From: "Wang, Haiyue" <haiyue.wang@linux.intel.com>
Subject: Re: [PATCH arm/aspeed/ast2500 v1] ipmi: add an Aspeed KCS IPMI BMC
 driver
To: minyard@acm.org, joel@jms.id.au, openbmc@lists.ozlabs.org,
        openipmi-developer@lists.sourceforge.net,
        linux-kernel@vger.kernel.org
Cc: andriy.shevchenko@intel.com
References: <1516103023-19244-1-git-send-email-haiyue.wang@linux.intel.com>
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Message-ID: <e462c75e-8d93-cddf-06f9-f40643e5b703@linux.intel.com>
Date: Wed, 17 Jan 2018 22:31:08 +0800
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On 2018-01-17 06:12, Corey Minyard wrote:
> On 01/16/2018 02:59 PM, Corey Minyard wrote:
>> On 01/16/2018 05:43 AM, Haiyue Wang wrote:
>>> The KCS (Keyboard Controller Style) interface is used to perform 
>>> in-band
>>> IPMI communication between a server host and its BMC (BaseBoard 
>>> Management
>>> Controllers).
>>>
>>> This driver exposes the KCS interface on ASpeed SOCs (AST2400 and 
>>> AST2500)
>>> as a character device. Such SOCs are commonly used as BMCs and this 
>>> driver
>>> implements the BMC side of the KCS interface.
>>
>> I thought we were going to unify the BMC ioctl interface?  My 
>> preference would be to
>> create a file named include/uapi/linux/ipmi-bmc.h and add the following:
>>
>> #define __IPMI_BMC_IOCTL_MAGIC    0xb1
>> #define IPMI_BMC_IOCTL_SMS_SET_ATN _IO(__IPMI_BMC_IOCTL_MAGIC, 0x00)
>>
>> to make it the same as BT.  Then in bt-bmc.h, set 
>> BT_BMC_IOCTL_SMS_ATN to
>> IPMI_BMC_IOCTL_SMS_SET_ATN.  Then add the KCS ioctls in ipmi-bmc.h and
>> use that.  That way we stay backward compatible but we are unified.
>>
>> Since more KCS interfaces may come around, can you make the name more
>> specific?  (I made this same error on bt-bmc,c, it should probably be 
>> renamed.)
>>
How about these IOCTL definitions ? Is it more specific ?

#define IPMI_BMC_IOCTL_SET_SMS_ATN    _IO(__IPMI_BMC_IOCTL_MAGIC, 0x00)
#define IPMI_BMC_IOCTL_CLEAR_SMS_ATN  _IO(__IPMI_BMC_IOCTL_MAGIC, 0x01)
#define IPMI_BMC_IOCTL_FORCE_ABORT    _IO(__IPMI_BMC_IOCTL_MAGIC, 0x02)

>> More comments inline, as I'll go ahead and review this.
>>
>>> Signed-off-by: Haiyue Wang <haiyue.wang@linux.intel.com>
>>> ---
>>>   .../devicetree/bindings/ipmi/aspeed-kcs-bmc.txt    |  26 +
>>>   drivers/char/ipmi/Kconfig                          |   9 +
>>>   drivers/char/ipmi/Makefile                         |   1 +
>>>   drivers/char/ipmi/kcs-bmc.c                        | 744 
>>> +++++++++++++++++++++
>>>   include/uapi/linux/kcs-bmc.h                       |  14 +
>>>   5 files changed, 794 insertions(+)
>>>   create mode 100644 
>>> Documentation/devicetree/bindings/ipmi/aspeed-kcs-bmc.txt
>>>   create mode 100644 drivers/char/ipmi/kcs-bmc.c
>>>   create mode 100644 include/uapi/linux/kcs-bmc.h
>>>
>>> diff --git 
>>> a/Documentation/devicetree/bindings/ipmi/aspeed-kcs-bmc.txt 
>>> b/Documentation/devicetree/bindings/ipmi/aspeed-kcs-bmc.txt
>>> new file mode 100644
>>> index 0000000..dd0c73d
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/ipmi/aspeed-kcs-bmc.txt
>>> @@ -0,0 +1,26 @@
>>> +* Aspeed KCS (Keyboard Controller Style) IPMI interface
>>> +
>>> +The Aspeed SOCs (AST2400 and AST2500) are commonly used as BMCs
>>> +(BaseBoard Management Controllers) and the KCS interface can be
>>> +used to perform in-band IPMI communication with their host.
>>> +
>>> +Required properties:
>>> +- compatible : should be one of
>>> +    "aspeed,ast2400-kcs-bmc"
>>> +    "aspeed,ast2500-kcs-bmc"
>>> +- interrupts : interrupt generated by the controller
>>> +- kcs_chan : The LPC channel number in the controller
>>> +- kcs_addr : The host CPU IO map address
>>> +
>>> +
>>> +Example:
>>> +
>>> +    kcs3: kcs3@0 {
>>> +        compatible = "aspeed,ast2500-kcs-bmc";
>>> +        reg = <0x0 0x80>;
>>> +        interrupts = <8>;
>>> +        kcs_chan = <3>;
>>> +        kcs_addr = <0xCA2>;
>>> +        status = "okay";
>>> +    };
>>> +
>>> diff --git a/drivers/char/ipmi/Kconfig b/drivers/char/ipmi/Kconfig
>>> index 3544abc..36132f8 100644
>>> --- a/drivers/char/ipmi/Kconfig
>>> +++ b/drivers/char/ipmi/Kconfig
>>> @@ -104,3 +104,12 @@ config ASPEED_BT_IPMI_BMC
>>>         Provides a driver for the BT (Block Transfer) IPMI interface
>>>         found on Aspeed SOCs (AST2400 and AST2500). The driver
>>>         implements the BMC side of the BT interface.
>>> +
>>> +config ASPEED_KCS_IPMI_BMC
>>> +    depends on ARCH_ASPEED || COMPILE_TEST
>>> +    select REGMAP_MMIO
>>> +    tristate "KCS IPMI bmc driver"
>>> +    help
>>> +      Provides a driver for the KCS (Keyboard Controller Style) IPMI
>>> +      interface found on Aspeed SOCs (AST2400 and AST2500). The driver
>>> +      implements the BMC side of the KCS interface.
