[PATCH v3 1/2] powerpc/powernv: Enhance opal message read interface

[Oliver O'Halloran]

On Wed, 2019-08-21 at 13:43 +0530, Vasant Hegde wrote:
> Use "opal-msg-size" device tree property to allocate memory for "opal_msg".
> 
> Cc: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
> Cc: Jeremy Kerr <jk at ozlabs.org>
> Signed-off-by: Vasant Hegde <hegdevasant at linux.vnet.ibm.com>
> ---
> Changes in v3:
>   - Call BUG_ON, if we fail to allocate memory during init.
> 
> -Vasant
> 
>  arch/powerpc/platforms/powernv/opal.c | 29 ++++++++++++++++++---------
>  1 file changed, 19 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
> index aba443be7daa..4f1f68f568bf 100644
> --- a/arch/powerpc/platforms/powernv/opal.c
> +++ b/arch/powerpc/platforms/powernv/opal.c
> @@ -58,6 +58,8 @@ static DEFINE_SPINLOCK(opal_write_lock);
>  static struct atomic_notifier_head opal_msg_notifier_head[OPAL_MSG_TYPE_MAX];
>  static uint32_t opal_heartbeat;
>  static struct task_struct *kopald_tsk;
> +static struct opal_msg *opal_msg;
> +static uint64_t opal_msg_size;
>  
>  void opal_configure_cores(void)
>  {
> @@ -271,14 +273,9 @@ static void opal_message_do_notify(uint32_t msg_type, void *msg)
>  static void opal_handle_message(void)
>  {
>  	s64 ret;
> -	/*
> -	 * TODO: pre-allocate a message buffer depending on opal-msg-size
> -	 * value in /proc/device-tree.
> -	 */
> -	static struct opal_msg msg;
>  	u32 type;
>  
> -	ret = opal_get_msg(__pa(&msg), sizeof(msg));
> +	ret = opal_get_msg(__pa(opal_msg), opal_msg_size);
>  	/* No opal message pending. */
>  	if (ret == OPAL_RESOURCE)
>  		return;
> @@ -290,14 +287,14 @@ static void opal_handle_message(void)
>  		return;
>  	}
>  
> -	type = be32_to_cpu(msg.msg_type);
> +	type = be32_to_cpu(opal_msg->msg_type);
>  
>  	/* Sanity check */
>  	if (type >= OPAL_MSG_TYPE_MAX) {
>  		pr_warn_once("%s: Unknown message type: %u\n", __func__, type);
>  		return;
>  	}
> -	opal_message_do_notify(type, (void *)&msg);
> +	opal_message_do_notify(type, (void *)opal_msg);
>  }
>  
>  static irqreturn_t opal_message_notify(int irq, void *data)
> @@ -306,9 +303,21 @@ static irqreturn_t opal_message_notify(int irq, void *data)
>  	return IRQ_HANDLED;
>  }
>  
> -static int __init opal_message_init(void)
> +static int __init opal_message_init(struct device_node *opal_node)
>  {
>  	int ret, i, irq;

> +	const __be32 *val;
> +
> +	val = of_get_property(opal_node, "opal-msg-size", NULL);
> +	if (val)
> +		opal_msg_size = be32_to_cpup(val);

Use of_property_read_u32()

> +
> +	/* If opal-msg-size property is not available then use default size */
> +	if (!opal_msg_size)
> +		opal_msg_size = sizeof(struct opal_msg);
> +
> +	opal_msg = kmalloc(opal_msg_size, GFP_KERNEL);

> +	BUG_ON(opal_msg == NULL);

Seems questionable. Why not fall back to using a staticly allocated
struct opal_msg? Or re-try the allocation with the size limited to
sizeof(struct opal_msg)?

>  	for (i = 0; i < OPAL_MSG_TYPE_MAX; i++)
>  		ATOMIC_INIT_NOTIFIER_HEAD(&opal_msg_notifier_head[i]);
> @@ -910,7 +919,7 @@ static int __init opal_init(void)
>  	}
>  
>  	/* Initialise OPAL messaging system */
> -	opal_message_init();
> +	opal_message_init(opal_node);
>  
>  	/* Initialise OPAL asynchronous completion interface */
>  	opal_async_comp_init();