On 06/11/2018 03:59 PM, Bjorn Helgaas wrote:
> On Sun, Jun 10, 2018 at 03:57:10PM +0200, Marek Vasut wrote:
>> On 11/17/2017 06:49 PM, Lorenzo Pieralisi wrote:
>>> On Fri, Nov 10, 2017 at 10:58:42PM +0100, Marek Vasut wrote:
>>>> From: Phil Edworthy <phil.edworthy@xxxxxxxxxxx>
>>>>
>>>> Most PCIe host controllers support L0s and L1 power states via ASPM.
>>>> The R-Car hardware only supports L0s, so when the system suspends and
>>>> resumes we have to manually handle L1.
>>>> When the system suspends, cards can put themselves into L1 and send a
>>>
>>> I assumed L1 entry has to be negotiated depending upon the PCIe
>>> hierarchy capabilities, I would appreciate if you can explain to
>>> me what's the root cause of the issue please.
>>
>> You should probably ignore the suspend/resume part altogether. The issue
>> here is that the cards can enter L1 state, while the controller won't do
>> that automatically, it can only detect that the link went into L1 state.
>> If that happens,the driver must manually put the controller to L1 state.
>> The controller can transition out of L1 state automatically though.
>
> From earlier discussion I thought the R-Car root port did not
> advertise L1 support.
Which discussion ? This one or somewhere else ?
> If that's the case, we shouldn't enable L1
> entry on a card. Is the core ASPM code doing something wrong here?
I can double-check, am I looking for some particular register in the
PCIe space ?
>>>> PM_ENTER_L1 DLLP to the host controller. At this point, we can no longer
>>>> access the card's config registers.
>>>>
>>>> The R-Car host controller will handle taking cards out of L1 as long as
>>>> the host controller has also been transitioned to L1 link state.
>>>
>>> I wonder why this can't be done in a PM restore hook but that's not
>>> really where my question is.
>>
>> I suspect because the link can be in L1 during startup too?
>>
>>>> Ideally, we would detect the PM_ENTER_L1 DLLP using an interrupt and
>>>> transition the host to L1 immediately. However, this patch just ensures
>>>> that we can talk to cards after they have gone into L1.
>>>
>>>> When attempting a config access, it checks to see if the card has gone
>>>> into L1, and if so, does the same for the host controller.
>>>>
>>>> This is based on a patch by Hien Dang <hien.dang.eb@xxxxxxxxxxxxxxx>
>>>>
>>>> Signed-off-by: Phil Edworthy <phil.edworthy@xxxxxxxxxxx>
>>>> Signed-off-by: Marek Vasut <marek.vasut+renesas@xxxxxxxxx>
>>>> Cc: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
>>>> Cc: Phil Edworthy <phil.edworthy@xxxxxxxxxxx>
>>>> Cc: Simon Horman <horms+renesas@xxxxxxxxxxxx>
>>>> Cc: Wolfram Sang <wsa@xxxxxxxxxxxxx>
>>>> Cc: linux-renesas-soc@xxxxxxxxxxxxxxx
>>>> ---
>>>> V2: - Drop extra parenthesis
>>>> - Use GENMASK()
>>>> - Fix comment "The HW will handle coming of of L1.", s/of of/out of/
>>>> ---
>>>> drivers/pci/host/pcie-rcar.c | 24 ++++++++++++++++++++++++
>>>> 1 file changed, 24 insertions(+)
>>>>
>>>> diff --git a/drivers/pci/host/pcie-rcar.c b/drivers/pci/host/pcie-rcar.c
>>>> index ab61829db389..068bf9067ec1 100644
>>>> --- a/drivers/pci/host/pcie-rcar.c
>>>> +++ b/drivers/pci/host/pcie-rcar.c
>>>> @@ -92,6 +92,13 @@
>>>> #define MACCTLR 0x011058
>>>> #define SPEED_CHANGE BIT(24)
>>>> #define SCRAMBLE_DISABLE BIT(27)
>>>> +#define PMSR 0x01105c
>>>> +#define L1FAEG BIT(31)
>>>> +#define PM_ENTER_L1RX BIT(23)
>>>> +#define PMSTATE GENMASK(18, 16)
>>>> +#define PMSTATE_L1 GENMASK(17, 16)
>>>> +#define PMCTLR 0x011060
>>>> +#define L1_INIT BIT(31)
>>>> #define MACS2R 0x011078
>>>> #define MACCGSPSETR 0x011084
>>>> #define SPCNGRSN BIT(31)
>>>> @@ -191,6 +198,7 @@ static int rcar_pcie_config_access(struct rcar_pcie *pcie,
>>>> unsigned int devfn, int where, u32 *data)
>>>> {
>>>> int dev, func, reg, index;
>>>> + u32 val;
>>>>
>>>> dev = PCI_SLOT(devfn);
>>>> func = PCI_FUNC(devfn);
>>>> @@ -232,6 +240,22 @@ static int rcar_pcie_config_access(struct rcar_pcie *pcie,
>>>> if (pcie->root_bus_nr < 0)
>>>> return PCIBIOS_DEVICE_NOT_FOUND;
>>>>
>>>> + /*
>>>> + * If we are not in L1 link state and we have received PM_ENTER_L1 DLLP,
>>>> + * transition to L1 link state. The HW will handle coming out of L1.
>>>> + */
>>>> + val = rcar_pci_read_reg(pcie, PMSR);
>>>> + if (val & PM_ENTER_L1RX && (val & PMSTATE) != PMSTATE_L1) {
>>>> + rcar_pci_write_reg(pcie, L1_INIT, PMCTLR);
>>>> +
>>>> + /* Wait until we are in L1 */
>>>> + while (!(val & L1FAEG))
>>>> + val = rcar_pci_read_reg(pcie, PMSR);
>>>> +
>>>> + /* Clear flags indicating link has transitioned to L1 */
>>>> + rcar_pci_write_reg(pcie, L1FAEG | PM_ENTER_L1RX, PMSR);
>>>> + }
>>>
>>> I do not get why you need to add the DLLP check for _every_ given config
>>> access and how/why it is just related to suspend/resume and not eg cold
>>> boot (I supposed it is because devices can enter L1 upon suspend(?)), I
>>> would ask you please to provide a thorough explanation so that I can
>>> actually review this patch (the commit log must be rewritten nonetheless,
>>> I do not think it is clear, at least it is not for me).
>>
>> See above
>>
>> --
>> Best regards,
>> Marek Vasut
--
Best regards,
Marek Vasut
