netdev - RE: [EXT] Re: [net v3 PATCH 1/1] net: mvpp2: clear BM pool before initialization

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Date: Fri, 19 Jan 2024 03:58:02 +0000
From: "Jenishkumar Patel [C]" <jpatel2@...vell.com>
To: 'Maxime Chevallier' <maxime.chevallier@...tlin.com>
CC: "marcin.s.wojtas@...il.com" <marcin.s.wojtas@...il.com>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "davem@...emloft.net"
	<davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Antoine Tenart
	<atenart@...nel.org>
Subject: RE: [EXT] Re: [net v3 PATCH 1/1] net: mvpp2: clear BM pool before
 initialization



-----Original Message-----
From: Maxime Chevallier <maxime.chevallier@...tlin.com> 
Sent: Thursday, January 18, 2024 8:21 PM
To: Jenishkumar Patel [C] <jpatel2@...vell.com>
Cc: marcin.s.wojtas@...il.com; linux@...linux.org.uk; davem@...emloft.net; edumazet@...gle.com; kuba@...nel.org; pabeni@...hat.com; netdev@...r.kernel.org; linux-kernel@...r.kernel.org; Antoine Tenart <atenart@...nel.org>
Subject: [EXT] Re: [net v3 PATCH 1/1] net: mvpp2: clear BM pool before initialization

External Email

----------------------------------------------------------------------
Hello,

On Thu, 18 Jan 2024 00:14:47 -0800
Jenishkumar Maheshbhai Patel <jpatel2@...vell.com> wrote:

> Register value persist after booting the kernel using kexec which 
> results in kernel panic. Thus clear the BM pool registers before 
> initialisation to fix the issue.

[...]

> +/* Cleanup pool before actual initialization in the OS */ static void 
> +mvpp2_bm_pool_cleanup(struct mvpp2 *priv, int pool_id) {
> +	u32 val;
> +	int i;
> +	unsigned int thread = mvpp2_cpu_to_thread(priv, get_cpu());

Please sort these lines with the longest line at the top, following the reverse christmas-tree style.
Thank you for the input will make the changes in v4
> +
> +	/* Drain the BM from all possible residues left by firmware */
> +	for (i = 0; i < MVPP2_BM_POOL_SIZE_MAX; i++)
> +		mvpp2_thread_read(priv, thread, MVPP2_BM_PHY_ALLOC_REG(pool_id));

Since you don't need to use the thread-based accessors after this, you can call put_cpu() right now to avoid keeping preemption disabled unnecessarily for too long.
Thank you for the input will make the changes in v4
> +	/* Stop the BM pool */
> +	val = mvpp2_read(priv, MVPP2_BM_POOL_CTRL_REG(pool_id));
> +	val |= MVPP2_BM_STOP_MASK;
> +	mvpp2_write(priv, MVPP2_BM_POOL_CTRL_REG(pool_id), val);
> +
> +	/* Mask BM all interrupts */
> +	mvpp2_write(priv, MVPP2_BM_INTR_MASK_REG(pool_id), 0);
> +
> +	/* Clear BM cause register */
> +	mvpp2_write(priv, MVPP2_BM_INTR_CAUSE_REG(pool_id), 0);

These two registers dealing with interrupt masking and cause are already cleared in mvpp2_bm_init(), not shown in the diff context, so either you can remove these or the ones in mvpp2_bm_init().
Thank you for the input will make the changes in v4
> +	put_cpu();
> +}
> +
>  static int mvpp2_bm_init(struct device *dev, struct mvpp2 *priv)  {
>  	enum dma_data_direction dma_dir = DMA_FROM_DEVICE;
>  	int i, err, poolnum = MVPP2_BM_POOLS_NUM;
>  	struct mvpp2_port *port;
>  
> +	if (priv->percpu_pools)
> +		poolnum = mvpp2_get_nrxqs(priv) * 2;
> +
> +	/* Clean up the pool state in case it contains stale state */
> +	for (i = 0; i < poolnum; i++)
> +		mvpp2_bm_pool_cleanup(priv, i);
> +
>  	if (priv->percpu_pools) {
>  		for (i = 0; i < priv->port_count; i++) {
>  			port = priv->port_list[i];
> @@ -629,7 +661,6 @@ static int mvpp2_bm_init(struct device *dev, struct mvpp2 *priv)
>  			}
>  		}
>  
> -		poolnum = mvpp2_get_nrxqs(priv) * 2;
>  		for (i = 0; i < poolnum; i++) {
>  			/* the pool in use */
>  			int pn = i / (poolnum / 2);

Thanks,

Maxime