Re: [PATCH v3 1/3] xen/arm: Add imx8q{m,x} platform glue

[Michal Orzel <michal.orzel@xxxxxxx>]

Hi John,

On 28/03/2024 17:34, John Ernberg wrote:
> 
> 
> When using Linux for dom0 there are a bunch of drivers that need to do SMC
> SIP calls into the firmware to enable certain hardware bits like the
> watchdog.
> 
> Provide a basic platform glue that implements the needed SMC forwarding.
> 
> The format of these calls are as follows:
>  - reg 0: function ID
>  - reg 1: subfunction ID (when there's a subfunction)
>  remaining regs: args
> 
> For now we only allow Dom0 to make these calls as they are all managing
> hardware. There is no specification for these SIP calls, the IDs and names
> have been extracted from the upstream linux kernel and the vendor kernel.
> 
> Most of the SIP calls are only available for the iMX8M series of SoCs, so
> they are easy to reject and they need to be revisited when iMX8M series
> support is added.
I just realized that you pinged me in v2 for clarification, sorry I missed that.
I still believe we shouldn't list FIDs that are meant for IMX8M, given that
the driver is written for IMX8QM/QXP.

> 
> From the other calls we can reject CPUFREQ because Dom0 cannot make an
> informed decision regarding CPU frequency scaling, WAKEUP_SRC is to wake
> up from suspend, which Xen doesn't support at this time.
> 
> This leaves the TIME SIP, OTP SIPs, BUILDINFO SIP and TEMP ALARM SIP, which
> for now are allowed to Dom0.
> 
> NOTE: This code is based on code found in NXP Xen tree located here:
> https://github.com/nxp-imx/imx-xen/blob/lf-5.10.y_4.13/xen/arch/arm/platforms/imx8qm.c
> 
> Signed-off-by: Peng Fan <peng.fan@xxxxxxx>
> [jernberg: Add SIP call filtering]
> Signed-off-by: John Ernberg <john.ernberg@xxxxxxxx>
> 
> ---
> 
> v3:
>  - Adhere to style guidelines for line length and label indentation (Michal 
> Orzel)
>  - Use smccc macros to build the SIP function identifier (Michal Orzel)
>  - Adjust platform name to be specific to QM and QXP variants (Michal Orzel)
>  - Pick up additional SIPs which may be used by other Linux versions - for 
> review purposes
>  - Changes to the commit message due to above
> 
> v2:
>  - Reword the commit message to be a bit clearer
>  - Include the link previously added as a context note to the commit message 
> (Julien Grall)
>  - Add Pengs signed off (Julien Grall, Peng Fan)
>  - Add basic SIP call filter (Julien Grall)
>  - Expand the commit message a whole bunch because of the changes to the code
> ---
>  xen/arch/arm/platforms/Makefile |   1 +
>  xen/arch/arm/platforms/imx8qm.c | 168 ++++++++++++++++++++++++++++++++
>  2 files changed, 169 insertions(+)
>  create mode 100644 xen/arch/arm/platforms/imx8qm.c
> 
> diff --git a/xen/arch/arm/platforms/Makefile b/xen/arch/arm/platforms/Makefile
> index 8632f4115f..bec6e55d1f 100644
> --- a/xen/arch/arm/platforms/Makefile
> +++ b/xen/arch/arm/platforms/Makefile
> @@ -9,5 +9,6 @@ obj-$(CONFIG_ALL_PLAT)   += sunxi.o
>  obj-$(CONFIG_ALL64_PLAT) += thunderx.o
>  obj-$(CONFIG_ALL64_PLAT) += xgene-storm.o
>  obj-$(CONFIG_ALL64_PLAT) += brcm-raspberry-pi.o
> +obj-$(CONFIG_ALL64_PLAT) += imx8qm.o
>  obj-$(CONFIG_MPSOC_PLATFORM)  += xilinx-zynqmp.o
>  obj-$(CONFIG_MPSOC_PLATFORM)  += xilinx-zynqmp-eemi.o
> diff --git a/xen/arch/arm/platforms/imx8qm.c b/xen/arch/arm/platforms/imx8qm.c
> new file mode 100644
> index 0000000000..0992475474
> --- /dev/null
> +++ b/xen/arch/arm/platforms/imx8qm.c
> @@ -0,0 +1,168 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * xen/arch/arm/platforms/imx8qm.c
> + *
> + * i.MX 8QM setup
> + *
> + * Copyright (c) 2016 Freescale Inc.
> + * Copyright 2018-2019 NXP
> + *
> + *
> + * Peng Fan <peng.fan@xxxxxxx>
> + */
> +
> +#include <xen/sched.h>
> +#include <asm/platform.h>
> +#include <asm/smccc.h>
> +
> +static const char * const imx8qm_dt_compat[] __initconst =
> +{
> +    "fsl,imx8qm",
> +    "fsl,imx8qxp",
> +    NULL
> +};
> +
> +#define IMX_SIP_FID(fid) \
> +    ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
> +                       ARM_SMCCC_CONV_64, \
> +                       ARM_SMCCC_OWNER_SIP, \
> +                       fid)
macro parameter should be enclosed within parenthesis