>>> \ No newline at end of file
>>> diff --git a/drivers/char/ipmi/Makefile b/drivers/char/ipmi/Makefile
>>> index 33b899f..f217bae 100644
>>> --- a/drivers/char/ipmi/Makefile
>>> +++ b/drivers/char/ipmi/Makefile
>>> @@ -22,3 +22,4 @@ obj-$(CONFIG_IPMI_POWERNV) += ipmi_powernv.o
>>>   obj-$(CONFIG_IPMI_WATCHDOG) += ipmi_watchdog.o
>>>   obj-$(CONFIG_IPMI_POWEROFF) += ipmi_poweroff.o
>>>   obj-$(CONFIG_ASPEED_BT_IPMI_BMC) += bt-bmc.o
>>> +obj-$(CONFIG_ASPEED_KCS_IPMI_BMC) += kcs-bmc.o
>>> \ No newline at end of file
>>> diff --git a/drivers/char/ipmi/kcs-bmc.c b/drivers/char/ipmi/kcs-bmc.c
>>> new file mode 100644
>>> index 0000000..d6eab0b
>>> --- /dev/null
>>> +++ b/drivers/char/ipmi/kcs-bmc.c
>>> @@ -0,0 +1,744 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +// Copyright (c) 2015-2018, Intel Corporation.
>>> +
>>> +#include <linux/atomic.h>
>>> +#include <linux/errno.h>
>>> +#include <linux/interrupt.h>
>>> +#include <linux/io.h>
>>> +#include <linux/kcs-bmc.h>
>>> +#include <linux/mfd/syscon.h>
>>> +#include <linux/miscdevice.h>
>>> +#include <linux/module.h>
>>> +#include <linux/of.h>
>>> +#include <linux/platform_device.h>
>>> +#include <linux/poll.h>
>>> +#include <linux/regmap.h>
>>> +#include <linux/sched.h>
>>> +#include <linux/slab.h>
>>> +#include <linux/timer.h>
>>> +
>>> +#define KCS_MSG_BUFSIZ      1024
>>> +#define KCS_CHANNEL_MAX     4
>>> +
>>> +/*
>>> + * This is a BMC device used to communicate to the host
>>> + */
>>> +#define DEVICE_NAME     "ipmi-kcs-host"
>>> +
>>> +
>>> +/* Different Phases of the KCS Module */
>>> +#define KCS_PHASE_IDLE          0x00
>>> +#define KCS_PHASE_WRITE         0x01
>>> +#define KCS_PHASE_WRITE_END     0x02
>>> +#define KCS_PHASE_READ          0x03
>>> +#define KCS_PHASE_ABORT         0x04
>>> +#define KCS_PHASE_ERROR         0x05
>>
>> It would be nicer to make the above an enum.
>>
Done!
>>> +
>>> +/* Abort Phase */
>>> +#define ABORT_PHASE_ERROR1      0x01
>>> +#define ABORT_PHASE_ERROR2      0x02
>>
>> Can the above just be folded into two separate phases in kcs_phase?
>> That would be a little cleaner.
>>
Done, the code is truly cleaner, thanks! ;-)
>>
>>> +
>>> +/* KCS Command Control codes. */
>>> +#define KCS_GET_STATUS          0x60
>>> +#define KCS_ABORT               0x60
>>> +#define KCS_WRITE_START         0x61
>>> +#define KCS_WRITE_END           0x62
>>> +#define KCS_READ_BYTE           0x68
>>> +
>>> +/* Status bits.:
>>> + * - IDLE_STATE.  Interface is idle. System software should not be 
>>> expecting
>>> + *                nor sending any data.
>>> + * - READ_STATE.  BMC is transferring a packet to system software. 
>>> System
>>> + *                software should be in the "Read Message" state.
>>> + * - WRITE_STATE. BMC is receiving a packet from system software. 
>>> System
>>> + *                software should be writing a command to the BMC.
>>> + * - ERROR_STATE. BMC has detected a protocol violation at the 
>>> interface level,
>>> + *                or the transfer has been aborted. System software 
>>> can either
>>> + *                use the "Get_Status" control code to request the 
>>> nature of
>>> + *                the error, or it can just retry the command.
>>> + */
>>> +#define KCS_IDLE_STATE           0
>>> +#define KCS_READ_STATE           1
>>> +#define KCS_WRITE_STATE          2
>>> +#define KCS_ERROR_STATE          3
>>> +
>>> +/* KCS Error Codes */
>>> +#define KCS_NO_ERROR                0x00
>>> +#define KCS_ABORTED_BY_COMMAND      0x01
>>> +#define KCS_ILLEGAL_CONTROL_CODE    0x02
>>> +#define KCS_LENGTH_ERROR            0x06
>>> +#define KCS_UNSPECIFIED_ERROR       0xFF
>>> +
>>> +
>>> +#define KCS_ZERO_DATA           0
>>> +
>>> +/* IPMI 2.0 - Table 9-1, KCS Interface Status Register Bits */
>>> +#define KCS_STR_STATE(state)        (state << 6)
>>> +#define KCS_STR_STATE_MASK          KCS_STR_STATE(0x3)
>>> +#define KCS_STR_CMD_DAT             BIT(3)
>>> +#define KCS_STR_SMS_ATN             BIT(2)
>>> +#define KCS_STR_IBF                 BIT(1)
>>> +#define KCS_STR_OBF                 BIT(0)
>>> +
>>> +
>>> +/* mapped to lpc-bmc@0 IO space */
>>> +#define LPC_HICR0            0x000
>>> +#define     LPC_HICR0_LPC3E          BIT(7)
>>> +#define     LPC_HICR0_LPC2E          BIT(6)
>>> +#define     LPC_HICR0_LPC1E          BIT(5)
