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Message-ID: <CAHuqX+Et68WGWET36nsBJPvtr2m3f5s+qmq-mA72YkcQdp1tcQ@mail.gmail.com>
Date: Fri, 7 Dec 2012 20:36:58 +0900
From: Giridhar Maruthy <giridhar.maruthy@...aro.org>
To: Subash Patel <subashrp@...il.com>
Cc: ben-linux@...ff.org, kgene.kim@...sung.com, khali@...ux-fr.org,
w.sang@...gutronix.de, linux-arm-kernel@...ts.infradead.org,
linux-samsung-soc@...r.kernel.org, linux-i2c@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] I2C: EXYNOS: Add slave support to i2c
Thanks for the review Subash. Please find my reply below.
On 6 December 2012 23:05, Subash Patel <subashrp@...il.com> wrote:
> Hi Giridhar,
>
>
> On 12/03/2012 05:46 PM, Giridhar Maruthy wrote:
>>
>> This patch adds slave support to i2c. The dt entry i2c-mode
>> decides at probe time if the controller needs to work in
>> slave mode and the controller is accordingly programmed.
>>
>> Signed-off-by: Giridhar Maruthy <giridhar.maruthy@...aro.org
>> <mailto:giridhar.maruthy@...aro.org>>
>>
>> ---
>> drivers/i2c/busses/i2c-s3c2410.c | 100
>> ++++++++++++++++++++++++++------------
>> 1 file changed, 68 insertions(+), 32 deletions(-)
>>
>> diff --git a/drivers/i2c/busses/i2c-s3c2410.c
>> b/drivers/i2c/busses/i2c-s3c2410.c
>> index e93e7d6..d83a6d7 100644
>> --- a/drivers/i2c/busses/i2c-s3c2410.c
>> +++ b/drivers/i2c/busses/i2c-s3c2410.c
>> @@ -53,6 +53,9 @@
>> /* Max time to wait for bus to become idle after a xfer (in us) */
>> #define S3C2410_IDLE_TIMEOUT 5000
>>
>> +/* To find the master/slave mode of current controller */
>> +#define is_master(i2c) (!i2c->i2c_mode)
>> +
>> /* i2c controller state */
>> enum s3c24xx_i2c_state {
>> STATE_IDLE,
>> @@ -89,6 +92,8 @@ struct s3c24xx_i2c {
>> #ifdef CONFIG_CPU_FREQ
>> struct notifier_block freq_transition;
>> #endif
>> + /* i2c_mode: 0 is for master; and 1 is for slave */
>> + unsigned int i2c_mode;
>> };
>>
>> static struct platform_device_id s3c24xx_driver_ids[] = {
>> @@ -202,11 +207,21 @@ static void s3c24xx_i2c_message_start(struct
>> s3c24xx_i2c *i2c,
>> stat = 0;
>> stat |= S3C2410_IICSTAT_TXRXEN;
>>
>> - if (msg->flags & I2C_M_RD) {
>> - stat |= S3C2410_IICSTAT_MASTER_RX;
>> - addr |= 1;
>> - } else
>> - stat |= S3C2410_IICSTAT_MASTER_TX;
>> + if (is_master(i2c)) {
>> + /* Master mode */
>> + if (msg->flags & I2C_M_RD) {
>> + stat |= S3C2410_IICSTAT_MASTER_RX;
>> + addr |= 1;
>> + } else
>> + stat |= S3C2410_IICSTAT_MASTER_TX;
>> + } else {
>> + /* Slave mode */
>> + if (msg->flags & I2C_M_RD) {
>> + stat |= S3C2410_IICSTAT_SLAVE_RX;
>> + addr |= 1;
>> + } else
>> + stat |= S3C2410_IICSTAT_SLAVE_TX;
>> + }
>>
>> if (msg->flags & I2C_M_REV_DIR_ADDR)
>> addr ^= 1;
>> @@ -228,8 +243,10 @@ static void s3c24xx_i2c_message_start(struct
>> s3c24xx_i2c *i2c,
>> dev_dbg(i2c->dev, "iiccon, %08lx\n", iiccon);
>> writel(iiccon, i2c->regs + S3C2410_IICCON);
>>
>> - stat |= S3C2410_IICSTAT_START;
>> - writel(stat, i2c->regs + S3C2410_IICSTAT);
>> + if (is_master(i2c)) {
>> + stat |= S3C2410_IICSTAT_START;
>> + writel(stat, i2c->regs + S3C2410_IICSTAT);
>> + }
>> }
>>
>> static inline void s3c24xx_i2c_stop(struct s3c24xx_i2c *i2c, int ret)
>> @@ -272,14 +289,19 @@ static inline void s3c24xx_i2c_stop(struct
>> s3c24xx_i2c *i2c, int ret)
>> * devices, the host as Master and the HDMIPHY device as the
>> slave.
