Message-ID: <55916a03-2710-c8bc-0894-5a58daf6da68@huawei.com>
Date:   Tue, 31 Jan 2017 10:07:08 +0000
From:   John Garry <john.garry@...wei.com>
To:     Alexander Graf <agraf@...e.de>,
        "zhichang.yuan" <yuanzhichang@...ilicon.com>,
        <catalin.marinas@....com>, <will.deacon@....com>,
        <robh+dt@...nel.org>, <frowand.list@...il.com>,
        <bhelgaas@...gle.com>, <rafael@...nel.org>, <mark.rutland@....com>,
        <brian.starkey@....com>, <olof@...om.net>, <arnd@...db.de>,
        <linux-arm-kernel@...ts.infradead.org>
CC:     <lorenzo.pieralisi@....com>, <benh@...nel.crashing.org>,
        <linux-kernel@...r.kernel.org>, <linuxarm@...wei.com>,
        <devicetree@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        <linux-serial@...r.kernel.org>, <minyard@....org>,
        <liviu.dudau@....com>, <zourongrong@...il.com>,
        <gabriele.paoloni@...wei.com>, <zhichang.yuan02@...il.com>,
        <kantyzc@....com>, <xuwei5@...ilicon.com>
Subject: Re: [PATCH V6 4/5] LPC: Support the device-tree LPC host on
 Hip06/Hip07

On 30/01/2017 20:08, Alexander Graf wrote:
>

Alex,

Thanks for checking.