>>> +#define LPC_HICR2            0x008
>>> +#define     LPC_HICR2_IBFIF3         BIT(3)
>>> +#define     LPC_HICR2_IBFIF2         BIT(2)
>>> +#define     LPC_HICR2_IBFIF1         BIT(1)
>>> +#define LPC_HICR4            0x010
>>> +#define     LPC_HICR4_LADR12AS       BIT(7)
>>> +#define     LPC_HICR4_KCSENBL        BIT(2)
>>> +#define LPC_LADR3H           0x014
>>> +#define LPC_LADR3L           0x018
>>> +#define LPC_LADR12H          0x01C
>>> +#define LPC_LADR12L          0x020
>>> +#define LPC_IDR1             0x024
>>> +#define LPC_IDR2             0x028
>>> +#define LPC_IDR3             0x02C
>>> +#define LPC_ODR1             0x030
>>> +#define LPC_ODR2             0x034
>>> +#define LPC_ODR3             0x038
>>> +#define LPC_STR1             0x03C
>>> +#define LPC_STR2             0x040
>>> +#define LPC_STR3             0x044
>>> +
>>> +/* mapped to lpc-host@80 IO space */
>>> +#define LPC_HICRB            0x080
>>> +#define     LPC_HICRB_IBFIF4         BIT(1)
>>> +#define     LPC_HICRB_LPC4E          BIT(0)
>>> +#define LPC_LADR4            0x090
>>> +#define LPC_IDR4             0x094
>>> +#define LPC_ODR4             0x098
>>> +#define LPC_STR4             0x09C
>>> +
>>> +
>>> +/* IPMI 2.0 - 9.5, KCS Interface Registers */
>>> +struct kcs_ioreg {
>>> +    u32 idr; /* Input Data Register */
>>> +    u32 odr; /* Output Data Register */
>>> +    u32 str; /* Status Register */
>>> +};
>>> +
>>> +static const struct kcs_ioreg kcs_ioreg_map[KCS_CHANNEL_MAX] = {
>>> +    { .idr = LPC_IDR1, .odr = LPC_ODR1, .str = LPC_STR1 },
>>> +    { .idr = LPC_IDR2, .odr = LPC_ODR2, .str = LPC_STR2 },
>>> +    { .idr = LPC_IDR3, .odr = LPC_ODR3, .str = LPC_STR3 },
>>> +    { .idr = LPC_IDR4, .odr = LPC_ODR4, .str = LPC_STR4 },
>>> +};
>
> One more thing...  Why aren't the above values being set in the device 
> tree?
> Passing in a channel (and address) seems inflexible.  Kind of goes 
> against the
> philosophy of device trees.
>
> -corey
>
Change it by referring to Joel's suggestion, and defining IDR/ODR/STR 
registers together with other
registers for LPC KCS, looks like this made code be more easily maintained.

https://lists.ozlabs.org/pipermail/openbmc/2017-December/010095.html

>>>
>>> +
>>> +struct kcs_bmc {
>>> +    struct regmap *map;
>>> +    spinlock_t     lock;
>>
>> This lock is only used in threads, as far as I can tell. Couldn't it 
>> just be a normal mutex?
>> But more on this later.
>>
I missed this lock using in KCS ISR function, for AST2500 is single core 
CPU. The critical data such as
data_in_avail is shared between ISR and user thread, spinlock_t related 
API should be the right one ?
especially for SMP ?

static irqreturn_t kcs_bmc_irq(int irq, void *arg)
{
     ....
     spin_lock(&kcs_bmc->lock);  // <-- MISSED

     switch (sts) {
     case KCS_STR_IBF | KCS_STR_CMD_DAT:
         kcs_rx_cmd(kcs_bmc);
         break;

     case KCS_STR_IBF:
         kcs_rx_data(kcs_bmc);
         break;

     default:
         ret = IRQ_NONE;
         break;
     }

     spin_unlock(&kcs_bmc->lock); // <-- MISSED

     return ret;
}


>>> +
>>> +    u32 chan;
>>> +    int running;
>>> +
>>> +    u32 idr;
>>> +    u32 odr;
>>> +    u32 str;
>>> +
>>> +    int kcs_phase;
>>> +    u8  abort_phase;
>>> +    u8  kcs_error;
>>> +
>>> +    wait_queue_head_t queue;
>>> +    int  data_in_avail;
>>
>> data_in_avail should be a bool.
>>
>> You set data_in_avail after the data is ready, but you don't have a 
>> barrier.  You
>> have similar problems with kcs_phase.
>>
>> In fact, the locking in the driver doesn't seem quite correct. If 
>> this ever ran on
>> an SMP system, it is likely to not work correctly.  You can assume 
>> that the interrupt
>> runs exclusively, but you cannot assume that the data operations are 
>> available in
>> order on another processor that handles a subsequent interrupt.
>>
>> The easiest way to fix this would be to add the spin lock around the 
>> case statement
>> in the irq handler and add them in the poll and read functions (you 
>> would need to
>> leave it as a spinlock in that case).  That would provide the proper 
>> barriers assuming
>> you put them in the right place (checking data_in_avail again inside 
>> the spinlock
>> in the read case, for instance).
>>
Got it!
