linux-kernel - Re: [PATCH v5 2/8] firmware: add support for ARM System Control and Power Interface(SCPI) protocol

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Date:	Wed, 29 Jul 2015 13:35:31 +0530
From:	Jassi Brar <jassisinghbrar@...il.com>
To:	Sudeep Holla <sudeep.holla@....com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Liviu Dudau <liviu.dudau@....com>,
	Punit Agrawal <punit.agrawal@....com>,
	"Jon Medhurst (Tixy)" <tixy@...aro.org>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
	Kevin Hilman <khilman@...nel.org>
Subject: Re: [PATCH v5 2/8] firmware: add support for ARM System Control and
 Power Interface(SCPI) protocol

On Thu, Jul 23, 2015 at 4:40 PM, Sudeep Holla <sudeep.holla@....com> wrote:

...

> +static int scpi_probe(struct platform_device *pdev)
> +{
> +       int count, idx, ret;
> +       struct resource res;
> +       struct scpi_chan *scpi_chan;
> +       struct device *dev = &pdev->dev;
> +       struct device_node *np = dev->of_node;
> +
> +       scpi_info = devm_kzalloc(dev, sizeof(*scpi_info), GFP_KERNEL);
> +       if (!scpi_info)
> +               return -ENOMEM;
> +
> +       count = of_count_phandle_with_args(np, "mboxes", "#mbox-cells");
> +       if (count < 0) {
> +               dev_err(dev, "no mboxes property in '%s'\n", np->full_name);
> +               return -ENODEV;
> +       }
> +
> +       scpi_chan = devm_kcalloc(dev, count, sizeof(*scpi_chan), GFP_KERNEL);
> +       if (!scpi_chan)
> +               return -ENOMEM;
> +
> +       for (idx = 0; idx < count; idx++) {
> +               resource_size_t size;
> +               struct scpi_chan *pchan = scpi_chan + idx;
> +               struct mbox_client *cl = &pchan->cl;
> +               struct device_node *shmem = of_parse_phandle(np, "shmem", idx);
> +
> +               if (of_address_to_resource(shmem, 0, &res)) {
> +                       dev_err(dev, "failed to get SCPI payload mem resource\n");
> +                       ret = -EINVAL;
> +                       goto err;
> +               }
> +
> +               size = resource_size(&res);
> +               pchan->rx_payload = devm_ioremap(dev, res.start, size);
> +               if (!pchan->rx_payload) {
> +                       dev_err(dev, "failed to ioremap SCPI payload\n");
> +                       ret = -EADDRNOTAVAIL;
> +                       goto err;
> +               }
> +               pchan->tx_payload = pchan->rx_payload + (size >> 1);
> +
> +               cl->dev = dev;
> +               cl->rx_callback = scpi_handle_remote_msg;
> +               cl->tx_prepare = scpi_tx_prepare;
> +               cl->tx_block = true;
> +               cl->tx_tout = 50;
> +               cl->knows_txdone = false; /* controller can ack */
>
 This is the cause of your problems that you think should be solved by
using hrtimer.

 Controller may or may not (like MHU) set txdone_irq. However every
scpi command (struct scpi_ops members) is replied to as a response
packet reporting success or failure.
So the client should set 'knows_txdone' to be true unless it is told
the controller on that platform supports txdone_irq (what you call
'ack').

-Jassi
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