linux-kernel - Re: [PATCH V5 05/12] mailbox: Add NVIDIA Tegra XUSB mailbox driver

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Date:	Mon, 24 Nov 2014 09:20:07 -0800
From:	Andrew Bresticker <abrestic@...omium.org>
To:	Jassi Brar <jaswinder.singh@...aro.org>
Cc:	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Alexandre Courbot <gnurou@...il.com>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	Mark Rutland <mark.rutland@....com>,
	Devicetree List <devicetree@...r.kernel.org>,
	Linux USB list <linux-usb@...r.kernel.org>,
	Russell King <linux@....linux.org.uk>,
	Mathias Nyman <mathias.nyman@...el.com>,
	Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Jassi Brar <jassisinghbrar@...il.com>,
	lkml <linux-kernel@...r.kernel.org>,
	Kishon Vijay Abraham I <kishon@...com>,
	Olof Johansson <olof@...om.net>,
	Rob Herring <robh+dt@...nel.org>,
	Alan Stern <stern@...land.harvard.edu>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Kumar Gala <galak@...eaurora.org>,
	Grant Likely <grant.likely@...aro.org>,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH V5 05/12] mailbox: Add NVIDIA Tegra XUSB mailbox driver

On Mon, Nov 24, 2014 at 12:34 AM, Jassi Brar <jaswinder.singh@...aro.org> wrote:
> On 18 November 2014 at 04:11, Andrew Bresticker <abrestic@...omium.org> wrote:
>
>> +
>> +static int tegra_xusb_mbox_send_data(struct mbox_chan *chan, void *data)
>> +{
>> +       struct tegra_xusb_mbox *mbox = to_tegra_mbox(chan->mbox);
>> +       struct tegra_xusb_mbox_msg *msg = data;
>> +       unsigned long flags;
>> +       u32 reg, owner;
>> +
>> +       dev_dbg(mbox->mbox.dev, "TX message %#x:%#x\n", msg->cmd, msg->data);
>> +
>> +       /* ACK/NAK must be sent with the controller as the mailbox owner */
>> +       if (msg->cmd == MBOX_CMD_ACK || msg->cmd == MBOX_CMD_NAK)
>> +               owner = MBOX_OWNER_FW;
>> +       else
>> +               owner = MBOX_OWNER_SW;
>> +
>> +       spin_lock_irqsave(&mbox->lock, flags);
>> +
>> +       /* Acquire mailbox */
>> +       if (mbox_readl(mbox, XUSB_CFG_ARU_MBOX_OWNER) != MBOX_OWNER_NONE) {
>> +               dev_err(mbox->mbox.dev, "Mailbox not idle\n");
>> +               goto busy;
>> +       }
>> +       mbox_writel(mbox, owner, XUSB_CFG_ARU_MBOX_OWNER);
>> +       if (mbox_readl(mbox, XUSB_CFG_ARU_MBOX_OWNER) != owner) {
>> +               dev_err(mbox->mbox.dev, "Failed to acquire mailbox");
>> +               goto busy;
>> +       }
>> +
>> +       mbox_writel(mbox, mbox_pack_msg(msg), XUSB_CFG_ARU_MBOX_DATA_IN);
>> +       reg = mbox_readl(mbox, XUSB_CFG_ARU_MBOX_CMD);
>> +       reg |= MBOX_INT_EN | MBOX_DEST_FALC;
>> +       mbox_writel(mbox, reg, XUSB_CFG_ARU_MBOX_CMD);
>> +
>> +       spin_unlock_irqrestore(&mbox->lock, flags);
>> +
>> +       return 0;
>> +busy:
>> +       spin_unlock_irqrestore(&mbox->lock, flags);
>> +       return -EBUSY;
>> +}
>> +
>> +static int tegra_xusb_mbox_startup(struct mbox_chan *chan)
>> +{
>> +       return 0;
>> +}
>> +
>> +static void tegra_xusb_mbox_shutdown(struct mbox_chan *chan)
>> +{
>> +}
>> +
>> +static bool tegra_xusb_mbox_last_tx_done(struct mbox_chan *chan)
>> +{
>> +       /*
>> +        * Transmissions are assumed to be completed as soon as they are
>> +        * written to the mailbox.
>> +        */
>> +       return true;
>>
> In .send_data() you you mark the channel busy by setting the
> XUSB_CFG_ARU_MBOX_OWNER to !MBOX_OWNER_NONE, which remains so until
> you get an IRQ. So maybe you should check for the OWNER_NONE flag in
> .last_tx_done()?

Ah, you're right.  It does look like the controller firmware clears MBOX_OWNER.
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