>>> +    int  data_in_idx;
>>> +    u8  *data_in;
>>> +
>>> +    int  data_out_idx;
>>> +    int  data_out_len;
>>> +    u8  *data_out;
>>> +
>>> +    struct miscdevice miscdev;
>>> +};
>>> +
>>> +static u8 kcs_inb(struct kcs_bmc *kcs_bmc, u32 reg)
>>> +{
>>> +    u32 val = 0;
>>> +    int rc;
>>> +
>>> +    rc = regmap_read(kcs_bmc->map, reg, &val);
>>> +    WARN(rc != 0, "regmap_read() failed: %d\n", rc);
>>> +
>>> +    return rc == 0 ? (u8) val : 0;
>>> +}
>>> +
>>> +static void kcs_outb(struct kcs_bmc *kcs_bmc, u8 data, u32 reg)
>>> +{
>>> +    int rc;
>>> +
>>> +    rc = regmap_write(kcs_bmc->map, reg, data);
>>> +    WARN(rc != 0, "regmap_write() failed: %d\n", rc);
>>> +}
>>> +
>>> +static inline void kcs_set_state(struct kcs_bmc *kcs_bmc, u8 state)
>>> +{
>>> +    regmap_update_bits(kcs_bmc->map, kcs_bmc->str, KCS_STR_STATE_MASK,
>>> +            KCS_STR_STATE(state));
>>> +}
>>> +
>>> +static inline void kcs_set_atn(struct kcs_bmc *kcs_bmc)
>>> +{
>>> +    regmap_update_bits(kcs_bmc->map, kcs_bmc->str, KCS_STR_SMS_ATN,
>>> +            KCS_STR_SMS_ATN);
>>> +}
>>> +
>>> +static inline void kcs_clear_atn(struct kcs_bmc *kcs_bmc)
>>> +{
>>> +    regmap_update_bits(kcs_bmc->map, kcs_bmc->str, KCS_STR_SMS_ATN,
>>> +            0);
>>> +}
>>> +
>>> +/*
>>> + * AST_usrGuide_KCS.pdf
>>> + * 2. Background:
>>> + *   we note D for Data, and C for Cmd/Status, default rules are
>>> + *     A. KCS1 / KCS2 ( D / C:X / X+4 )
>>> + *        D / C : CA0h / CA4h
>>> + *        D / C : CA8h / CACh
>>> + *     B. KCS3 ( D / C:XX2h / XX3h )
>>> + *        D / C : CA2h / CA3h
>>> + *        D / C : CB2h / CB3h
>>> + *     C. KCS4
>>> + *        D / C : CA4h / CA5h
>>> + */
>>> +static void kcs_set_addr(struct kcs_bmc *kcs_bmc, u16 addr)
>>> +{
>>> +    switch (kcs_bmc->chan) {
>>> +    case 1:
>>> +        regmap_update_bits(kcs_bmc->map, LPC_HICR4,
>>> +                LPC_HICR4_LADR12AS, 0);
>>> +        regmap_write(kcs_bmc->map, LPC_LADR12H, addr >> 8);
>>> +        regmap_write(kcs_bmc->map, LPC_LADR12L, addr & 0xFF);
>>> +        break;
>>> +
>>> +    case 2:
>>> +        regmap_update_bits(kcs_bmc->map, LPC_HICR4,
>>> +                LPC_HICR4_LADR12AS, LPC_HICR4_LADR12AS);
>>> +        regmap_write(kcs_bmc->map, LPC_LADR12H, addr >> 8);
>>> +        regmap_write(kcs_bmc->map, LPC_LADR12L, addr & 0xFF);
>>> +        break;
>>> +
>>> +    case 3:
>>> +        regmap_write(kcs_bmc->map, LPC_LADR3H, addr >> 8);
>>> +        regmap_write(kcs_bmc->map, LPC_LADR3L, addr & 0xFF);
>>> +        break;
>>> +
>>> +    case 4:
>>> +        regmap_write(kcs_bmc->map, LPC_LADR4, ((addr + 1) << 16) |
>>> +            addr);
>>> +        break;
>>> +
>>> +    default:
>>
>> Shouldn't you return an error here?
>>
For I checked the channel number on kcs_bmc_probe, still need this kind 
of error handling ?

     rc = of_property_read_u32(dev->of_node, "kcs_chan", &chan);
     if ((rc != 0) || (chan == 0 || chan > KCS_CHANNEL_MAX)) {
         dev_err(dev, "no valid 'kcs_chan' configured\n");
         return -ENODEV;
     }

>>> +        break;
>>> +    }
>>> +}
>>> +
>>> +static void kcs_enable_channel(struct kcs_bmc *kcs_bmc, int enable)
>>> +{
>>> +    switch (kcs_bmc->chan) {
>>> +    case 1:
>>> +        if (enable) {
>>> +            regmap_update_bits(kcs_bmc->map, LPC_HICR2,
>>> +                    LPC_HICR2_IBFIF1, LPC_HICR2_IBFIF1);
>>> +            regmap_update_bits(kcs_bmc->map, LPC_HICR0,
>>> +                    LPC_HICR0_LPC1E, LPC_HICR0_LPC1E);
>>> +        } else {
>>> +            regmap_update_bits(kcs_bmc->map, LPC_HICR0,
>>> +                    LPC_HICR0_LPC1E, 0);
>>> +            regmap_update_bits(kcs_bmc->map, LPC_HICR2,
>>> +                    LPC_HICR2_IBFIF1, 0);
>>> +        }
>>> +        break;
>>> +
>>> +    case 2:
>>> +        if (enable) {
>>> +            regmap_update_bits(kcs_bmc->map, LPC_HICR2,
>>> +                    LPC_HICR2_IBFIF2, LPC_HICR2_IBFIF2);
>>> +            regmap_update_bits(kcs_bmc->map, LPC_HICR0,
>>> +                    LPC_HICR0_LPC2E, LPC_HICR0_LPC2E);
>>> +        } else {
>>> +            regmap_update_bits(kcs_bmc->map, LPC_HICR0,
>>> +                    LPC_HICR0_LPC2E, 0);
>>> +            regmap_update_bits(kcs_bmc->map, LPC_HICR2,
>>> +                    LPC_HICR2_IBFIF2, 0);
>>> +        }
>>> +        break;
>>> +
>>> +    case 3:
>>> +        if (enable) {
>>> +            regmap_update_bits(kcs_bmc->map, LPC_HICR2,
>>> +                    LPC_HICR2_IBFIF3, LPC_HICR2_IBFIF3);
>>> +            regmap_update_bits(kcs_bmc->map, LPC_HICR0,
>>> +                    LPC_HICR0_LPC3E, LPC_HICR0_LPC3E);
>>> +            regmap_update_bits(kcs_bmc->map, LPC_HICR4,
>>> +                    LPC_HICR4_KCSENBL, LPC_HICR4_KCSENBL);
>>> +        } else {
>>> +            regmap_update_bits(kcs_bmc->map, LPC_HICR0,
>>> +                    LPC_HICR0_LPC3E, 0);
>>> +            regmap_update_bits(kcs_bmc->map, LPC_HICR4,
>>> +                    LPC_HICR4_KCSENBL, 0);
>>> +            regmap_update_bits(kcs_bmc->map, LPC_HICR2,
>>> +                    LPC_HICR2_IBFIF3, 0);
>>> +        }
>>> +        break;
>>> +
>>> +    case 4:
>>> +        if (enable) {
>>> +            regmap_update_bits(kcs_bmc->map, LPC_HICRB,
>>> +                    LPC_HICRB_IBFIF4 | LPC_HICRB_LPC4E,
>>> +                    LPC_HICRB_IBFIF4 | LPC_HICRB_LPC4E);
>>> +        } else {
>>> +            regmap_update_bits(kcs_bmc->map, LPC_HICRB,
>>> +                    LPC_HICRB_IBFIF4 | LPC_HICRB_LPC4E,
>>> +                    0);
>>> +        }
>>
>> The above shouldn't have {}, did you run this through checkpatch?
