Re: [PATCH v6 3/7] mfd: Add support for the Lantiq PEF2256 framer

21 Apr 2023


      Hi Lee, Krzysztof,
On Thu, 20 Apr 2023 14:47:03 +0100
Lee Jones lee@kernel.org wrote:
...
On Thu, 20 Apr 2023, Herve Codina wrote:
...
On Thu, 20 Apr 2023 13:39:46 +0100
Lee Jones lee@kernel.org wrote:
...
On Mon, 17 Apr 2023, Herve Codina wrote:
...
The Lantiq PEF2256 is a framer and line interface component designed to
fulfill all required interfacing between an analog E1/T1/J1 line and the
digital PCM system highway/H.100 bus.
Signed-off-by: Herve Codina herve.codina@bootlin.com
drivers/mfd/Kconfig         |  16 +
 drivers/mfd/Makefile        |   1 +
 drivers/mfd/pef2256-regs.h  | 250 ++++++++++
 drivers/mfd/pef2256.c       | 950 ++++++++++++++++++++++++++++++++++++
95% of this driver needs to be moved somewhere else.
What is a Framer?  Perhaps sound/ is a good candidate?
The pef2256 framer is a device that transfers data to/from a TDM (time-slots
data) from/to quite old telecommunication lines (E1 in my case).
Several subsystem can set/get data to/from the TDM. Each device using their
own time-slots set.
On my use-case, I have some audio consumer and a not yet upstreamed HDLC
consumer. Both of them uses the framer to know the E1 link state.
The framer needs to be initialized 'globally' and not by a specific consumer
as several consumers can use the framer.
I can't think of a good place for this.
If all else fails, it's drivers/misc
...
...
...
include/linux/mfd/pef2256.h |  52 ++
 5 files changed, 1269 insertions(+)
 create mode 100644 drivers/mfd/pef2256-regs.h
 create mode 100644 drivers/mfd/pef2256.c
 create mode 100644 include/linux/mfd/pef2256.h
[...]
...
+static int pef2256_add_audio_devices(struct pef2256 *pef2256)
+{

const char *compatible = "lantiq,pef2256-codec";
struct mfd_cell *audio_devs;
struct device_node *np;
unsigned int count = 0;
unsigned int i;
int ret;

for_each_available_child_of_node(pef2256->dev->of_node, np) {
if (of_device_is_compatible(np, compatible))


	count++;


}

Converting Device Tree nodes into MFD cells to register with the
Platform Device API is not a reasonable use-case of MFD.
Have the CODEC driver match on "lantiq,pef2256-codec" and let it
instantiate itself.
As the framer is going to used by several subsystem, I cannot instantiate
it in the specific ASoC subsystem.
...
Your first version using of_platform_populate() was closer to the mark.
The issue was that I need MFD cells for the pinctrl part.
Why can't it be represented in DT?
The pinctrl part has no specific compatible string.
Not sure that a compatible string for pinctrl can be accepted
as there is only one pinctrl subnode and no specific reg for this
subnode.
The DT looks like this:
    framer@2000000 {
      compatible = "lantiq,pef2256";
      reg = <0x2000000 0x100>;
      ...
      pinctrl {
        pef2256_rpa_sypr: rpa-pins {
          pins = "RPA";
          function = "SYPR";
        };
      };
pef2256_codec0: codec-0 {
        compatible = "lantiq,pef2256-codec";
        #sound-dai-cells = <0>;
        sound-name-prefix = "PEF2256_0";
      };
    };
Krzysztof, is it acceptable to have a compatible string in the pinctrl node ?
In this case, it will looks like this:
    framer@2000000 {
      compatible = "lantiq,pef2256";
      reg = <0x2000000 0x100>;
      ...
      pinctrl {
        compatible = "lantiq,pef2256-pinctrl";
        pef2256_rpa_sypr: rpa-pins {
          pins = "RPA";
          function = "SYPR";
        };
      };
pef2256_codec0: codec-0 {
        compatible = "lantiq,pef2256-codec";
        #sound-dai-cells = <0>;
        sound-name-prefix = "PEF2256_0";
      };
    };
Best regards,
Hervé