[U-Boot] [EXT] Re: [PATCH] i2c: pcf2127: fix bug that read wrong time

Chuanhua Han
2019-05-22T09:31:35Z

> -----Original Message-----
> From: Lukasz Majewski <lukma@denx.de>
> Sent: 2019年5月22日 16:41
> To: Chuanhua Han <chuanhua.han@nxp.com>
> Cc: hs at denx.de; u-boot at lists.denx.de; Biwen Li <biwen.li@nxp.com>;
> sjg at chromium.org; Stefano Babic <sbabic@denx.de>
> Subject: Re: [EXT] Re: [PATCH] i2c: pcf2127: fix bug that read wrong time
>
> Hi Chuanhua,
>
> > > -----Original Message-----
> > > From: Lukasz Majewski <lukma@denx.de>
> > > Sent: 2019年5月22日 15:16
> > > To: Chuanhua Han <chuanhua.han@nxp.com>
> > > Cc: hs at denx.de; u-boot at lists.denx.de; Biwen Li <biwen.li@nxp.com>;
> > > sjg at chromium.org
> > > Subject: [EXT] Re: [PATCH] i2c: pcf2127: fix bug that read wrong
> > > time
> > >
> > > Hi Chuanhua,
> > >
> > > > Because i2c driver does not generate a stop bit when reading
> > > > registers of pcf2127
> > >
> > > The change (in the common i2c code) is rather large when considering
> > > the description above.
> > >
> > > Could you write a more detailed patch description? Is this only the
> > > problem with i2c in DM?
> > OK, This is a problem with the i2c transport framework. After writing
> > the register address that you want to read, the stop signal is missing
> > before reading the register data.
> > >
> > > Is the same code (as introduced in this commit) available in Linux
> > > kernel?
> > The kernel does not have such a problem
>
> Do you know maybe why such issue is not present on Linux kernel?
The kernel code is encapsulated when reading the pcf2127 register, which separates the read and write,
thus generating a stop signal before reading the register.
Eg: Here is the wrapper made by the kernel code:
static int pcf2127_i2c_read(void *context, const void *reg, size_t reg_size,
void *val, size_t val_size)
{
struct device *dev = context;
struct i2c_client *client = to_i2c_client(dev);
int ret;

if (WARN_ON(reg_size != 1))
return -EINVAL;

ret = i2c_master_send(client, reg, 1);
if (ret != 1)
return ret < 0 ? ret : -EIO;

ret = i2c_master_recv(client, val, val_size);
if (ret != val_size)
return ret < 0 ? ret : -EIO;

return 0;
}
>
> > > How the error is reproduced? What are the symptoms of it?
> > You can use the i2c command to read the register data of pcf2127.
>
> So the problem is with using "i2c ..." commands from U-Boot prompt?
Yes,but adding debugging to the rtc driver is also the same problem
>
> > You will find that you want to read the address 0 of the register,
> > but the data of the 1 address is read, and the data read later will
> > be offset.
>
> As fair as I can tell the pcf2127 has its own DM aware driver at
> driver/rtc/pcf2127.c.
>
> Is this driver broken so you need to modify the generic i.MX I2C code?
> Have you tried to test this driver on your setup?
Pcf2127 driver also has problems, has been modified, need i2c general code to support
>
> > >
> > > In which way the pcf2127 needs special treatment (non I2C
> > > compatible)? How does it differ from other RTC devices?
> > According to the pcf2127 chip manual, when you need to read the
> > internal register data, you need to write the register address first
> > and then need stop bit(it is necessary).
