linux-kernel - Re: [RFC PATCH 5/5] fsi/scom: Major overhaul

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Date:   Sun, 17 Jun 2018 11:17:43 +1000
From:   Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:     Joel Stanley <joel@....id.au>
Cc:     OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Jeffery <andrew@...id.au>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [RFC PATCH 5/5] fsi/scom: Major overhaul

On Sat, 2018-06-16 at 14:34 +0930, Joel Stanley wrote:
> On 12 June 2018 at 14:49, Benjamin Herrenschmidt
> <benh@...nel.crashing.org> wrote:
> > This was too hard to split ... this adds a number of features
> > to the SCOM user interface:
> > 
> >  - Support for indirect SCOMs
> > 
> >  - read()/write() interface now handle errors and retries
> > 
> >  - New ioctl() "raw" interface for use by debuggers
> > 
> > Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> 
> Looks okay to me. I will put it in the openbmc tree with Eddie's ack
> for more testing.
> 
> I got a warning from the 0day infra, I made comments below.
> 
> We should get Alistair review the ioctl interface to ensure we have
> everything that pdbg might need.

We have everything that cronus needs and more than pdbg needs afaik :-)

That said, cronus does a bunch of other stupid things that I'm still
trying to figure out how to fix.

We might need to create a /dev/cfam rather than going through that
magic sysfs "raw" file, and I wouldn't mind using a single IDA so that
all the devices below a given FSI slace (cfam itself, sbefifo, occ,
...) have the same "number".

> 
> > +++ b/include/uapi/linux/fsi.h
> > @@ -0,0 +1,56 @@
> > +#ifndef _UAPI_LINUX_FSI_H
> > +#define _UAPI_LINUX_FSI_H
> > +
> > +#include <linux/ioctl.h>
> 
> This needs to include <linux/types.h> for the __u64 etc types.
> 
> We should also put a licence in the header. Probably:
> 
> /* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */

Yup.

Cheers,
Ben.

> 
> Cheers,
> 
> Joel
> 
> > +
> > +/*
> > + * /dev/scom "raw" ioctl interface
> > + *
> > + * The driver supports a high level "read/write" interface which
> > + * handles retries and converts the status to Linux error codes,
> > + * however low level tools an debugger need to access the "raw"
> > + * HW status information and interpret it themselves, so this
> > + * ioctl interface is also provided for their use case.
> > + */
> > +
> > +/* Structure for SCOM read/write */
> > +struct scom_access {
> > +       __u64   addr;           /* SCOM address, supports indirect */
> > +       __u64   data;           /* SCOM data (in for write, out for read) */
> > +       __u64   mask;           /* Data mask for writes */
> > +       __u32   intf_errors;    /* Interface error flags */
> > +#define SCOM_INTF_ERR_PARITY           0x00000001 /* Parity error */
> > +#define SCOM_INTF_ERR_PROTECTION       0x00000002 /* Blocked by secure boot */
> > +#define SCOM_INTF_ERR_ABORT            0x00000004 /* PIB reset during access */
> > +#define SCOM_INTF_ERR_UNKNOWN          0x80000000 /* Unknown error */
> > +       /*
> > +        * Note: Any other bit set in intf_errors need to be considered as an
> > +        * error. Future implementations may define new error conditions. The
> > +        * pib_status below is only valid if intf_errors is 0.
> > +        */
> > +       __u8    pib_status;     /* 3-bit PIB status */
> > +#define SCOM_PIB_SUCCESS       0       /* Access successful */
> > +#define SCOM_PIB_BLOCKED       1       /* PIB blocked, pls retry */
> > +#define SCOM_PIB_OFFLINE       2       /* Chiplet offline */
> > +#define SCOM_PIB_PARTIAL       3       /* Partial good */
> > +#define SCOM_PIB_BAD_ADDR      4       /* Invalid address */
> > +#define SCOM_PIB_CLK_ERR       5       /* Clock error */
> > +#define SCOM_PIB_PARITY_ERR    6       /* Parity error on the PIB bus */
> > +#define SCOM_PIB_TIMEOUT       7       /* Bus timeout */
> > +       __u8    pad;
> > +};
> > +
> > +/* Flags for SCOM check */
> > +#define SCOM_CHECK_SUPPORTED   0x00000001      /* Interface supported */
> > +#define SCOM_CHECK_PROTECTED   0x00000002      /* Interface blocked by secure boot */
> > +
> > +/* Flags for SCOM reset */
> > +#define SCOM_RESET_INTF                0x00000001      /* Reset interface */
> > +#define SCOM_RESET_PIB         0x00000002      /* Reset PIB */
> > +
> > +#define FSI_SCOM_CHECK _IOR('s', 0x00, __u32)
> > +#define FSI_SCOM_READ  _IOWR('s', 0x01, struct scom_access)
> > +#define FSI_SCOM_WRITE _IOWR('s', 0x02, struct scom_access)
> > +#define FSI_SCOM_RESET _IOW('s', 0x03, __u32)
> > +
> > +#endif /* _UAPI_LINUX_FSI_H */
> > --
> > 2.17.0
> >