>
> On 24/01/2017 08:05, zhichang.yuan wrote:
>> The low-pin-count(LPC) interface of Hip06/Hip07 accesses the
>> peripherals in
>> I/O port addresses. This patch implements the LPC host controller
>> driver which
>> perform the I/O operations on the underlying hardware.
>> We don't want to touch those existing peripherals' driver, such as
>> ipmi-bt. So
>> this driver applies the indirect-IO introduced in the previous patch
>> after
>> registering an indirect-IO node to the indirect-IO devices list which
>> will be
>> searched in the I/O accessors.
>> As the I/O translations for LPC children depend on the host I/O
>> registration,
>> we should ensure the host I/O registration is finished before all the LPC
>> children scanning. That is why an arch_init() hook was added in this
>> patch.
>>
>> Signed-off-by: zhichang.yuan <yuanzhichang@...ilicon.com>
>> Signed-off-by: Gabriele Paoloni <gabriele.paoloni@...wei.com>
>> ---
>>  .../arm/hisilicon/hisilicon-low-pin-count.txt      |  33 ++
>>  MAINTAINERS                                        |   9 +
>>  arch/arm64/boot/dts/hisilicon/hip06-d03.dts        |   4 +
>>  arch/arm64/boot/dts/hisilicon/hip06.dtsi           |  14 +
>>  drivers/bus/Kconfig                                |   8 +
>>  drivers/bus/Makefile                               |   1 +
>>  drivers/bus/hisi_lpc.c                             | 599
>> +++++++++++++++++++++
>>  7 files changed, 668 insertions(+)
>>  create mode 100644
>> Documentation/devicetree/bindings/arm/hisilicon/hisilicon-low-pin-count.txt
>>
>>  create mode 100644 drivers/bus/hisi_lpc.c
>>
>> diff --git
>> a/Documentation/devicetree/bindings/arm/hisilicon/hisilicon-low-pin-count.txt
>> b/Documentation/devicetree/bindings/arm/hisilicon/hisilicon-low-pin-count.txt
>>
>> new file mode 100644
>> index 0000000..213181f
>> --- /dev/null
>> +++
>> b/Documentation/devicetree/bindings/arm/hisilicon/hisilicon-low-pin-count.txt
>>
>> @@ -0,0 +1,33 @@
>> +Hisilicon Hip06 low-pin-count device
>> +  Hisilicon Hip06 SoCs implement a Low Pin Count (LPC) controller, which
>> +  provides I/O access to some legacy ISA devices.
>> +  Hip06 is based on arm64 architecture where there is no I/O space.
>> So, the
>> +  I/O ports here are not cpu addresses, and there is no 'ranges'
>> property in
>> +  LPC device node.
>> +
>> +Required properties:
>> +- compatible:  value should be as follows:
>> +    (a) "hisilicon,hip06-lpc"
>> +    (b) "hisilicon,hip07-lpc"
>> +- #address-cells: must be 2 which stick to the ISA/EISA binding doc.
>> +- #size-cells: must be 1 which stick to the ISA/EISA binding doc.
>> +- reg: base memory range where the LPC register set is mapped.
>> +
>> +Note:
>> +  The node name before '@' must be "isa" to represent the binding
>> stick to the
>> +  ISA/EISA binding specification.
>> +
>> +Example:
>> +
>> +isa@...b0000 {
>> +    compatible = "hisilicon,hip06-lpc";
>> +    #address-cells = <2>;
>> +    #size-cells = <1>;
>> +    reg = <0x0 0xa01b0000 0x0 0x1000>;
>> +
>> +    ipmi0: bt@e4 {
>> +        compatible = "ipmi-bt";
>> +        device_type = "ipmi";
>> +        reg = <0x01 0xe4 0x04>;
>> +    };
>> +};
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index 26edd83..0153707 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -5855,6 +5855,15 @@ F:    include/uapi/linux/if_hippi.h
>>  F:    net/802/hippi.c
>>  F:    drivers/net/hippi/
>>
>> +HISILICON LPC BUS DRIVER
>> +M:    Zhichang Yuan <yuanzhichang@...ilicon.com>
>> +L:    linux-arm-kernel@...ts.infradead.org
>> +W:    http://www.hisilicon.com
>> +S:    Maintained
>> +F:    drivers/bus/hisi_lpc.c
>> +F:    lib/extio.c
>> +F:
>> Documentation/devicetree/bindings/arm/hisilicon/hisilicon-low-pin-count.txt
>>
>> +
>>  HISILICON NETWORK SUBSYSTEM DRIVER
>>  M:    Yisen Zhuang <yisen.zhuang@...wei.com>
>>  M:    Salil Mehta <salil.mehta@...wei.com>
>> diff --git a/arch/arm64/boot/dts/hisilicon/hip06-d03.dts
>> b/arch/arm64/boot/dts/hisilicon/hip06-d03.dts
>> index 7c4114a..75b2b5c 100644
>> --- a/arch/arm64/boot/dts/hisilicon/hip06-d03.dts
>> +++ b/arch/arm64/boot/dts/hisilicon/hip06-d03.dts
>> @@ -52,3 +52,7 @@
>>  &usb_ehci {
>>      status = "ok";
>>  };
>> +
>> +&ipmi0 {
>> +    status = "ok";
>> +};
>> diff --git a/arch/arm64/boot/dts/hisilicon/hip06.dtsi
>> b/arch/arm64/boot/dts/hisilicon/hip06.dtsi
>> index a049b64..c450f8d 100644
>> --- a/arch/arm64/boot/dts/hisilicon/hip06.dtsi
>> +++ b/arch/arm64/boot/dts/hisilicon/hip06.dtsi
>> @@ -318,6 +318,20 @@
>>          #size-cells = <2>;
>>          ranges;
>>
>> +        isa@...b0000 {
>> +            compatible = "hisilicon,hip06-lpc";
>> +            #size-cells = <1>;
>> +            #address-cells = <2>;
>> +            reg = <0x0 0xa01b0000 0x0 0x1000>;
>> +
>> +            ipmi0: bt@e4 {
>> +                compatible = "ipmi-bt";
>> +                device_type = "ipmi";
>> +                reg = <0x01 0xe4 0x04>;
>> +                status = "disabled";
>> +            };
>> +        };
>> +
>>          refclk: refclk {
>>              compatible = "fixed-clock";
>>              clock-frequency = <50000000>;
>> diff --git a/drivers/bus/Kconfig b/drivers/bus/Kconfig
>> index b9e8cfc..58cee84 100644
>> --- a/drivers/bus/Kconfig
>> +++ b/drivers/bus/Kconfig
>> @@ -64,6 +64,14 @@ config BRCMSTB_GISB_ARB
>>        arbiter. This driver provides timeout and target abort error
>> handling
>>        and internal bus master decoding.
>>
>> +config HISILICON_LPC
>> +    bool "Workaround for nonstandard ISA I/O space on Hisilicon Hip0X"
>
> It's not a workaround, it's support. Better word it like
>
>   "Support for ISA I/O space on Hisilicon HIP0X"
>

