linux-kernel - Re: [PATCH v2 2/5] firmware: add support for ARM System Control and Power Interface(SCPI) protocol

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Date:	Wed, 20 May 2015 12:17:16 +0100
From:	"Jon Medhurst (Tixy)" <tixy@...aro.org>
To:	Sudeep Holla <sudeep.holla@....com>
Cc:	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Liviu Dudau <Liviu.Dudau@....com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Jassi Brar <jassisinghbrar@...il.com>
Subject: Re: [PATCH v2 2/5] firmware: add support for ARM System Control and
 Power Interface(SCPI) protocol

On Thu, 2015-05-14 at 16:42 +0100, Sudeep Holla wrote:
> This patch adds support for System Control and Power Interface (SCPI)
> Message Protocol used between the Application Cores(AP) and the System
> Control Processor(SCP). The MHU peripheral provides a mechanism for
> inter-processor communication between SCP's M3 processor and AP.
> 
> SCP offers control and management of the core/cluster power states,
> various power domain DVFS including the core/cluster, certain system
> clocks configuration, thermal sensors and many others.
> 
> This protocol driver provides interface for all the client drivers using
> SCPI to make use of the features offered by the SCP.
> 
> Signed-off-by: Sudeep Holla <sudeep.holla@....com>
> CC: Jassi Brar <jassisinghbrar@...il.com>
> Cc: Liviu Dudau <Liviu.Dudau@....com>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
> Cc: Jon Medhurst (Tixy) <tixy@...aro.org>
> ---

Sorry for the delay in looking at this. I have one nitpick below but
anyway, here's a

Reviewed-by: Jon Medhurst (Tixy) <tixy@...aro.org>

[...]
> +++ b/drivers/firmware/arm_scpi.c
[...]
> +static void scpi_process_cmd(struct scpi_chan *ch, u32 cmd)
> +{
> +	unsigned long flags;
> +	struct scpi_xfer *t, *match = NULL;
> +
> +	spin_lock_irqsave(&ch->rx_lock, flags);
> +	if (list_empty(&ch->rx_pending)) {
> +		spin_unlock_irqrestore(&ch->rx_lock, flags);
> +		return;
> +	}
> +
> +	list_for_each_entry(t, &ch->rx_pending, node)
> +		if (CMD_XTRACT_UNIQ(t->cmd) == CMD_XTRACT_UNIQ(cmd)) {
> +			list_del(&t->node);
> +			match = t;
> +			break;
> +		}
> +	/* check if wait_for_completion is in progress or timed-out */
> +	if (match && !completion_done(&match->done)) {
> +		struct scpi_shared_mem *mem = ch->rx_payload;
> +		int len = min(match->rx_len, CMD_SIZE(cmd));
> +
> +		match->status = le32_to_cpu(mem->status);
> +		memcpy_fromio(match->rx_buf, mem->payload, len);
> +		if (match->rx_len > len)

rx_len is unsigned and len is signed and so I had to go refresh my
memory from the C standard before I could convince myself that this if
statement was OK. Might be clearer if len was unsigned, especially as
it's the 'min' of two unsigned values.

-- 
Tixy

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