> +
> +#define IMX_SIP_F_GPC            0x0000
> +#define IMX_SIP_F_CPUFREQ        0x0001
> +#define IMX_SIP_F_TIME           0x0002
> +#define IMX_SIP_F_BUILDINFO      0x0003
> +#define IMX_SIP_F_DDR_DVFS       0x0004
> +#define IMX_SIP_F_SRC            0x0005
> +#define IMX_SIP_F_GET_SOC_INFO   0x0006
> +#define IMX_SIP_F_NOC            0x0008
> +#define IMX_SIP_F_WAKEUP_SRC     0x0009
> +#define IMX_SIP_F_OTP_READ       0x000A
> +#define IMX_SIP_F_OTP_WRITE      0x000B
> +#define IMX_SIP_F_SET_TEMP_ALARM 0x000C
Is there specific reason for leading zeros?

> +
> +#define IMX_SIP_TIME_SF_RTC_SET_TIME     0x00
> +#define IMX_SIP_TIME_SF_WDOG_START       0x01
> +#define IMX_SIP_TIME_SF_WDOG_STOP        0x02
> +#define IMX_SIP_TIME_SF_WDOG_SET_ACT     0x03
> +#define IMX_SIP_TIME_SF_WDOG_PING        0x04
> +#define IMX_SIP_TIME_SF_WDOG_SET_TIMEOUT 0x05
> +#define IMX_SIP_TIME_SF_WDOG_GET_STAT    0x06
> +#define IMX_SIP_TIME_SF_WDOG_SET_PRETIME 0x07
> +
> +static bool imx8qm_is_sip_time_call_ok(uint32_t subfunction_id)
> +{
> +    switch ( subfunction_id )
> +    {
> +    case IMX_SIP_TIME_SF_RTC_SET_TIME:
> +        return true;
> +    case IMX_SIP_TIME_SF_WDOG_START:
> +    case IMX_SIP_TIME_SF_WDOG_STOP:
> +    case IMX_SIP_TIME_SF_WDOG_SET_ACT:
> +    case IMX_SIP_TIME_SF_WDOG_PING:
> +    case IMX_SIP_TIME_SF_WDOG_SET_TIMEOUT:
> +    case IMX_SIP_TIME_SF_WDOG_GET_STAT:
> +    case IMX_SIP_TIME_SF_WDOG_SET_PRETIME:
> +        return true;
> +    default:
> +        printk(XENLOG_WARNING "imx8qm: smc: time: Unknown subfunction id 
> %x\n",
gprintk

> +               subfunction_id);
> +        return false;
> +    }
> +}
> +
> +static bool imx8qm_smc(struct cpu_user_regs *regs)
> +{
> +    uint32_t function_id = get_user_reg(regs, 0);
> +    uint32_t subfunction_id = get_user_reg(regs, 1);
> +    struct arm_smccc_res res;
> +
> +    if ( !cpus_have_const_cap(ARM_SMCCC_1_1) )
> +    {
> +        printk_once(XENLOG_WARNING "no SMCCC 1.1 support. Disabling firmware 
> calls\n");
NIT: you can move string within quotes to the next line to avoid exceeding 80 
chars.
Also, all the other messages are prepended with "imx8qm: smc:" so better be 
consistent.