> > >
> > > >
> > > > Signed-off-by: Biwen Li <biwen.li@nxp.com>
> > > > Signed-off-by: Chuanhua Han <chuanhua.han@nxp.com>
> > > > ---
> > > > drivers/i2c/i2c-uclass.c | 2 ++
> > > > drivers/i2c/mxc_i2c.c | 70
> > > > +++++++++++++++++++++++++++++++++++----- drivers/rtc/pcf2127.c
> > > > | 18 ++++++----- include/i2c.h | 2 ++
> > > > 4 files changed, 76 insertions(+), 16 deletions(-)
> > > >
> > > > diff --git a/drivers/i2c/i2c-uclass.c b/drivers/i2c/i2c-uclass.c
> > > > index e47abf1833..18f7364d72 100644
> > > > --- a/drivers/i2c/i2c-uclass.c
> > > > +++ b/drivers/i2c/i2c-uclass.c
> > > > @@ -141,6 +141,8 @@ int dm_i2c_read(struct udevice *dev, uint
> > > > offset, uint8_t *buffer, int len) if (len) {
> > > > ptr->addr = chip->chip_addr;
> > > > ptr->flags = chip->flags & DM_I2C_CHIP_10BIT ?
> > > > I2C_M_TEN : 0;
> > > > + ptr->flags |= chip->flags &
> > > > DM_I2C_CHIP_RD_NEED_STOP_BIT ?
> > > > + I2C_M_RD_NEED_STOP_BIT : 0;
> > > > ptr->flags |= I2C_M_RD;
> > > > ptr->len = len;
> > > > ptr->buf = buffer;
> > > > diff --git a/drivers/i2c/mxc_i2c.c b/drivers/i2c/mxc_i2c.c index
> > > > 73b9807598..241367bac8 100644
> > > > --- a/drivers/i2c/mxc_i2c.c
> > > > +++ b/drivers/i2c/mxc_i2c.c
> > > > @@ -962,6 +962,8 @@ static int mxc_i2c_xfer(struct udevice *bus,
> > > > struct i2c_msg *msg, int nmsgs) int reg_shift =
> > > > i2c_bus->driver_data & I2C_QUIRK_FLAG ? VF610_I2C_REGSHIFT :
> > > > IMX_I2C_REGSHIFT; int read_mode;
> > > > + bool quirk = i2c_bus->driver_data & I2C_QUIRK_FLAG ?
> > > > true : false;
> > > > + unsigned int temp;
> > > >
> > > > /* Here address len is set to -1 to not send any address
> > > > at first.
> > > > * Otherwise i2c_init_transfer will send the chip
> > > > address with write @@ -976,6 +978,7 @@ static int
> > > > mxc_i2c_xfer(struct udevice *bus, struct i2c_msg *msg, int nmsgs)
> > > > read_mode = -1; /* So it's always different on the first message
> > > > */ for (; nmsgs > 0; nmsgs--, msg++) { const int msg_is_read
> > > > = !!(msg->flags & I2C_M_RD);
> > > > + bool next_is_read = nmsgs > 1 && (msg[1].flags &
> > > > I2C_M_RD);
> > > > debug("i2c_xfer: chip=0x%x, len=0x%x, dir=%c\n",
> > > > msg->addr, msg->len, msg_is_read ? 'R' : 'W');
> > > > @@ -983,13 +986,16 @@ static int mxc_i2c_xfer(struct udevice *bus,
> > > > struct i2c_msg *msg, int nmsgs) if (msg_is_read != read_mode) {
> > > > /* Send repeated start if not 1st
> > > > message */ if (read_mode != -1) {
> > > > - debug("i2c_xfer: [RSTART]\n");
> > > > - ret = readb(base + (I2CR <<
> > > > reg_shift));
> > > > - ret |= I2CR_RSTA;
> > > > - writeb(ret, base + (I2CR <<
> > > > reg_shift));
> > > > + if (!(msg[1].flags &
> > > > I2C_M_RD_NEED_STOP_BIT)) {
> > > > + debug("i2c_xfer:
> > > > [RSTART]\n");
> > > > + ret = readb(base + (I2CR
> > > > << reg_shift));
> > > > + ret |= I2CR_RSTA;
> > > > + writeb(ret, base + (I2CR
> > > > << reg_shift));
> > > > + }
> > > > }