>> * Skipping the STOP condition has been tested on this bus and
>> works.
>> */
>> - if (i2c->quirks & QUIRK_HDMIPHY) {
>> - /* Stop driving the I2C pins */
>> - iicstat &= ~S3C2410_IICSTAT_TXRXEN;
>> - } else {
>> - /* stop the transfer */
>> - iicstat &= ~S3C2410_IICSTAT_START;
>> + if (is_master(i2c)) {
>> + if (i2c->quirks & QUIRK_HDMIPHY) {
>> + /* Stop driving the I2C pins */
>> + iicstat &= ~S3C2410_IICSTAT_TXRXEN;
>> + } else {
>> + /* stop the transfer */
>> + if (is_master(i2c)) {
>> + /* Start/Stop required only for master */
>> + iicstat &= ~S3C2410_IICSTAT_START;
>> + }
>> + }
>> + writel(iicstat, i2c->regs + S3C2410_IICSTAT);
>
>
> I don't see i2c controller for HDMIPHY working in slave mode. So do we need
> to check if its master and proceed? Cant the quirks check enough for it?
> Even if it is configured as slave, there is no error indication for this
> here.
My understanding is that the HDMIPHY always commands and hence,
HDMIPHY does not need to be slave at all.
But if you think it is a policy decision which need not be implemented
in driver, I agree with you.
>
>> }
>> - writel(iicstat, i2c->regs + S3C2410_IICSTAT);
>>
>> i2c->state = STATE_STOP;
>>
>> @@ -348,7 +370,8 @@ static int i2c_s3c_irq_nextbyte(struct s3c24xx_i2c
>> *i2c, unsigned long iicstat)
>> */
>>
>> if (iicstat & S3C2410_IICSTAT_LASTBIT &&
>> - !(i2c->msg->flags & I2C_M_IGNORE_NAK)) {
>> + !(i2c->msg->flags & I2C_M_IGNORE_NAK) &&
>> + is_master(i2c)) {
>> /* ack was not received... */
>>
>> dev_dbg(i2c->dev, "ack was not received\n");
>> @@ -380,7 +403,7 @@ static int i2c_s3c_irq_nextbyte(struct s3c24xx_i2c
>> *i2c, unsigned long iicstat)
>> * end of the message, and if so, work out what to do
>> */
>>
>> - if (!(i2c->msg->flags & I2C_M_IGNORE_NAK)) {
>> + if (!(i2c->msg->flags & I2C_M_IGNORE_NAK) &&
>> is_master(i2c)) {
>> if (iicstat & S3C2410_IICSTAT_LASTBIT) {
>> dev_dbg(i2c->dev, "WRITE: No Ack\n");
>>
>> @@ -432,7 +455,6 @@ static int i2c_s3c_irq_nextbyte(struct s3c24xx_i2c
>> *i2c, unsigned long iicstat)
>>
>> } else {
>> /* send stop */
>> -
>> s3c24xx_i2c_stop(i2c, 0);
>> }
>> break;
>> @@ -447,7 +469,7 @@ static int i2c_s3c_irq_nextbyte(struct s3c24xx_i2c
>> *i2c, unsigned long iicstat)
>> i2c->msg->buf[i2c->msg_ptr++] = byte;
>>
>> prepare_read:
>> - if (is_msglast(i2c)) {
>> + if (is_msglast(i2c) && is_master(i2c)) {
>> /* last byte of buffer */
>>
>> if (is_lastmsg(i2c))
>> @@ -612,11 +634,13 @@ static int s3c24xx_i2c_doxfer(struct s3c24xx_i2c
>> *i2c,
>> if (i2c->suspended)
>> return -EIO;
>>
>> - ret = s3c24xx_i2c_set_master(i2c);
>> - if (ret != 0) {
>> - dev_err(i2c->dev, "cannot get bus (error %d)\n", ret);
