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Date: Mon, 2 Feb 2015 15:14:16 +0800
From: Ley Foon Tan <lftan@...era.com>
To: Jassi Brar <jassisinghbrar@...il.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
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, Feb 2, 2015 at 3:04 PM, Jassi Brar <jassisinghbrar@...il.com> wrote:
> 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?
Currently MBOX_POLLING_MS is used for RX polling and TX polling.
I think change to 5ms should be fine, 50ms is a bit too long. Do you
okay with this?
>
>> +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
Noted.
>
>> +
>> +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?
Yes, can change to polling mode.
>
>> + }
>> + 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;
>> +}
>> +
>
Regards
Ley Foon
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