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Date: Mon, 2 Feb 2015 12:34:29 +0530
From: Jassi Brar <jassisinghbrar@...il.com>
To: Ley Foon Tan <lftan@...era.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Ley Foon Tan <lftan.linux@...il.com>,
Suman Anna <s-anna@...com>, devicetree@...r.kernel.org,
Dinh Nguyen <dinh.linux@...il.com>
Subject: Re: [PATCH v2] mailbox: Add Altera mailbox driver
On Mon, Dec 22, 2014 at 3:14 PM, Ley Foon Tan <lftan@...era.com> wrote:
...
> diff --git a/drivers/mailbox/mailbox-altera.c b/drivers/mailbox/mailbox-altera.c
> new file mode 100644
> index 0000000..8019795
> --- /dev/null
> +++ b/drivers/mailbox/mailbox-altera.c
> @@ -0,0 +1,385 @@
> +/*
> + * Copyright Altera Corporation (C) 2013-2014. All rights reserved
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along with
> + * this program. If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/mailbox_controller.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +
> +#define DRIVER_NAME "altera-mailbox"
> +
> +#define MAILBOX_CMD_REG 0x00
> +#define MAILBOX_PTR_REG 0x04
> +#define MAILBOX_STS_REG 0x08
> +#define MAILBOX_INTMASK_REG 0x0C
> +
> +#define INT_PENDING_MSK 0x1
> +#define INT_SPACE_MSK 0x2
> +
> +#define STS_PENDING_MSK 0x1
> +#define STS_FULL_MSK 0x2
> +#define STS_FULL_OFT 0x1
> +
> +#define MBOX_PENDING(status) (((status) & STS_PENDING_MSK))
> +#define MBOX_FULL(status) (((status) & STS_FULL_MSK) >> STS_FULL_OFT)
> +
> +enum altera_mbox_msg {
> + MBOX_CMD = 0,
> + MBOX_PTR,
> +};
> +
> +#define MBOX_POLLING_MS 1 /* polling interval 1ms */
> +
The intention is too aggressive - though poll won't be before next jiffy (>1ms).
And if you are not expecting a reply, it should be even bigger. Say,
50ms default and 5ms when you expect RX?
> +struct altera_mbox {
> + bool is_sender; /* 1-sender, 0-receiver */
> + bool intr_mode;
> + int irq;
> + void __iomem *mbox_base;
> + struct device *dev;
> + struct mbox_controller controller;
> +
> + /* If the controller supports only RX polling mode */
> + struct timer_list rxpoll_timer;
> +};
> +
> +static struct altera_mbox *mbox_chan_to_altera_mbox(struct mbox_chan *chan)
> +{
> + if (!chan || !chan->con_priv)
> + return NULL;
> +
> + return (struct altera_mbox *)chan->con_priv;
> +}
> +
> +static inline int altera_mbox_full(struct altera_mbox *mbox)
> +{
> + u32 status;
> +
> + status = readl(mbox->mbox_base + MAILBOX_STS_REG);
> + return MBOX_FULL(status);
> +}
>
s/readl/readl_relaxed and s/writel/writel_relaxed everywhere
> +
> +static inline int altera_mbox_pending(struct altera_mbox *mbox)
> +{
> + u32 status;
> +
> + status = readl(mbox->mbox_base + MAILBOX_STS_REG);
> + return MBOX_PENDING(status);
> +}
> +
> +static void altera_mbox_rx_intmask(struct altera_mbox *mbox, bool enable)
> +{
> + u32 mask;
> +
> + mask = readl(mbox->mbox_base + MAILBOX_INTMASK_REG);
> + if (enable)
> + mask |= INT_PENDING_MSK;
> + else
> + mask &= ~INT_PENDING_MSK;
> + writel(mask, mbox->mbox_base + MAILBOX_INTMASK_REG);
> +}
> +
> +static void altera_mbox_tx_intmask(struct altera_mbox *mbox, bool enable)
> +{
> + u32 mask;
> +
> + mask = readl(mbox->mbox_base + MAILBOX_INTMASK_REG);
> + if (enable)
> + mask |= INT_SPACE_MSK;
> + else
> + mask &= ~INT_SPACE_MSK;
> + writel(mask, mbox->mbox_base + MAILBOX_INTMASK_REG);
> +}
> +
> +static bool altera_mbox_is_sender(struct altera_mbox *mbox)
> +{
> + u32 reg;
> + /* Write a magic number to PTR register and read back this register.
