Re: [PATCH V5 1/5] PCI: Add TLP Processing Hints (TPH) support

Alejandro Lucero Palau
2024-09-24T14:34:32Z

On 9/23/24 21:27, Wei Huang wrote:
>
>
> On 9/23/24 7:07 AM, Alejandro Lucero Palau wrote:
>>
>
> ...
>
>>> +/**
>>> + * pcie_enable_tph - Enable TPH support for device using a specific
>>> ST mode
>>> + * @pdev: PCI device
>>> + * @mode: ST mode to enable. Current supported modes include:
>>> + *
>>> + *   - PCI_TPH_ST_NS_MODE: NO ST Mode
>>> + *   - PCI_TPH_ST_IV_MODE: Interrupt Vector Mode
>>> + *   - PCI_TPH_ST_DS_MODE: Device Specific Mode
>>> + *
>>> + * Checks whether the mode is actually supported by the device
>>> before enabling
>>> + * and returns an error if not. Additionally determines what types
>>> of requests,
>>> + * TPH or extended TPH, can be issued by the device based on its
>>> TPH requester
>>> + * capability and the Root Port's completer capability.
>>> + *
>>> + * Return: 0 on success, otherwise negative value (-errno)
>>> + */
>>> +int pcie_enable_tph(struct pci_dev *pdev, int mode)
>>> +{
>>> +    u32 reg;
>>> +    u8 dev_modes;
>>> +    u8 rp_req_type;
>>> +
>>> +    /* Honor "notph" kernel parameter */
>>> +    if (pci_tph_disabled)
>>> +        return -EINVAL;
>>> +
>>> +    if (!pdev->tph_cap)
>>> +        return -EINVAL;
>>> +
>>> +    if (pdev->tph_enabled)
>>> +        return -EBUSY;
>>> +
>>> +    /* Sanitize and check ST mode comptability */
>>> +    mode &= PCI_TPH_CTRL_MODE_SEL_MASK;
>>> +    dev_modes = get_st_modes(pdev);
>>> +    if (!((1 << mode) & dev_modes))
>>
>>
>> This is wrong. The mode definition is about the bit on and not about bit
>> position. You got this right in v4 ...
>
> This code is correct. In V5, I changed the "mode" parameter to the
> following values, as defined in TPH Ctrl register. These values are
> defined as bit positions:
>
> PCI_TPH_ST_NS_MODE: NO ST Mode
> PCI_TPH_ST_IV_MODE: Interrupt Vector Mode
> PCI_TPH_ST_DS_MODE: Device Specific Mode
>

OK. I found the issue. I was using PCI_TPH_CAP_ST_DS for the mode
instead of PCI_TPH_ST_DS_MODE.

That change confused me.

Apologies.

> In V4, "mode" is defined as masks of TPH Cap register. I felt that V5
> looks more straightforward:
>
> V4: pcie_enable_tph(dev, PCI_TPH_CAP_ST_IV)
> vs.
> V5: pcie_enable_tph(dev, PCI_TPH_ST_IV_MODE)
>
>>
>>
>>> +        return -EINVAL;
>