Yes, I run the checkpatch, no this warning. ;-) But well, I will remove 
the '{}'.
>>
>>> +        break;
>>> +
>>> +    default:
>>
>> Error here, too?
>>
For I checked the channel number on kcs_bmc_probe, still need this kind 
of error handling ?
>>> +        break;
>>> +    }
>>> +}
>>> +
>>> +static void kcs_rx_data(struct kcs_bmc *kcs_bmc)
>>> +{
>>> +    u8 data;
>>> +
>>> +    switch (kcs_bmc->kcs_phase) {
>>> +    case KCS_PHASE_WRITE:
>>> +        kcs_set_state(kcs_bmc, KCS_WRITE_STATE);
>>> +
>>> +        /* set OBF before reading data */
>>> +        kcs_outb(kcs_bmc, KCS_ZERO_DATA, kcs_bmc->odr);
>>> +
>>> +        if (kcs_bmc->data_in_idx < KCS_MSG_BUFSIZ)
>>> +            kcs_bmc->data_in[kcs_bmc->data_in_idx++] =
>>> +                    kcs_inb(kcs_bmc, kcs_bmc->idr);
>>> +        break;
>>> +
>>> +    case KCS_PHASE_WRITE_END:
>>> +        kcs_set_state(kcs_bmc, KCS_READ_STATE);
>>> +
>>> +        if (kcs_bmc->data_in_idx < KCS_MSG_BUFSIZ)
>>> +            kcs_bmc->data_in[kcs_bmc->data_in_idx++] =
>>> +                    kcs_inb(kcs_bmc, kcs_bmc->idr);
>>> +
>>> +        kcs_bmc->kcs_phase = KCS_PHASE_READ;
>>> +        if (kcs_bmc->running) {
>>> +            kcs_bmc->data_in_avail = 1;
>>> +            wake_up_interruptible(&kcs_bmc->queue);
>>> +        }
>>> +        break;
>>> +
>>> +    case KCS_PHASE_READ:
>>> +        if (kcs_bmc->data_out_idx == kcs_bmc->data_out_len)
>>> +            kcs_set_state(kcs_bmc, KCS_IDLE_STATE);
>>> +
>>> +        data = kcs_inb(kcs_bmc, kcs_bmc->idr);
>>> +        if (data != KCS_READ_BYTE) {
>>> +            kcs_set_state(kcs_bmc, KCS_ERROR_STATE);
>>> +            kcs_outb(kcs_bmc, KCS_ZERO_DATA, kcs_bmc->odr);
>>> +            break;
>>> +        }
>>> +
>>> +        if (kcs_bmc->data_out_idx == kcs_bmc->data_out_len) {
>>> +            kcs_outb(kcs_bmc, KCS_ZERO_DATA, kcs_bmc->odr);
>>> +            kcs_bmc->kcs_phase = KCS_PHASE_IDLE;
>>> +            break;
>>> +        }
>>> +
>>> +        kcs_outb(kcs_bmc, kcs_bmc->data_out[kcs_bmc->data_out_idx++],
>>> +                 kcs_bmc->odr);
>>> +        break;
>>> +
>>> +    case KCS_PHASE_ABORT:
>>> +        switch (kcs_bmc->abort_phase) {
>>> +        case ABORT_PHASE_ERROR1:
>>> +            kcs_set_state(kcs_bmc, KCS_READ_STATE);
>>> +
>>> +            /* Read the Dummy byte */
>>> +            kcs_inb(kcs_bmc, kcs_bmc->idr);
>>> +
>>> +            kcs_outb(kcs_bmc, kcs_bmc->kcs_error, kcs_bmc->odr);
>>> +            kcs_bmc->abort_phase = ABORT_PHASE_ERROR2;
>>> +            break;
>>> +
>>> +        case ABORT_PHASE_ERROR2:
>>> +            kcs_set_state(kcs_bmc, KCS_IDLE_STATE);
>>> +
>>> +            /* Read the Dummy byte */
>>> +            kcs_inb(kcs_bmc, kcs_bmc->idr);
>>> +
>>> +            kcs_outb(kcs_bmc, KCS_ZERO_DATA, kcs_bmc->odr);
>>> +            kcs_bmc->kcs_phase = KCS_PHASE_IDLE;
>>> +            kcs_bmc->abort_phase = 0;
>>> +            break;
>>> +
>>> +        default:
>>> +            break;
>>> +        }
>>> +
>>> +        break;
>>> +
>>> +    case KCS_PHASE_ERROR:
>>
>> This is identical to the default.  And the default should never 
>> happen, anyway.
>> If the default happens you have a software bug and need to report it.
>>
For making code clean, I removed the KCS_PHASE_ERROR, just keep the 
'default' handling.
>>> +        kcs_set_state(kcs_bmc, KCS_ERROR_STATE);
>>> +
>>> +        /* Read the Dummy byte */
>>> +        kcs_inb(kcs_bmc, kcs_bmc->idr);
>>> +
>>> +        kcs_outb(kcs_bmc, KCS_ZERO_DATA, kcs_bmc->odr);
>>> +        break;
>>> +
>>> +    default:
>>> +        kcs_set_state(kcs_bmc, KCS_ERROR_STATE);
>>> +
>>> +        /* Read the Dummy byte */
>>> +        kcs_inb(kcs_bmc, kcs_bmc->idr);
>>> +
>>> +        kcs_outb(kcs_bmc, KCS_ZERO_DATA, kcs_bmc->odr);
>>> +        break;
>>> +    }
>>> +}
>>> +
>>> +static void kcs_rx_cmd(struct kcs_bmc *kcs_bmc)
>>> +{
>>> +    u8 cmd;
>>> +
>>> +    kcs_set_state(kcs_bmc, KCS_WRITE_STATE);
>>> +
>>> +    /* Dummy data to generate OBF */
>>> +    kcs_outb(kcs_bmc, KCS_ZERO_DATA, kcs_bmc->odr);
>>> +
>>> +    cmd = kcs_inb(kcs_bmc, kcs_bmc->idr);
>>
>> Wouldn't you want to read the command before you write the OBF?