> + * This register is read-write if it is a sender.
> + */
> + #define MBOX_MAGIC 0xA5A5AA55
> + writel(MBOX_MAGIC, mbox->mbox_base + MAILBOX_PTR_REG);
> + reg = readl(mbox->mbox_base + MAILBOX_PTR_REG);
> + if (reg == MBOX_MAGIC) {
> + /* Clear to 0 */
> + writel(0, mbox->mbox_base + MAILBOX_PTR_REG);
> + return true;
> + }
> + return false;
> +}
> +
> +static void altera_mbox_rx_data(struct mbox_chan *chan)
> +{
> + struct altera_mbox *mbox = mbox_chan_to_altera_mbox(chan);
> + u32 data[2];
> +
> + if (altera_mbox_pending(mbox)) {
> + data[MBOX_PTR] = readl(mbox->mbox_base + MAILBOX_PTR_REG);
> + data[MBOX_CMD] = readl(mbox->mbox_base + MAILBOX_CMD_REG);
> + mbox_chan_received_data(chan, (void *)data);
> + }
> +}
> +
> +static void altera_mbox_poll_rx(unsigned long data)
> +{
> + struct mbox_chan *chan = (struct mbox_chan *)data;
> + struct altera_mbox *mbox = mbox_chan_to_altera_mbox(chan);
> +
> + altera_mbox_rx_data(chan);
> +
> + mod_timer(&mbox->rxpoll_timer,
> + jiffies + msecs_to_jiffies(MBOX_POLLING_MS));
> +}
> +
> +static irqreturn_t altera_mbox_tx_interrupt(int irq, void *p)
> +{
> + struct mbox_chan *chan = (struct mbox_chan *)p;
> + struct altera_mbox *mbox = mbox_chan_to_altera_mbox(chan);
> +
> + altera_mbox_tx_intmask(mbox, false);
> + mbox_chan_txdone(chan, 0);
> +
> + return IRQ_HANDLED;
> +}
> +
> +static irqreturn_t altera_mbox_rx_interrupt(int irq, void *p)
> +{
> + struct mbox_chan *chan = (struct mbox_chan *)p;
> +
> + altera_mbox_rx_data(chan);
> + return IRQ_HANDLED;
> +}
> +
> +static int altera_mbox_startup_sender(struct mbox_chan *chan)
> +{
> + int ret;
> + struct altera_mbox *mbox = mbox_chan_to_altera_mbox(chan);
> +
> + if (mbox->intr_mode) {
> + ret = request_irq(mbox->irq, altera_mbox_tx_interrupt, 0,
> + DRIVER_NAME, chan);
> + if (unlikely(ret)) {
> + dev_err(mbox->dev,
> + "failed to register mailbox interrupt:%d\n",
> + ret);
> + return ret;
> + }
> + }
> +
> + return 0;
> +}
> +
> +static int altera_mbox_startup_receiver(struct mbox_chan *chan)
> +{
> + int ret;
> + struct altera_mbox *mbox = mbox_chan_to_altera_mbox(chan);
> +
> + if (mbox->intr_mode) {
> + ret = request_irq(mbox->irq, altera_mbox_rx_interrupt, 0,
> + DRIVER_NAME, chan);
> + if (unlikely(ret)) {
> + dev_err(mbox->dev,
> + "failed to register mailbox interrupt:%d\n",
> + ret);
> + return ret;
>
Is this really fatal? Maybe continue using the timer scheme below?
> + }
> + altera_mbox_rx_intmask(mbox, true);
> + } else {
> + /* Setup polling timer */
> + setup_timer(&mbox->rxpoll_timer, altera_mbox_poll_rx,
> + (unsigned long)chan);
> + mod_timer(&mbox->rxpoll_timer,
> + jiffies + msecs_to_jiffies(MBOX_POLLING_MS));
> + }
> +
> + return 0;
> +}
> +
Just these minor comments.
-Jassi
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