Re: [PATCH v2 0/2] i2c:dw: Add APM X-Gene ACPI I2C device support

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Hi,

I'm not sure if this has been discussed earlier. But after looking at the the acpi_apd driver, all we need is just the platform-specific input clock frequency value used by the drivers/i2c/busses/i2c-designware-core.c: i2c_dw_init() to calculate the values to program into the DW_IC_SS_SCL_HCNT and DW_IC_SS_SCL_LCNT registers.

So, instead of hard-coding this value into the driver/acpi/acpi_apd.c (which really has nothing to do with the I2C driver), what if we introduce a new ACPI key-value pair in the ACPI DSDT such as:

    Device(I2C0)    // I2C controller
    {
      Name(_HID, "AMDI0510")
      Name(_UID, 0)
      Name(_CRS, ResourceTemplate() {
        Memory32Fixed (ReadWrite, 0xE1000000, 0x1000)
Interrupt (ResourceConsumer, Level, ActiveHigh, Exclusive,,,) { 389 } // GSIV
      })
      Name (_DSD, Package () {
        ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
        Package () {
          Package (2) {"clock-source-frequency", 100000000 }
        }
      }) // _DSD()
    }


Then, in the drivers/i2c/busses/i2c-designware-platdrv.c, we can add the code to parse this information. This way, the I2C driver can just retrieve this value from the ACPI table of each platform, which should make it easier to manage. Eventually, we can free I2C driver from the driver/acpi/acpi_apd.c, which is currently only used by AMD x86 platform.

Also, this approach would allow the I2C drivers in other OSes to use this same information in the ACPI table. If this approach is okay, I can provide a patch to implement this.

Thanks,
Suravee

On 12/10/2015 3:19 PM, Loc Ho wrote:
Add APM X-Gene ACPI I2C device support. These patches follow
the same implementation as AMD I2C driver - changes in ACPI APD
and Designware I2C drivers.

v2:
* Spilt the acpi_apd change with defines for AMD and X-Gene I2C's

Signed-off-by: Loc Ho <lho@xxxxxxx>
---
Loc Ho (2):
   acpi:apd: Add APM X-Gene ACPI I2C device support
   i2c:dw: Add APM X-Gene ACPI I2C device support

  drivers/acpi/acpi_apd.c                     |   16 +++++++++++++++-
  drivers/i2c/busses/i2c-designware-platdrv.c |    1 +
  2 files changed, 16 insertions(+), 1 deletions(-)

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