>>
The host SMS KCS state is : 'wait for IBF=0' --> 'wait for OBF=1' /  
'clear OBF', for racing
condition, BMC needs prepare OBF=1, then clear IBF. ;-)
>>> +    switch (cmd) {
>>> +    case KCS_WRITE_START:
>>> +        kcs_bmc->data_in_avail = 0;
>>> +        kcs_bmc->data_in_idx   = 0;
>>> +        kcs_bmc->kcs_phase     = KCS_PHASE_WRITE;
>>> +        kcs_bmc->kcs_error     = KCS_NO_ERROR;
>>> +        break;
>>> +
>>> +    case KCS_WRITE_END:
>>> +        kcs_bmc->kcs_phase = KCS_PHASE_WRITE_END;
>>> +        break;
>>> +
>>> +    case KCS_ABORT:
>>> +        if (kcs_bmc->kcs_error == KCS_NO_ERROR)
>>> +            kcs_bmc->kcs_error = KCS_ABORTED_BY_COMMAND;
>>> +
>>> +        kcs_bmc->kcs_phase   = KCS_PHASE_ABORT;
>>> +        kcs_bmc->abort_phase = ABORT_PHASE_ERROR1;
>>> +        break;
>>> +
>>> +    default:
>>> +        kcs_bmc->kcs_error = KCS_ILLEGAL_CONTROL_CODE;
>>> +        kcs_set_state(kcs_bmc, KCS_ERROR_STATE);
>>> +        kcs_outb(kcs_bmc, kcs_bmc->kcs_error, kcs_bmc->odr);
>>> +        kcs_bmc->kcs_phase = KCS_PHASE_ERROR;
>>> +        break;
>>> +    }
>>> +}
>>> +
>>> +/*
>>> + * Whenever the BMC is reset (from power-on or a hard reset), the 
>>> State Bits
>>> + * are initialized to "11 - Error State". Doing so allows SMS to 
>>> detect that
>>> + * the BMC has been reset and that any message in process has been 
>>> terminated
>>> + * by the BMC.
>>> + */
>>> +static void kcs_force_abort(struct kcs_bmc *kcs_bmc)
>>> +{
>>> +    unsigned long flags;
>>> +
>>> +    spin_lock_irqsave(&kcs_bmc->lock, flags);
>>> +    kcs_set_state(kcs_bmc, KCS_ERROR_STATE);
>>> +
>>> +    /* Read the Dummy byte */
>>> +    kcs_inb(kcs_bmc, kcs_bmc->idr);
>>> +
>>> +    kcs_outb(kcs_bmc, KCS_ZERO_DATA, kcs_bmc->odr);
>>> +    kcs_bmc->kcs_phase = KCS_PHASE_ERROR;
>>> +    spin_unlock_irqrestore(&kcs_bmc->lock, flags);
>>
>> You don't set data_in_avail() to zero here?
>>
Done, added it.
>>> +}
>>> +
>>> +static irqreturn_t kcs_bmc_irq(int irq, void *arg)
>>> +{
>>> +    struct kcs_bmc *kcs_bmc = arg;
>>> +    u32 sts;
>>> +
>>> +    if (regmap_read(kcs_bmc->map, kcs_bmc->str, &sts) != 0)
>>> +        return IRQ_NONE;
>>> +
>>> +    sts &= (KCS_STR_IBF | KCS_STR_CMD_DAT);
>>> +
>>> +    switch (sts) {
>>> +    case KCS_STR_IBF | KCS_STR_CMD_DAT:
>>> +        kcs_rx_cmd(kcs_bmc);
>>> +        break;
>>> +
>>> +    case KCS_STR_IBF:
>>> +        kcs_rx_data(kcs_bmc);
>>> +
>>> +    default:
>>> +        return IRQ_NONE;
>>> +    }
>>> +
>>> +    return IRQ_HANDLED;
>>> +}
>>> +
>>> +static int kcs_bmc_config_irq(struct kcs_bmc *kcs_bmc,
>>> +            struct platform_device *pdev)
>>> +{
>>> +    struct device *dev = &pdev->dev;
>>> +    int irq;
>>> +
>>> +    irq = platform_get_irq(pdev, 0);
>>> +    if (irq < 0)
>>> +        return irq;
>>> +
>>> +    return devm_request_irq(dev, irq, kcs_bmc_irq, IRQF_SHARED,
>>> +            dev_name(dev), kcs_bmc);
>>> +}
>>> +
>>> +
>>> +static inline struct kcs_bmc *file_kcs_bmc(struct file *filp)
>>> +{
>>> +    return container_of(filp->private_data, struct kcs_bmc, miscdev);
>>> +}
>>> +
>>> +static int kcs_bmc_open(struct inode *inode, struct file *filp)
>>> +{
>>> +    struct kcs_bmc *kcs_bmc = file_kcs_bmc(filp);
>>> +    unsigned long flags;
>>> +
>>> +    if (kcs_bmc->running)
>>> +        return -EBUSY;
>>> +
>>
>> The above is a race, it needs to be done inside the lock.
>>
Fixed!
>>> + spin_lock_irqsave(&kcs_bmc->lock, flags);
>>> +    kcs_bmc->kcs_phase     = KCS_PHASE_IDLE;
>>> +    kcs_bmc->running       = 1;
>>> +    kcs_bmc->data_in_avail = 0;
>>> +    spin_unlock_irqrestore(&kcs_bmc->lock, flags);
>>
>> What happens if the interface is not in a state where it can send a 
>> message?
>> The release code doesn't block until anything is done, so the 
>> interface might
>> not be in a place where you can use it.  I think the init code 
>> handles it from
>> that side, but the release side is not handled.
>>
>> Also, if release gets called, wouldn't you want to call 
>> kcs_force_abort() here
>> or in release()? That would be the equivalent of the BMC getting reset.
>>
Yes, you are right. We meet this kind of bug that host is waiting BMC 
after it resets. So normally,
after the user ipmi stack is ready, it will call 
KCS_BMC_IOCTL_FORCE_ABORT, then the SMS can
get a right response.
