[linux-yocto] Regarding clarifications for adding support of I2C, SPI slave devices on x86 through ACPI

Wed Apr 16 03:31:04 PDT 2014

Thanks very much, Chia Ee and Boon leong. I will use this information.

Thanks,
B.Sathish Kumar

-----Original Message-----
From: Chew, Chiau Ee [mailto:chiau.ee.chew at intel.com] 
Sent: Wednesday, April 16, 2014 7:52 AM
To: Ong, Boon Leong; Sathish Kumar Balasubramaniam -ERS, HCL Tech
Cc: linux-yocto at yoctoproject.org; Darren Hart (dvhart at linux.intel.com); Chang, Rebecca Swee Fun
Subject: RE: [linux-yocto] Regarding clarifications for adding support of I2C, SPI slave devices on x86 through ACPI

> 1. Do we need any modification in the BIOS for adding support of I2C, 
> SPI slave devices to Linux using ACPI ?

  Yes, you need to add the slave device info like slave address, speed addressing mode, IRQ in the BIOS DSDT table.

> 2. Do we need to add the CONFIG_ACPI code (described in "I2C serial 
> bus support" section of acpi/enumeration.txt) to the 
> drivers/media/i2c/adv7180.c file ?

   Yes...the ACPI ID shall match with the one that you added into the BIOS DSDT table.

> 3. Where we need to add the device info like I2C bus number, I2C slave 
> address, IRQ ?

      In the BIOS DSDT table...using I2CSerialBus() resource descriptor to add the slave device info. You can refer to ACPI spec for the details of I2CSerialBus() resource descriptor.

> 4. Do we need to add any additional code in the chip driver     
> specifically for this ACPI support ?

Yes, refer to the "I2C serial bus support" section of acpi/enumeration.txt.

> 5. We have an Intel reference board. The source code provided by Intel 
> itself used certain board files to add support for SPI slave devices, 
> Clock setup, Init, etc. Why it has been done without using ACPI ? Is it due to any restriction ?

The board file is only needed if you are using PCI enumeration mode.

> -----Original Message-----
> From: Ong, Boon Leong
> Sent: Wednesday, April 16, 2014 7:32 AM
> To: Sathish Kumar Balasubramaniam -ERS, HCL Tech
> Cc: linux-yocto at yoctoproject.org; Darren Hart 
> (dvhart at linux.intel.com); Chang, Rebecca Swee Fun; Chew, Chiau Ee
> Subject: RE: [linux-yocto] Regarding clarifications for adding support 
> of I2C, SPI slave devices on x86 through ACPI
> 
> > -----Original Message-----
> > From: Sathish Kumar Balasubramaniam -ERS, HCL Tech [mailto:b- 
> > sathishkumar at hcl.com]
> > Sent: Wednesday, April 16, 2014 4:45 AM
> > To: Ong, Boon Leong
> > Cc: linux-yocto at yoctoproject.org; Darren Hart 
> > (dvhart at linux.intel.com); Chang, Rebecca Swee Fun; Chew, Chiau Ee
> > Subject: RE: [linux-yocto] Regarding clarifications for adding 
> > support of I2C, SPI slave devices on x86 through ACPI
> >
> > I could see addition of board files for baytrail in the git link you sent.
> >
> > By doubt is, why board files are still used in intel while the intel 
> > community itself does not recommend board files.
> >
> It is needed only in PCI enumeration. It is largely due to the clock 
> framework used by dma, spi & pwm which requires clock information to 
> be available/registered with the clock during PCI enumeration. This is 
> not needed for ACPI mode.
> 
> > I am referring
> > http://events.linuxfoundation.org/sites/events/files/slides/x86-
> > platform.pdf
> >
> > Correct me if i am wrong ?
> >
> Yes. The view/opinion of not having board file still stay.
> 
> > Regards,
> > B.Sathish Kumar
> > ________________________________________
> > From: Ong, Boon Leong [boon.leong.ong at intel.com]
> > Sent: 15 April 2014 20:28:14
> > To: Sathish Kumar Balasubramaniam -ERS, HCL Tech
> > Cc: linux-yocto at yoctoproject.org; Darren        Hart (dvhart at linux.intel.com);
> > Chang, Rebecca Swee Fun; Chew, Chiau Ee
> > Subject: RE: [linux-yocto] Regarding clarifications for adding 
> > support of I2C, SPI slave devices on x86 through ACPI
> >
> > CC'ed Rebecca & Chia Ee for their response/attention.
> >
> > Short answer, we have both ACPI and PCI enumeration support for 
> > those low power IO like I2C, SPI, HS-UART.
> > You can refer to
> > http://git.yoctoproject.org/cgit/cgit.cgi/linux-yocto-
> > 3.8/tree/meta/cfg/kernel-cache/features/valleyisland-io?h=meta for v3.8.
> >
> > For your knowledge, we are in the midst of making support for v3.10 
> > too and we prefer that your long term goal is to converge into Linux 
> > LTS/LTSI. But, it is fine to try out v3.8 and eventually move to v3.10.
> >
> >
> > From: linux-yocto-bounces at yoctoproject.org [mailto:linux-yocto- 
> > bounces at yoctoproject.org] On Behalf Of Sathish Kumar Balasubramaniam 
> > -ERS, HCL Tech
> > Sent: Tuesday, April 15, 2014 10:41 PM
> > To: linux-yocto at yoctoproject.org; Darren Hart 
> > (dvhart at linux.intel.com)
> > Subject: [linux-yocto] Regarding clarifications for adding support 
> > of I2C, SPI slave devices on x86 through ACPI
> > Importance: High
> >
> > Hi,
> >
> > For Intel, I can understand that the community is advising to 
> > implement the I2C, SPI slave devices info like base address, IRQs, 
> > etc through ACPI mechanism rather than using Board files and FDT
> >
> > I read the following
> > https://www.kernel.org/doc/Documentation/acpi/enumeration.txt
> > https://events.linuxfoundation.org/images/stories/slides/lfcs2013_wy
> > so
> > cki.pdf
> >
> > In Linux Kernel 3.8 we are trying to add support for (I2C, SPI) 
> > slave devices like video output decoder, video input decoder, etc 
> > which are behind the bus controllers
> >
> > For ex, for adding support of ADV7180 through I2C
> >
> > I have the following clarifications
> >
> > 1. Do we need any modification in the BIOS for adding support of 
> > I2C, SPI slave devices to Linux using ACPI ?
> > 2. Do we need to add the CONFIG_ACPI code (described in "I2C serial 
> > bus support" section of acpi/enumeration.txt) to the 
> > drivers/media/i2c/adv7180.c file ?
> > 3. Where we need to add the device info like I2C bus number, I2C 
> > slave address, IRQ ?
> > 4. Do we need to add any additional code in the chip driver 
> > specifically for this ACPI support ?
> > 5. We have an Intel reference board. The source code provided by 
> > Intel itself used certain board files to add support for SPI slave 
> > devices, Clock setup, Init, etc. Why it has been done without using 
> > ACPI ? Is it due to
> any restriction ?
> >
> >
> > Thanks,
> > B.Sathish Kumar
> >
> >
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