Agreed

>> +    depends on (ARM64 && ARCH_HISI && PCI) || COMPILE_TEST
>> +    select INDIRECT_PIO
>> +    help
>> +      Driver needed for some legacy ISA devices attached to
>> Low-Pin-Count
>> +      on Hisilicon Hip0X SoC.
>> +
>>  config IMX_WEIM
>>      bool "Freescale EIM DRIVER"
>>      depends on ARCH_MXC
>> diff --git a/drivers/bus/Makefile b/drivers/bus/Makefile
>> index cc6364b..28e3862 100644
>> --- a/drivers/bus/Makefile
>> +++ b/drivers/bus/Makefile
>> @@ -7,6 +7,7 @@ obj-$(CONFIG_ARM_CCI)        += arm-cci.o
>>  obj-$(CONFIG_ARM_CCN)        += arm-ccn.o
>>
>>  obj-$(CONFIG_BRCMSTB_GISB_ARB)    += brcmstb_gisb.o
>> +obj-$(CONFIG_HISILICON_LPC)    += hisi_lpc.o
>>  obj-$(CONFIG_IMX_WEIM)        += imx-weim.o
>>  obj-$(CONFIG_MIPS_CDMM)        += mips_cdmm.o
>>  obj-$(CONFIG_MVEBU_MBUS)     += mvebu-mbus.o
>> diff --git a/drivers/bus/hisi_lpc.c b/drivers/bus/hisi_lpc.c
>> new file mode 100644
>> index 0000000..a96e384
>> --- /dev/null
>> +++ b/drivers/bus/hisi_lpc.c
>> @@ -0,0 +1,599 @@
>> +/*
>> + * Copyright (C) 2016 Hisilicon Limited, All Rights Reserved.
>> + * Author: Zhichang Yuan <yuanzhichang@...ilicon.com>
>> + * Author: Zou Rongrong <zourongrong@...wei.com>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> + * GNU General Public License for more details.
>> + *
>> + * You should have received a copy of the GNU General Public License
>> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
>> + */
>> +
>> +#include <linux/acpi.h>
>> +#include <linux/console.h>
>> +#include <linux/delay.h>
>> +#include <linux/io.h>
>> +#include <linux/module.h>
>> +#include <linux/of.h>
>> +#include <linux/of_address.h>
>> +#include <linux/of_platform.h>
>> +#include <linux/pci.h>
>> +#include <linux/serial_8250.h>
>> +#include <linux/slab.h>
>> +
>> +/*
>> + * Setting this bit means each IO operation will target to a
>> + * different port address:
>> + * 0 means repeatedly IO operations will stick on the same port,
>> + * such as BT;
>> + */
>> +#define FG_INCRADDR_LPC        0x02
>> +
>> +struct lpc_cycle_para {
>> +    unsigned int opflags;
>> +    unsigned int csize; /* the data length of each operation */
>> +};
>> +
>> +struct hisilpc_dev {
>> +    spinlock_t cycle_lock;
>> +    void __iomem  *membase;
>> +    struct extio_node *extio;
>> +};
>> +
>> +/* bounds of the LPC bus address range */
>> +#define LPC_MIN_BUS_RANGE    0x0
>> +
>> +/*
>> + * The maximal IO size for each leagcy bus.
>
> legacy?
>
> I don't really understand why this bus is legacy though. It looks like a
> simple MMIO-to-LPC bridge to me.
>

I think that he means legacy ISA.