>>> +
>>> +    return 0;
>>> +}
>>> +
>>> +static unsigned int kcs_bmc_poll(struct file *filp, poll_table *wait)
>>> +{
>>> +    struct kcs_bmc *kcs_bmc = file_kcs_bmc(filp);
>>> +    unsigned int mask = 0;
>>> +
>>> +    poll_wait(filp, &kcs_bmc->queue, wait);
>>> +
>>> +    if (kcs_bmc->data_in_avail)
>>> +        mask |= POLLIN;
>>> +
>>> +    if (kcs_bmc->kcs_phase == KCS_PHASE_READ)
>>> +        mask |= POLLOUT;
>>> +
>>> +    return mask;
>>> +}
>>> +
>>> +static ssize_t kcs_bmc_read(struct file *filp, char *buf,
>>> +                size_t count, loff_t *offset)
>>> +{
>>> +    struct kcs_bmc *kcs_bmc = file_kcs_bmc(filp);
>>> +    int rv;
>>> +
>>
>> You probably ought to handle O_NONBLOCK here.  (Same problem on BT, 
>> too.)
>>
Got it, will add this.
>>> +    rv = wait_event_interruptible(kcs_bmc->queue,
>>> +                kcs_bmc->data_in_avail != 0);
>>> +    if (rv < 0)
>>> +        return -ERESTARTSYS;
>>> +
>>
>> This is a race condition for multiple users.
>>
Got it, will fix this.
>>> +    kcs_bmc->data_in_avail = 0;
>>> +
>>> +    if (count > kcs_bmc->data_in_idx)
>>> +        count = kcs_bmc->data_in_idx;
>>> +
>>> +    if (copy_to_user(buf, kcs_bmc->data_in, count))
>>> +        return -EFAULT;
>>> +
>>> +    return count;
>>> +}
>>> +
>>> +static ssize_t kcs_bmc_write(struct file *filp, const char *buf,
>>> +                 size_t count, loff_t *offset)
>>> +{
>>> +    struct kcs_bmc *kcs_bmc = file_kcs_bmc(filp);
>>> +    unsigned long flags;
>>> +
>>> +    if (count < 1 || count > KCS_MSG_BUFSIZ)
>>> +        return -EINVAL;
>>> +
>>> +    if (copy_from_user(kcs_bmc->data_out, buf, count))
>>> +        return -EFAULT;
>>> +
>>> +    spin_lock_irqsave(&kcs_bmc->lock, flags);
>>> +    if (kcs_bmc->kcs_phase == KCS_PHASE_READ) {
>>
>> If you don't modify kcs_phase here, you have a race condition. You 
>> probably
>> need a KCS_WAIT_READ condition.  Also, the nomenclature of "read" and 
>> "write"
>> here is a little confusing, since your phases are from the host's 
>> point of view,
>> not this driver's point of view.  You might want to document that 
>> explicitly.
>>
The race condition means that the user MAY write the duplicated response ?
Will write some comments for these phase definition.
>>> +        kcs_bmc->data_out_idx = 1;
>>> +        kcs_bmc->data_out_len = count;
>>> +        kcs_outb(kcs_bmc, kcs_bmc->data_out[0], kcs_bmc->odr);
>>> +    }
>>
>> So if you write and the data isn't ready, you just drop the data on 
>> the floor silently?
>> Probably not the best design.  You should probably return an error, 
>> as write can
>> only be called after read.
>>
Yes, you are right, will return the right error code instead. ;-)
>>> + spin_unlock_irqrestore(&kcs_bmc->lock, flags);
>>> +
>>> +    return count;
>>> +}
>>> +
>>> +static long kcs_bmc_ioctl(struct file *filp, unsigned int cmd,
>>> +              unsigned long arg)
>>> +{
>>> +    struct kcs_bmc *kcs_bmc = file_kcs_bmc(filp);
>>> +    long ret = 0;
>>> +
>>> +    switch (cmd) {
>>> +    case KCS_BMC_IOCTL_SET_ATN:
>>> +        kcs_set_atn(kcs_bmc);
>>> +        break;
>>> +
>>> +    case KCS_BMC_IOCTL_CLR_ATN:
>>> +        kcs_clear_atn(kcs_bmc);
>>> +        break;
>>> +
>>> +    case KCS_BMC_IOCTL_FORCE_ABORT:
>>> +        kcs_force_abort(kcs_bmc);
>>> +        break;
>>> +
>>> +    default:
>>> +        ret = -EINVAL;
>>> +        break;
>>> +    }
>>> +
>>> +    return ret;
>>> +}
>>> +
>>> +static int kcs_bmc_release(struct inode *inode, struct file *filp)
>>> +{
>>> +    struct kcs_bmc *kcs_bmc = file_kcs_bmc(filp);
>>> +    unsigned long flags;
>>> +
>>> +    spin_lock_irqsave(&kcs_bmc->lock, flags);
>>> +    kcs_bmc->running = 0;
>>> +    spin_unlock_irqrestore(&kcs_bmc->lock, flags);
>>> +
>>> +    return 0;
>>> +}
>>> +
>>> +static const struct file_operations kcs_bmc_fops = {
>>> +    .owner          = THIS_MODULE,
>>> +    .open           = kcs_bmc_open,
>>> +    .read           = kcs_bmc_read,
>>> +    .write          = kcs_bmc_write,
>>> +    .release        = kcs_bmc_release,
>>> +    .poll           = kcs_bmc_poll,
>>> +    .unlocked_ioctl = kcs_bmc_ioctl,
>>> +};
>>> +
>>> +static int kcs_bmc_probe(struct platform_device *pdev)
>>> +{
>>> +    struct device *dev = &pdev->dev;
>>> +    const struct kcs_ioreg *ioreg;
>>> +    struct kcs_bmc *kcs_bmc;
>>> +    u32 chan, addr;
>>> +    int rc;
>>> +
>>> +    kcs_bmc = devm_kzalloc(dev, sizeof(*kcs_bmc), GFP_KERNEL);
>>> +    if (!kcs_bmc)
>>> +        return -ENOMEM;
>>
>> Every error after this point will leak kcs_bmc.  I'd recommend a 
>> "goto out_err"
>> to handle this.
