Date: Thu, 18 Apr 2024 10:37:23 -0700
From: Mayank Rana <quic_mrana@...cinc.com>
To: Qiang Yu <quic_qianyu@...cinc.com>, <mani@...nel.org>,
        <quic_jhugo@...cinc.com>
CC: <mhi@...ts.linux.dev>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <quic_cang@...cinc.com>
Subject: Re: [PATCH v3 3/3] bus: mhi: host: pci_generic: Add edl callback to
 enter EDL



On 4/16/2024 9:41 PM, Qiang Yu wrote:
> 
> On 4/17/2024 11:01 AM, Qiang Yu wrote:
>>
>> On 4/17/2024 2:12 AM, Mayank Rana wrote:
>>>
>>>
>>> On 4/15/2024 8:50 PM, Qiang Yu wrote:
>>>>
>>>> On 4/16/2024 7:53 AM, Mayank Rana wrote:
>>>>> Hi Qiang
>>>>>
>>>>> On 4/15/2024 1:49 AM, Qiang Yu wrote:
>>>>>> Add mhi_pci_generic_edl_trigger as edl_trigger for some devices 
>>>>>> (eg. SDX65)
>>>>>> to enter EDL mode by writing the 0xEDEDEDED cookie to the channel 91
>>>>>> doorbell register and forcing an SOC reset afterwards.
>>>>>>
>>>>>> Signed-off-by: Qiang Yu <quic_qianyu@...cinc.com>
>>>>>> ---
>>>>>>   drivers/bus/mhi/host/pci_generic.c | 47 
>>>>>> ++++++++++++++++++++++++++++++++++++++
>>>>>>   1 file changed, 47 insertions(+)
>>>>>>
>>>>>> diff --git a/drivers/bus/mhi/host/pci_generic.c 
>>>>>> b/drivers/bus/mhi/host/pci_generic.c
>>>>>> index 51639bf..cbf8a58 100644
>>>>>> --- a/drivers/bus/mhi/host/pci_generic.c
>>>>>> +++ b/drivers/bus/mhi/host/pci_generic.c
>>>>>> @@ -27,12 +27,19 @@
>>>>>>   #define PCI_VENDOR_ID_THALES    0x1269
>>>>>>   #define PCI_VENDOR_ID_QUECTEL    0x1eac
>>>>>>   +#define MHI_EDL_DB            91
>>>>>> +#define MHI_EDL_COOKIE            0xEDEDEDED
>>>>>> +
>>>>>> +/* Device can enter EDL by first setting edl cookie then issuing 
>>>>>> inband reset*/
>>>>>> +#define MHI_PCI_GENERIC_EDL_TRIGGER    BIT(0)
>>>>>> +
>>>>>>   /**
>>>>>>    * struct mhi_pci_dev_info - MHI PCI device specific information
>>>>>>    * @config: MHI controller configuration
>>>>>>    * @name: name of the PCI module
>>>>>>    * @fw: firmware path (if any)
>>>>>>    * @edl: emergency download mode firmware path (if any)
>>>>>> + * @edl_trigger: each bit represents a different way to enter EDL
>>>>>>    * @bar_num: PCI base address register to use for MHI MMIO 
>>>>>> register space
>>>>>>    * @dma_data_width: DMA transfer word size (32 or 64 bits)
>>>>>>    * @mru_default: default MRU size for MBIM network packets
>>>>>> @@ -44,6 +51,7 @@ struct mhi_pci_dev_info {
>>>>>>       const char *name;
>>>>>>       const char *fw;
>>>>>>       const char *edl;
>>>>>> +    unsigned int edl_trigger;
>>>>>>       unsigned int bar_num;
>>>>>>       unsigned int dma_data_width;
>>>>>>       unsigned int mru_default;
>>>>>> @@ -292,6 +300,7 @@ static const struct mhi_pci_dev_info 
>>>>>> mhi_qcom_sdx75_info = {
>>>>>>       .name = "qcom-sdx75m",
>>>>>>       .fw = "qcom/sdx75m/xbl.elf",
>>>>>>       .edl = "qcom/sdx75m/edl.mbn",
>>>>>> +    .edl_trigger = MHI_PCI_GENERIC_EDL_TRIGGER,
>>>>>>       .config = &modem_qcom_v2_mhiv_config,
>>>>>>       .bar_num = MHI_PCI_DEFAULT_BAR_NUM,
>>>>>>       .dma_data_width = 32,
>>>>>> @@ -302,6 +311,7 @@ static const struct mhi_pci_dev_info 
>>>>>> mhi_qcom_sdx65_info = {
>>>>>>       .name = "qcom-sdx65m",