>> + * The port size of legacy I/O devices is normally less than 0x400.
>> + * Defining the I/O range size as 0x400 here should be sufficient for
>> + * all peripherals under one bus.
>> + */
>
> This comment doesn't make a lot of sense. What is the limit? Is there a
> hardware limit?
>
> We don't dynamically allocate devices on the lpc bus, so why imply a
> limit at all?
>

IIRC from previously asking Zhichang this before, this is the upper 
range we can address devices on the LPC bus. But the value was 0x1000 then.

>> +#define LPC_BUS_IO_SIZE        0x400
>> +
>> +/* The maximum continuous operations */
>> +#define LPC_MAX_OPCNT    16
>> +/* only support IO data unit length is four at maximum */
>> +#define LPC_MAX_DULEN    4
>> +#if LPC_MAX_DULEN > LPC_MAX_OPCNT
>> +#error "LPC.. MAX_DULEN must be not bigger than MAX_OPCNT!"
>> +#endif
>> +
>> +#define LPC_REG_START        0x00 /* start a new LPC cycle */
>> +#define LPC_REG_OP_STATUS    0x04 /* the current LPC status */
>> +#define LPC_REG_IRQ_ST        0x08 /* interrupt enable&status */
>> +#define LPC_REG_OP_LEN        0x10 /* how many LPC cycles each start */
>> +#define LPC_REG_CMD        0x14 /* command for the required LPC cycle */
>> +#define LPC_REG_ADDR        0x20 /* LPC target address */
>> +#define LPC_REG_WDATA        0x24 /* data to be written */
>> +#define LPC_REG_RDATA        0x28 /* data coming from peer */
>> +
>> +
>> +/* The command register fields */
>> +#define LPC_CMD_SAMEADDR    0x08
>> +#define LPC_CMD_TYPE_IO        0x00
>> +#define LPC_CMD_WRITE        0x01
>> +#define LPC_CMD_READ        0x00
>> +/* the bit attribute is W1C. 1 represents OK. */
>> +#define LPC_STAT_BYIRQ        0x02
>> +
>> +#define LPC_STATUS_IDLE        0x01
>> +#define LPC_OP_FINISHED        0x02
>> +
>> +#define START_WORK        0x01
>> +
>> +/*
>> + * The minimal waiting interval... Suggest it is not less than 10.
>> + * Bigger value probably will lower the performance.
>
> Are you sure you want this comment to be upstream? :)
>

We will remove or refine

>> + */
>> +#define LPC_NSEC_PERWAIT    100
>> +/*
>> + * The maximum waiting time is about 128us.
>> + * The fastest IO cycle time is about 390ns, but the worst case will
>> wait
>> + * for extra 256 lpc clocks, so (256 + 13) * 30ns = 8 us. The maximum
>> + * burst cycles is 16. So, the maximum waiting time is about 128us under
>> + * worst case.
>> + * choose 1300 as the maximum.
>> + */
>> +#define LPC_MAX_WAITCNT        1300
>> +/* About 10us. This is specific for single IO operation, such as inb. */
>> +#define LPC_PEROP_WAITCNT    100
>> +
>> +
>> +static inline int wait_lpc_idle(unsigned char *mbase,
>
> No need to specify inline.
>