>>
It is 'devm_xxx' API, it will be released automatically by the dev 
framework. It also can auto-release
the irq, so that probe function can be designed clearly. This is the 
first time I know about this. ;-)
>>> +
>>> +    rc = of_property_read_u32(dev->of_node, "kcs_chan", &chan);
>>> +    if ((rc != 0) || (chan == 0 || chan > KCS_CHANNEL_MAX)) {
>>> +        dev_err(dev, "no valid 'kcs_chan' configured\n");
>>> +        return -ENODEV;
>>> +    }
>>> +
>>> +    rc = of_property_read_u32(dev->of_node, "kcs_addr", &addr);
>>> +    if (rc) {
>>> +        dev_err(dev, "no valid 'kcs_addr' configured\n");
>>> +        return -ENODEV;
>>> +    }
>>> +
>>> +    kcs_bmc->map = syscon_node_to_regmap(dev->parent->of_node);
>>> +    if (IS_ERR(kcs_bmc->map)) {
>>> +        dev_err(dev, "Couldn't get regmap\n");
>>> +        return -ENODEV;
>>> +    }
>>> +
>>> +    dev_set_name(dev, "ipmi-kcs%u", chan);
>>> +
>>> +    spin_lock_init(&kcs_bmc->lock);
>>> +    kcs_bmc->chan = chan;
>>
>> You need error checking on chan.
>>
Has been checked above : if ((rc != 0) || (chan == 0 || chan > 
KCS_CHANNEL_MAX)) {
>>> +
>>> +    ioreg = &kcs_ioreg_map[chan - 1];
>>> +    kcs_bmc->idr  = ioreg->idr;
>>> +    kcs_bmc->odr  = ioreg->odr;
>>> +    kcs_bmc->str  = ioreg->str;
>>> +
>>> +    init_waitqueue_head(&kcs_bmc->queue);
>>> +    kcs_bmc->data_in  = devm_kmalloc(dev, KCS_MSG_BUFSIZ, GFP_KERNEL);
>>> +    kcs_bmc->data_out = devm_kmalloc(dev, KCS_MSG_BUFSIZ, GFP_KERNEL);
>>> +    if (kcs_bmc->data_in == NULL || kcs_bmc->data_out == NULL) {
>>> +        dev_err(dev, "Failed to allocate data buffers\n");
>>
>> You will leak memory if you fail to allocate data_out but do allocate 
>> data_in.
>>
It is 'devm_xxx' API, it will be released automatically by the dev 
framework.;-)
>>> +        return -ENOMEM;
>>> +    }
>>> +
>>> +    kcs_bmc->miscdev.minor = MISC_DYNAMIC_MINOR;
>>> +    kcs_bmc->miscdev.name = dev_name(dev);
>>> +    kcs_bmc->miscdev.fops = &kcs_bmc_fops;
>>> +    rc = misc_register(&kcs_bmc->miscdev);
>>> +    if (rc) {
>>> +        dev_err(dev, "Unable to register device\n");
>>> +        return rc;
>>> +    }
>>
>> After you call misc_register something can open the device and use it.
>> You need to do that after everything is enabled.
>>
Got it, will change the code order.
>>> +
>>> +    kcs_set_addr(kcs_bmc, addr);
>>> +    kcs_enable_channel(kcs_bmc, 1);
>>> +
>>> +    rc = kcs_bmc_config_irq(kcs_bmc, pdev);
>>> +    if (rc) {
>>> +        misc_deregister(&kcs_bmc->miscdev);
>>> +        return rc;
>>> +    }
>>> +
>>> +    dev_set_drvdata(&pdev->dev, kcs_bmc);
>>
>> This  should definitely be before you enable or register.  The drvdata
>> needs to be available in case an irq comes in, for instance.
>>
Got it, will change the code order.
>>> +
>>> +    dev_info(dev, "addr=0x%x, idr=0x%x, odr=0x%x, str=0x%x\n",
>>> +        addr, kcs_bmc->idr, kcs_bmc->odr, kcs_bmc->str);
>>> +
>>> +    return 0;
>>> +}
>>> +
>>> +static int kcs_bmc_remove(struct platform_device *pdev)
>>> +{
>>> +    struct kcs_bmc *kcs_bmc = dev_get_drvdata(&pdev->dev);
>>> +
>>> +    misc_deregister(&kcs_bmc->miscdev);
>>> +
>>> +    return 0;
>>> +}
>>> +
>>> +static const struct of_device_id kcs_bmc_match[] = {
>>> +    { .compatible = "aspeed,ast2400-kcs-bmc" },
>>> +    { .compatible = "aspeed,ast2500-kcs-bmc" },
>>> +    { }
>>> +};
>>> +
>>> +static struct platform_driver kcs_bmc_driver = {
>>> +    .driver = {
>>> +        .name           = DEVICE_NAME,
>>> +        .of_match_table = kcs_bmc_match,
>>> +    },
>>> +    .probe = kcs_bmc_probe,
>>> +    .remove = kcs_bmc_remove,
>>> +};
>>> +
>>> +module_platform_driver(kcs_bmc_driver);
>>> +
>>> +MODULE_DEVICE_TABLE(of, kcs_bmc_match);
>>> +MODULE_LICENSE("GPL v2");
>>> +MODULE_AUTHOR("Haiyue Wang <haiyue.wang@linux.intel.com>");
>>> +MODULE_DESCRIPTION("Linux device interface to the IPMI KCS 
>>> interface");
>>> diff --git a/include/uapi/linux/kcs-bmc.h 
>>> b/include/uapi/linux/kcs-bmc.h
>>> new file mode 100644
>>> index 0000000..d1550d3
>>> --- /dev/null
>>> +++ b/include/uapi/linux/kcs-bmc.h
>>> @@ -0,0 +1,14 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +// Copyright (c) 2015-2018, Intel Corporation.
>>> +
>>> +#ifndef _UAPI_LINUX_KCS_BMC_H
>>> +#define _UAPI_LINUX_KCS_BMC_H
>>> +
>>> +#include <linux/ioctl.h>
>>> +
>>> +#define __KCS_BMC_IOCTL_MAGIC        'K'
>>> +#define KCS_BMC_IOCTL_SET_ATN _IO(__KCS_BMC_IOCTL_MAGIC, 1)
>>> +#define KCS_BMC_IOCTL_CLR_ATN _IO(__KCS_BMC_IOCTL_MAGIC, 2)
>>> +#define KCS_BMC_IOCTL_FORCE_ABORT _IO(__KCS_BMC_IOCTL_MAGIC, 3)
>>> +
>>> +#endif /* _UAPI_LINUX_KCS_BMC_H */
>>
>>
>