>>>>>>       .fw = "qcom/sdx65m/xbl.elf",
>>>>>>       .edl = "qcom/sdx65m/edl.mbn",
>>>>>> +    .edl_trigger = MHI_PCI_GENERIC_EDL_TRIGGER,
>>>>>>       .config = &modem_qcom_v1_mhiv_config,
>>>>>>       .bar_num = MHI_PCI_DEFAULT_BAR_NUM,
>>>>>>       .dma_data_width = 32,
>>>>>> @@ -312,6 +322,7 @@ static const struct mhi_pci_dev_info 
>>>>>> mhi_qcom_sdx55_info = {
>>>>>>       .name = "qcom-sdx55m",
>>>>>>       .fw = "qcom/sdx55m/sbl1.mbn",
>>>>>>       .edl = "qcom/sdx55m/edl.mbn",
>>>>>> +    .edl_trigger = MHI_PCI_GENERIC_EDL_TRIGGER,
>>>>>>       .config = &modem_qcom_v1_mhiv_config,
>>>>>>       .bar_num = MHI_PCI_DEFAULT_BAR_NUM,
>>>>>>       .dma_data_width = 32,
>>>>>> @@ -928,6 +939,39 @@ static void health_check(struct timer_list *t)
>>>>>>       mod_timer(&mhi_pdev->health_check_timer, jiffies + 
>>>>>> HEALTH_CHECK_PERIOD);
>>>>>>   }
>>>>>>   +static int mhi_pci_generic_edl_trigger(struct mhi_controller 
>>>>>> *mhi_cntrl)
>>>>>> +{
>>>>>> +    void __iomem *base = mhi_cntrl->regs;
>>>>>> +    void __iomem *edl_db;
>>>>>> +    int ret;
>>>>>> +    u32 val;
>>>>>> +
>>>>>> +    ret = mhi_device_get_sync(mhi_cntrl->mhi_dev);
>>>>>> +    if (ret) {
>>>>>> +        dev_err(mhi_cntrl->cntrl_dev, "Wake up device fail before 
>>>>>> trigger EDL\n");
>>>>>> +        return ret;
>>>>>> +    }
>>>>>> +
>>>>>> +    pm_wakeup_event(&mhi_cntrl->mhi_dev->dev, 0);
>>>>>> +    mhi_cntrl->runtime_get(mhi_cntrl);
>>>>>> +
>>>>>> +    ret = mhi_get_channel_doorbell(mhi_cntrl, &val);
>>>>>> +    if (ret)
>>>>>> +        return ret;
>>>>> Don't we need error handling part here i.e. calling 
>>>>> mhi_cntrl->runtime_put() as well mhi_device_put() ?
>>>>
>>>> Hi Mayank
>>>>
>>>> After soc_reset, device will reboot to EDL mode and MHI state will 
>>>> be SYSERR. So host will fail to suspend
>>>> anyway. The "error handling" we need here is actually to enter EDL 
>>>> mode, this will be done by SYSERR irq.
>>>> Here, mhi_cntrl->runtime_put() and mhi_device_put() are only to 
>>>> balance mhi_cntrl->runtime_get() and
>>>> mhi_device_get_sync().
>>>>
>>>> Thanks,
>>>> Qiang
>>> I am saying is there possibility that mhi_get_channel_doorbell() 
>>> returns error ?
>>> If yes, then why don't we need error handling as part of it. you are 
>>> exiting if this API return error without doing anything.
>>
>> I think here mhi_get_channel_doorbell will not return error. But I still
>> add a error checking because it invoked mhi_read_reg, which is a must 
>> check
>> API. For modem mhi controller, this API eventually does a memory read.
>> This memory read will return a normal value if link is up and all f's 
>> if link
>> is bad.
>>
>> Thanks,
>> Qiang
> 
> Actually, mhi_get_channel_doorbell should also be used in mhi_init_mmio to
> replace the getting chdb operation by invoking mhi_read_reg as Mani 
> commented.
> In mhi_init_mmio, we invoke mhi_read_reg many times, but there is also not
> additionnal error handling.
I don't see that any specific step required within this API i.e. doing undo
as it is just reading registers. so there is nothing else needed to be 
performed here as part of register read failure scenario.