Agreed

>> +                unsigned int waitcnt) {
>> +    u32 opstatus;
>> +
>> +    while (waitcnt--) {
>> +        ndelay(LPC_NSEC_PERWAIT);
>> +        opstatus = readl(mbase + LPC_REG_OP_STATUS);
>> +        if (opstatus & LPC_STATUS_IDLE)
>> +            return (opstatus & LPC_OP_FINISHED) ? 0 : (-EIO);
>
> It's a shame we have to busy loop, but I guess no calling code outside
> is prepared for rescheduling at this point.
>
>> +    }
>> +    return -ETIME;
>> +}
>> +
>> +/*
>> + * hisilpc_target_in - trigger a series of lpc cycles to read
>> required data
>> + *               from target peripheral.
>> + * @pdev: pointer to hisi lpc device
>> + * @para: some parameters used to control the lpc I/O operations
>> + * @ptaddr: the lpc I/O target port address
>> + * @buf: where the read back data is stored
>> + * @opcnt: how many I/O operations required in this calling
>> + *
>> + * Only one byte data is read each I/O operation.
>> + *
>> + * Returns 0 on success, non-zero on fail.
>> + *
>> + */
>> +static int
>> +hisilpc_target_in(struct hisilpc_dev *lpcdev, struct lpc_cycle_para
>> *para,
>> +          unsigned long ptaddr, unsigned char *buf,
>> +          unsigned long opcnt)
>> +{
>> +    unsigned long cnt_per_trans;
>> +    unsigned int cmd_word;
>> +    unsigned int waitcnt;
>> +    int ret;
>> +
>> +    if (!buf || !opcnt || !para || !para->csize || !lpcdev)
>> +        return -EINVAL;
>> +
>> +    if (opcnt  > LPC_MAX_OPCNT)
>> +        return -EINVAL;
>> +
>> +    cmd_word = LPC_CMD_TYPE_IO | LPC_CMD_READ;
>> +    waitcnt = LPC_PEROP_WAITCNT;
>> +    if (!(para->opflags & FG_INCRADDR_LPC)) {
>> +        cmd_word |= LPC_CMD_SAMEADDR;
>> +        waitcnt = LPC_MAX_WAITCNT;
>> +    }
>> +
>> +    ret = 0;
>> +    cnt_per_trans = (para->csize == 1) ? opcnt : para->csize;
>> +    for (; opcnt && !ret; cnt_per_trans = para->csize) {
>> +        unsigned long flags;
>> +
>> +        /* whole operation must be atomic */
>> +        spin_lock_irqsave(&lpcdev->cycle_lock, flags);
>
> Ouch. This is going to kill your RT jitter. Is there no better way?
>

Obviously the bus register driving is non-atomic, so we need some way to 
lock out.

I think that it is not so critical for low-speed/infrequent-access bus.

If we were going to use virtual UART in the BMC on the LPC bus then we 
could consider more.

>> +
>> +        writel(cnt_per_trans, lpcdev->membase + LPC_REG_OP_LEN);
>> +
>> +        writel(cmd_word, lpcdev->membase + LPC_REG_CMD);
>> +
>> +        writel(ptaddr, lpcdev->membase + LPC_REG_ADDR);
>> +
>> +        writel(START_WORK, lpcdev->membase + LPC_REG_START);
>> +
>> +        /* whether the operation is finished */
>> +        ret = wait_lpc_idle(lpcdev->membase, waitcnt);
>> +        if (!ret) {
>> +            opcnt -= cnt_per_trans;
>> +            for (; cnt_per_trans--; buf++)
>> +                *buf = readl(lpcdev->membase + LPC_REG_RDATA);
>> +        }
>> +
>> +        spin_unlock_irqrestore(&lpcdev->cycle_lock, flags);
>> +    }
>> +
>> +    return ret;
>> +}
>> +
>> +/**
>> + * hisilpc_target_out - trigger a series of lpc cycles to write required
>> + *            data to target peripheral.
>> + * @pdev: pointer to hisi lpc device
>> + * @para: some parameters used to control the lpc I/O operations
>> + * @ptaddr: the lpc I/O target port address
>> + * @buf: where the data to be written is stored
>> + * @opcnt: how many I/O operations required
>> + *
>> + * Only one byte data is read each I/O operation.
>> + *
>> + * Returns 0 on success, non-zero on fail.
>> + *
>> + */
>> +static int
>> +hisilpc_target_out(struct hisilpc_dev *lpcdev, struct lpc_cycle_para
>> *para,
>> +           unsigned long ptaddr, const unsigned char *buf,
>> +           unsigned long opcnt)
>> +{
>> +    unsigned long cnt_per_trans;
>> +    unsigned int cmd_word;
>> +    unsigned int waitcnt;
>> +    int ret;
>> +
>> +    if (!buf || !opcnt || !para || !lpcdev)
>> +        return -EINVAL;
>> +
>> +    if (opcnt > LPC_MAX_OPCNT)
>> +        return -EINVAL;
>> +    /* default is increasing address */
>> +    cmd_word = LPC_CMD_TYPE_IO | LPC_CMD_WRITE;
>> +    waitcnt = LPC_PEROP_WAITCNT;
>> +    if (!(para->opflags & FG_INCRADDR_LPC)) {
>> +        cmd_word |= LPC_CMD_SAMEADDR;
>> +        waitcnt = LPC_MAX_WAITCNT;
>> +    }
>> +
>> +    ret = 0;
>> +    cnt_per_trans = (para->csize == 1) ? opcnt : para->csize;
>> +    for (; opcnt && !ret; cnt_per_trans = para->csize) {
>> +        unsigned long flags;
>> +
>> +        spin_lock_irqsave(&lpcdev->cycle_lock, flags);
>
> Same thing here
>