> > > > debug("i2c_xfer: [ADDR %02x | %c]\n",
> > > > msg->addr, msg_is_read ? 'R' : 'W');
> > > > +
> > > > ret = tx_byte(i2c_bus, (msg->addr << 1)
> > > > | msg_is_read); if (ret < 0) {
> > > > debug("i2c_xfer: [STOP]\n");
> > > > @@ -999,16 +1005,64 @@ static int mxc_i2c_xfer(struct udevice
> > > > *bus, struct i2c_msg *msg, int nmsgs) read_mode = msg_is_read;
> > > > }
> > > >
> > > > - if (msg->flags & I2C_M_RD)
> > > > + if (msg->flags & I2C_M_RD) {
> > > > ret = i2c_read_data(i2c_bus, msg->addr,
> > > > msg->buf, msg->len, nmsgs == 1 ||
> > > > (msg->flags
> > > > & I2C_M_STOP));
> > > > - else
> > > > - ret = i2c_write_data(i2c_bus, msg->addr,
> > > > msg->buf,
> > > > - msg->len);
> > > > + if (ret < 0)
> > > > + break;
> > > > + continue;
> > > > + }
> > > >
> > > > + /* Write message */
> > > > + ret = i2c_write_data(i2c_bus, msg->addr,
> > > > msg->buf,
> > > > + msg->len);
> > > > if (ret < 0)
> > > > break;
> > > > +
> > > > + if (!next_is_read)
> > > > + continue;
> > > > +
> > > > + /* Read message following write message */
> > > > + if (msg[1].flags & I2C_M_RD_NEED_STOP_BIT) {
> > > > + /* Generate a stop bit */
> > > > + i2c_imx_stop(i2c_bus);
> > > > + /* Reset i2c slave */
> > > > + i2c_force_reset_slave();
> > > > +
> > > > + /* Enable I2C controller */
> > > > + if (quirk)
> > > > + ret = readb(base + (I2CR <<
> > > > reg_shift))
> > > > + & I2CR_IDIS;
> > > > + else
> > > > + ret = !(readb(base + (I2CR <<
> > > > reg_shift))
> > > > + & I2CR_IEN);
> > > > + if (ret) {
> > > > + writeb(I2CR_IEN, base + (I2CR <<
> > > > reg_shift));
> > > > + /* Wait for controller to be
> > > > stable */
> > > > + udelay(50);
> > > > + }
> > > > +
> > > > + /* Clear interrupt bit */
> > > > + writeb(I2SR_IIF_CLEAR, base + (I2SR <<
> > > > reg_shift));
> > > > + ret = wait_for_sr_state(i2c_bus,
> > > > ST_BUS_IDLE);
> > > > + if (ret < 0)
> > > > + return ret;
> > > > +
> > > > + /* Start I2C transaction */
> > > > + temp = readb(base + (I2CR << reg_shift));
> > > > + temp |= I2CR_MSTA;
> > > > + writeb(temp, base + (I2CR << reg_shift));
> > > > +
> > > > + ret = wait_for_sr_state(i2c_bus,
> > > > ST_BUS_BUSY);
> > > > + if (ret < 0)
> > > > + return ret;
> > > > +
> > > > + /* Enter transfer mode */
> > > > + temp |= I2CR_MTX | I2CR_TX_NO_AK;
> > > > + writeb(temp, base + (I2CR << reg_shift));
> > > > + udelay(50);
> > > > + }
> > > > }
> > > >
> > > > if (ret)
> > > > diff --git a/drivers/rtc/pcf2127.c b/drivers/rtc/pcf2127.c index
> > > > dcf0340b4d..010c45ecbf 100644
> > > > --- a/drivers/rtc/pcf2127.c
> > > > +++ b/drivers/rtc/pcf2127.c
> > > > @@ -24,12 +24,9 @@
> > > >
> > > > static int pcf2127_rtc_set(struct udevice *dev, const struct
> > > > rtc_time *tm) {
> > > > - uchar buf[8];
> > > > + uchar buf[7] = {0};
> > > > int i = 0, ret;
> > > >
> > > > - /* start register address */
> > > > - buf[i++] = PCF2127_REG_SC;
> > > > -
> > > > /* hours, minutes and seconds */