> I'm not very sure the reason but perhaps if mhi_read_reg returns error 
> (I don't
> know which controller will provide a memory read callback returning 
> errors), most
> probably something is wrong in PCIe, which is not predictable by MHI and 
> we can
> not add err handling every time invoking mhi_read_reg. But we have a 
> timer to
> do health_check in pci_generic.c. If link is down, we will do 
> pci_function_reset
> to try to reovery.

There are more than 21 places in MHI host stack mhi_read_reg() API based 
error handling
is performed. With this new code addition, why it is supposed to be 
exception here. So these are possible options available here:
1. If you don't want to perform error handling, provide good inline 
comment here saying why you don't want to perform error handling.
2. Remove __must_check annotation with mhi_read_reg() and don't check 
return value here.
3. Other option is to check if device is not into M0, then just return 
without performing anything here.

Regards,
Mayank

> Hi Mani, sorry, may I know the purpose of adding must_check attribute to
> mhi_read_reg? In which case will mhi controller provide a callback that
> returns error?
> 
> Thanks,
> Qiang
>>>>>> +    edl_db = base + val + (8 * MHI_EDL_DB);
>>>>>> +
>>>>>> +    mhi_cntrl->write_reg(mhi_cntrl, edl_db + 4, 
>>>>>> upper_32_bits(MHI_EDL_COOKIE));
>>>>>> +    mhi_cntrl->write_reg(mhi_cntrl, edl_db, 
>>>>>> lower_32_bits(MHI_EDL_COOKIE));
>>>>>> +
>>>>>> +    mhi_soc_reset(mhi_cntrl);
>>>>>> +
>>>>>> +    mhi_cntrl->runtime_put(mhi_cntrl);
>>>>>> +    mhi_device_put(mhi_cntrl->mhi_dev);
>>>>>> +
>>>>>> +    return 0;
>>>>>> +}
>>>>>> +
>>>>>>   static int mhi_pci_probe(struct pci_dev *pdev, const struct 
>>>>>> pci_device_id *id)
>>>>>>   {
>>>>>>       const struct mhi_pci_dev_info *info = (struct 
>>>>>> mhi_pci_dev_info *) id->driver_data;
>>>>>> @@ -962,6 +1006,9 @@ static int mhi_pci_probe(struct pci_dev 
>>>>>> *pdev, const struct pci_device_id *id)
>>>>>>       mhi_cntrl->runtime_put = mhi_pci_runtime_put;
>>>>>>       mhi_cntrl->mru = info->mru_default;
>>>>>>   +    if (info->edl_trigger & MHI_PCI_GENERIC_EDL_TRIGGER)
>>>>>> +        mhi_cntrl->edl_trigger = mhi_pci_generic_edl_trigger;
>>>>>> +
>>>>>>       if (info->sideband_wake) {
>>>>>>           mhi_cntrl->wake_get = mhi_pci_wake_get_nop;
>>>>>>           mhi_cntrl->wake_put = mhi_pci_wake_put_nop;
>>>>> Regards,
>>>>> Mayank
>>

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