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

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Message-ID: <55B89100.3020802@arm.com>
Date:	Wed, 29 Jul 2015 09:38:24 +0100
From:	Sudeep Holla <sudeep.holla@....com>
To:	Jassi Brar <jassisinghbrar@...il.com>
CC:	Sudeep Holla <sudeep.holla@....com>,
	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 29/07/15 09:05, Jassi Brar wrote:
> 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.
>

Ah sorry, it's stupid mistake on my part while writing the comment. It
should have been controller can't ack, fixed locally now thanks for
pointing it out.

>   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.

No that's not true, I have already mentioned that couple of times in the
other thread. It's just wrong comment here which went unnoticed from
day#1, sorry for that.

> 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').
>

I got the concept but SCP can't ack via protocol, protocol has no such
provision and it sets flags in MHU status register.

Regards,
Sudeep
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