> > > > buf[i++] = bin2bcd(tm->tm_sec);
> > > > buf[i++] = bin2bcd(tm->tm_min);
> > > > @@ -44,7 +41,7 @@ static int pcf2127_rtc_set(struct udevice *dev,
> > > > const struct rtc_time *tm) buf[i++] = bin2bcd(tm->tm_year % 100);
> > > >
> > > > /* write register's data */
> > > > - ret = dm_i2c_write(dev, PCF2127_REG_CTRL1, buf,
> > > > sizeof(buf));
> > > > + ret = dm_i2c_write(dev, PCF2127_REG_SC, buf, i);
> > > >
> > > > return ret;
> > > > }
> > > > @@ -54,9 +51,6 @@ static int pcf2127_rtc_get(struct udevice *dev,
> > > > struct rtc_time *tm) int ret = 0;
> > > > uchar buf[10] = { PCF2127_REG_CTRL1 };
> > > >
> > > > - ret = dm_i2c_write(dev, PCF2127_REG_CTRL1, buf, 1);
> > > > - if (ret < 0)
> > > > - return ret;
> > > > ret = dm_i2c_read(dev, PCF2127_REG_CTRL1, buf,
> > > > sizeof(buf)); if (ret < 0)
> > > > return ret;
> > > > @@ -90,6 +84,13 @@ static int pcf2127_rtc_reset(struct udevice
> > > > *dev) return 0;
> > > > }
> > > >
> > > > +static int pcf2127_probe(struct udevice *dev) {
> > > > + i2c_set_chip_flags(dev, DM_I2C_CHIP_RD_NEED_STOP_BIT);
> > > > +
> > > > + return 0;
> > > > +}
> > > > +
> > > > static const struct rtc_ops pcf2127_rtc_ops = {
> > > > .get = pcf2127_rtc_get,
> > > > .set = pcf2127_rtc_set,
> > > > @@ -104,6 +105,7 @@ static const struct udevice_id
> > > > pcf2127_rtc_ids[] = { U_BOOT_DRIVER(rtc_pcf2127) = {
> > > > .name = "rtc-pcf2127",
> > > > .id = UCLASS_RTC,
> > > > + .probe = pcf2127_probe,
> > > > .of_match = pcf2127_rtc_ids,
> > > > .ops = &pcf2127_rtc_ops,
> > > > };
> > > > diff --git a/include/i2c.h b/include/i2c.h index
> > > > a5c760c711..beaa028349 100644
> > > > --- a/include/i2c.h
> > > > +++ b/include/i2c.h
> > > > @@ -28,6 +28,7 @@ enum dm_i2c_chip_flags {
> > > > DM_I2C_CHIP_10BIT = 1 << 0, /* Use 10-bit
> > > > addressing */ DM_I2C_CHIP_RD_ADDRESS = 1 << 1, /* Send
> > > > address for each read byte */ DM_I2C_CHIP_WR_ADDRESS = 1
> > > > << 2, /* Send address for each write byte */
> > > > + DM_I2C_CHIP_RD_NEED_STOP_BIT = 1 << 3, /* Need
> > > > generate stop bit */ };
> > > >
> > > > struct udevice;
> > > > @@ -87,6 +88,7 @@ enum dm_i2c_msg_flags {
> > > > I2C_M_IGNORE_NAK = 0x1000, /* continue after NAK
> > > > */ I2C_M_NO_RD_ACK = 0x0800, /* skip the Ack bit
> > > > on reads */ I2C_M_RECV_LEN = 0x0400, /* length is
> > > > first received byte */
> > > > + I2C_M_RD_NEED_STOP_BIT = 0x0002, /* need generate stop
> > > > bit */ };
> > > >
> > > > /**
> > >
> > >
> > >
> > >
> > > Best regards,
> > >
> > > Lukasz Majewski
> > >
> > > --
> > >
> > > DENX Software Engineering GmbH, Managing Director: Wolfgang
> > > Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell,
> > > Germany Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email:
> > > lukma at denx.de
>
>
>
>
> Best regards,
>
> Lukasz Majewski
>
> --
>
> DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email:
> lukma at denx.de