_addr(struct pch_gbe_hw *hw)
>    */
>   static void pch_gbe_wait_clr_bit(void *reg, u32 bit)
>   {
> +	int err;
>   	u32 tmp;
>   
> -	/* wait busy */
> -	tmp = 1000;
> -	while ((ioread32(reg) & bit) && --tmp)
> -		cpu_relax();
> -	if (!tmp)
> +	err = readl_poll_timeout_atomic(reg, tmp, !(tmp & bit), 10, 500);
> +	if (err)
>   		pr_err("Error: busy bit is not cleared\n");
>   }

This new timeout value appears to be too low - I'm seeing plenty of 
timeout warnings now and ultimately the device fails to initialise:

[    7.541876] pch_gbe: EG20T PCH Gigabit Ethernet Driver - version 1.01
[    7.566451] pch_gbe: Error: busy bit is not cleared
[    7.572654] pch_gbe: Error: busy bit is not cleared
[    7.578727] pch_gbe: Error: busy bit is not cleared
[    7.587814] pch_gbe 0000:02:00.1: Invalid MAC address, interface 
disabled.
[    7.595605] pch_gbe 0000:02:00.1: MAC address : 00:00:00:00:00:00
[    7.606451] pch_gbe: Error: busy bit is not cleared
[    7.612572] pch_gbe: Error: busy bit is not cleared
[    7.618618] pch_gbe: Error: busy bit is not cleared
<...>
[   10.063351] pch_gbe 0000:02:00.1 eth0: Error: Invalid MAC address
[   10.074713] pch_gbe: Error: busy bit is not cleared
[   10.081030] pch_gbe: Error: busy bit is not cleared
[   10.087178] pch_gbe: Error: busy bit is not cleared
[   10.093328] pch_gbe: Error: busy bit is not cleared
[   10.100883] pch_gbe 0000:02:00.1 eth0: Error End
[   10.106272] IP-Config: Failed to open eth0

My tests show that a timeout value as big as 20000 may be required to 
make it work reliably ...

Marcin