Hello Lukasz,
Am 23.05.2019 um 07:54 schrieb Lukasz Majewski:
Hi Heiko,
Hello Chuanhua Han,
Am 22.05.2019 um 14:45 schrieb Chuanhua Han:
-----Original Message-----
From: Lukasz Majewski <lu...@denx.de>
Sent: 2019年5月22日 19:32
To: Chuanhua Han <chuanhua....@nxp.com>
Cc: h...@denx.de; u-boot@lists.denx.de; Biwen Li <biwen...@nxp.com>;
s...@chromium.org; Stefano Babic <sba...@denx.de>
Subject: Re: [EXT] Re: [PATCH] i2c: pcf2127: fix bug that read
wrong time
On Wed, 22 May 2019 09:31:35 +0000
Chuanhua Han <chuanhua....@nxp.com> wrote:
-----Original Message-----
From: Lukasz Majewski <lu...@denx.de>
Sent: 2019年5月22日 16:41
To: Chuanhua Han <chuanhua....@nxp.com>
Cc: h...@denx.de; u-boot@lists.denx.de; Biwen Li
<biwen...@nxp.com>; s...@chromium.org; Stefano Babic
<sba...@denx.de> Subject: Re: [EXT] Re: [PATCH] i2c: pcf2127:
fix bug that read wrong time
Hi Chuanhua,
-----Original Message-----
From: Lukasz Majewski <lu...@denx.de>
Sent: 2019年5月22日 15:16
To: Chuanhua Han <chuanhua....@nxp.com>
Cc: h...@denx.de; u-boot@lists.denx.de; Biwen Li
<biwen...@nxp.com>; s...@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;
}
That was my point - the same shall be done in the pcf2127 driver.
This is a slow device, so we can afford for this.
There is no similar api in the uboot code to split the read data
into the address of the send register and receive the data. Uboot
encapsulates the transmit register address and the read data, so no
stop signal is generated.
If this API is missing, please introduce it. But not in one big patch
instead split it into:
- introduce I2C_M_RD_NEED_STOP_BIT
- support flag I2C_M_RD_NEED_STOP_BIT in driver drivers/i2c/mxc_i2c.c
or may we need a more common approach to this?
- pcf2127 driver changes
Also, as Lukasz mentioned, provide commit messages with more
information, what you do and why.
Verbose commit messages help with understanding the _real_ problem
being solved by the patch. Also are helpful in the future as a
documentation and reference.
Exactly.
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
Just one remark the mxc_i2c.c is IMX specific I2C code. Not the
generic one.
ok
Moreover, it looks like the same approach (first send, then read)
is performed in the pcf2127 driver at pcf2127_rtc_get() function.
I think that the driver shall be first thoroughly checked, then
fixes shall be added to it.
I have no such device, so hard to say ... and as Lukasz alread
mentioned the driver seems to make such an approach:
52 static int pcf2127_rtc_get(struct udevice *dev, struct rtc_time
*tm) 53 {
54 int ret = 0;
55 uchar buf[10] = { PCF2127_REG_CTRL1 };
56
57 ret = dm_i2c_write(dev, PCF2127_REG_CTRL1, buf, 1);
58 if (ret < 0)
59 return ret;
60 ret = dm_i2c_read(dev, PCF2127_REG_CTRL1, buf,
sizeof(buf)); 61 if (ret < 0)
62 return ret;
I would prefer to fix the issue in the driver itself. Only when it is
not possible we shall introduce extra flags and modify the common I2C
code.
If possible, yes! I wonder: if this driver is in mainline, it must
at least worked for Meng Yi (as driver author) ... unfortunately
the email address is not valid ... so removed him from cc list.
bye,
Heiko
It seems there are currently no real users of this driver:
pollux:u-boot hs [master] $ grep -lr RTC_PCF2127 .
./drivers/rtc/Kconfig
./drivers/rtc/Makefile
pollux:u-boot hs [master] $
I added Meng Yi to cc, as he is the author of this driver. May he
can say here more... at last I hope, the driver worked for him.
bye,
Heiko
Best regards,
Lukasz Majewski
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Phone: +49-8142-66989-52 Fax: +49-8142-66989-80 Email: h...@denx.de
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