>> - ret = -EAGAIN;
>> - goto out;
>> + if (is_master(i2c)) {
>> + ret = s3c24xx_i2c_set_master(i2c);
>> + if (ret != 0) {
>> + dev_err(i2c->dev, "cannot get bus (error %d)\n",
>> ret);
>> + ret = -EAGAIN;
>> + goto out;
>> + }
>> }
>>
>> i2c->msg = msgs;
>> @@ -628,23 +652,29 @@ static int s3c24xx_i2c_doxfer(struct s3c24xx_i2c
>> *i2c,
>> s3c24xx_i2c_enable_irq(i2c);
>> s3c24xx_i2c_message_start(i2c, msgs);
>>
>> - timeout = wait_event_timeout(i2c->wait, i2c->msg_num == 0, HZ *
>> 5);
>> + if (is_master(i2c))
>> + timeout = wait_event_timeout(i2c->wait,\
>> + i2c->msg_num == 0, HZ * 5);
>> + else
>> + wait_event_interruptible(i2c->wait, i2c->msg_num == 0);
>>
>> ret = i2c->msg_idx;
>>
>> /* having these next two as dev_err() makes life very
>> * noisy when doing an i2cdetect */
>>
>> - if (timeout == 0)
>> - dev_dbg(i2c->dev, "timeout\n");
>> - else if (ret != num)
>> - dev_dbg(i2c->dev, "incomplete xfer (%d)\n", ret);
>> + if (is_master(i2c)) {
>> + if (timeout == 0)
>> + dev_dbg(i2c->dev, "timeout\n");
>> + else if (ret != num)
>> + dev_dbg(i2c->dev, "incomplete xfer (%d)\n", ret);
>>
>> - /* For QUIRK_HDMIPHY, bus is already disabled */
>> - if (i2c->quirks & QUIRK_HDMIPHY)
>> - goto out;
>> + /* For QUIRK_HDMIPHY, bus is already disabled */
>> + if (i2c->quirks & QUIRK_HDMIPHY)
>> + goto out;
>>
>> - s3c24xx_i2c_wait_idle(i2c);
>> + s3c24xx_i2c_wait_idle(i2c);
>> + }
>>
>> out:
>> return ret;
>> @@ -963,6 +993,7 @@ s3c24xx_i2c_parse_dt(struct device_node *np, struct
>> s3c24xx_i2c *i2c)
>> of_property_read_u32(np, "samsung,i2c-slave-addr",
>> &pdata->slave_addr);
>> of_property_read_u32(np, "samsung,i2c-max-bus-freq",
>> (u32 *)&pdata->frequency);
>> + of_property_read_u32(np, "samsung,i2c-mode", &i2c->i2c_mode);
>> }
>> #else
>> static void
>> @@ -1004,6 +1035,10 @@ static int s3c24xx_i2c_probe(struct
>> platform_device *pdev)
>> goto err_noclk;
>> }
>>
>> + /* By default, i2c works in master mode */
>> + /* This currently will be updated using DT */
>> + i2c->i2c_mode = 0;
>> +
>> i2c->quirks = s3c24xx_get_device_quirks(pdev);
>> if (pdata)
>> memcpy(i2c->pdata, pdata, sizeof(*pdata));
>> @@ -1017,6 +1052,7 @@ static int s3c24xx_i2c_probe(struct
>> platform_device *pdev)
>> i2c->adap.class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
>> i2c->tx_setup = 50;
>>
>> +
>> init_waitqueue_head(&i2c->wait);
>>
>> /* find the clock and enable it */
>> --
>> 1.7.9.5
>>
>>
>>
>>
>> _______________________________________________
>> linux-arm-kernel mailing list
>> linux-arm-kernel@...ts.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>>
> Regards,
> Subash
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