As above

>> +
>> +        writel(cnt_per_trans, lpcdev->membase + LPC_REG_OP_LEN);
>> +        opcnt -= cnt_per_trans;
>> +        for (; cnt_per_trans--; buf++)
>> +            writel(*buf, lpcdev->membase + LPC_REG_WDATA);
>> +
>> +        writel(cmd_word, lpcdev->membase + LPC_REG_CMD);
>> +
>> +        writel(ptaddr, lpcdev->membase + LPC_REG_ADDR);
>> +
>> +        writel(START_WORK, lpcdev->membase + LPC_REG_START);
>> +
>> +        /* whether the operation is finished */
>> +        ret = wait_lpc_idle(lpcdev->membase, waitcnt);
>> +
>> +        spin_unlock_irqrestore(&lpcdev->cycle_lock, flags);
>> +    }
>> +
>> +    return ret;
>> +}
>> +
>> +static inline unsigned long
>
> Don't explicitly mention inline, the compiler will figure that out for you.
>

Sure

>> +hisi_lpc_pio_to_addr(struct hisilpc_dev *lpcdev, unsigned long pio)
>> +{
>> +    return pio - lpcdev->extio->io_start + lpcdev->extio->bus_start;
>> +}
>> +
>> +
>> +/**
>> + * hisilpc_comm_in - read/input the data from the I/O peripheral
>> + *             through LPC.
>> + * @devobj: pointer to the device information relevant to LPC
>> controller.
>> + * @pio: the target I/O port address.
>> + * @dlen: the data length required to read from the target I/O port.
>> + *
>> + * when succeed, the data read back is stored in buffer pointed by
>> inbuf.
>> + * For inb, return the data read from I/O or -1 when error occur.
>> + */
>> +static u64 hisilpc_comm_in(void *devobj, unsigned long pio, size_t dlen)
>> +{
>> +    struct hisilpc_dev *lpcdev = devobj;
>> +    struct lpc_cycle_para iopara;
>> +    u32 rd_data;
>
> rd_data needs to be initialized to 0. Otherwise it may contain stale
> stack contents and corrupt non-32bit dlen returns.
>

I think so, since we read into this value byte-by-byte. We also seem to 
return a 32b value but should return 64b value according to the prototype.

>> +    unsigned char *newbuf;
>> +    int ret = 0;
>> +    unsigned long ptaddr;
>> +
>> +    if (!lpcdev || !dlen || dlen > LPC_MAX_DULEN ||    (dlen & (dlen
>> - 1)))
>> +        return -1;
>
> Isn't this -EINVAL?

Not sure. This value is returned directly to the inb/outb caller, which 
would not check this value for error.

It could be argued that the checking is paranoia. If not, we should 
treat the failure as a more severe event.

>
>> +
>> +    /* the local buffer must be enough for one data unit */
>> +    if (sizeof(rd_data) < dlen)
>> +        return -1;
>
> Same here.
>
> Also, the above seems a very convoluted way of saying
>
>   switch (dlen) {
>   case 1:
>   case 2:
>   case 4:

It's better

>     break;
>   default:
>     return -EINVAL;
>   }
>
> But I guess the way you write it doesn't hurt ;)
>
>
> Alex
>
> .
>

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