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. > > >> > >>>> > >>>>>> 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. > > 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 -- 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: lu...@denx.de
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