> +
> +        return false;
> +    }
> +
> +    /* Only hardware domain may use the SIP calls */
> +    if ( !is_hardware_domain(current->domain) )
> +    {
> +        gprintk(XENLOG_WARNING, "imx8qm: smc: No access\n");
Here you use gprintk, but ...

> +        return false;
> +    }
> +
> +    switch ( function_id )
> +    {
> +    /* Only available on imx8m series */
> +    case IMX_SIP_FID(IMX_SIP_F_GPC):
> +        return false;
> +    case IMX_SIP_FID(IMX_SIP_F_CPUFREQ):
> +        /* Hardware domain can't take any informed decision here */
> +        return false;
> +    case IMX_SIP_FID(IMX_SIP_F_BUILDINFO):
> +        goto allow_call;
> +    case IMX_SIP_FID(IMX_SIP_F_TIME):
> +        if ( imx8qm_is_sip_time_call_ok(subfunction_id) )
> +            goto allow_call;
> +        return false;
> +    /* Only available on imx8m series */
> +    case IMX_SIP_FID(IMX_SIP_F_DDR_DVFS):
> +        return false;
> +    /* Only available on imx8m series */
> +    case IMX_SIP_FID(IMX_SIP_F_SRC):
> +        return false;
> +    /* Only available on imx8m series */
> +    case IMX_SIP_FID(IMX_SIP_F_GET_SOC_INFO):
> +        return false;
> +    /* Only available on imx8m series */
> +    case IMX_SIP_FID(IMX_SIP_F_NOC):
> +        return false;
> +    /* Xen doesn't have suspend support */
> +    case IMX_SIP_FID(IMX_SIP_F_WAKEUP_SRC):
> +        return false;
> +    case IMX_SIP_FID(IMX_SIP_F_OTP_READ):
> +        /* subfunction_id is the fuse number, no sensible check possible */
> +        goto allow_call;
> +    case IMX_SIP_FID(IMX_SIP_F_OTP_WRITE):
> +        /* subfunction_id is the fuse number, no sensible check possible */
> +        goto allow_call;
> +    case IMX_SIP_FID(IMX_SIP_F_SET_TEMP_ALARM):
> +        goto allow_call;
> +    default:
> +        printk(XENLOG_WARNING "imx8qm: smc: Unknown function id %x\n",
... here you don't.

> +               function_id);
> +        return false;
> +    }
> +
> + allow_call:
> +    arm_smccc_1_1_smc(function_id,
> +                      subfunction_id,
> +                      get_user_reg(regs, 2),
> +                      get_user_reg(regs, 3),
> +                      get_user_reg(regs, 4),
> +                      get_user_reg(regs, 5),
> +                      get_user_reg(regs, 6),
> +                      get_user_reg(regs, 7),
> +                      &res);
> +
> +    set_user_reg(regs, 0, res.a0);
> +    set_user_reg(regs, 1, res.a1);
> +    set_user_reg(regs, 2, res.a2);
> +    set_user_reg(regs, 3, res.a3);
> +
> +    return true;
> +}
> +
> +PLATFORM_START(imx8qm, "i.MX 8Q{M,XP}")
> +    .compatible = imx8qm_dt_compat,
> +    .smc = imx8qm_smc,
> +PLATFORM_END
> +
> +/*
> + * Local variables:
> + * mode: C
> + * c-file-style: "BSD"
> + * c-basic-offset: 4
> + * indent-tabs-mode: nil
> + * End:
> + */
> --
> 2.44.0


~Michal