Hi Marek,
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.
> 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.
> 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).
Thanks,
Lorenzo
> +
> /* Clear errors */
> rcar_pci_write_reg(pcie, rcar_pci_read_reg(pcie, PCIEERRFR), PCIEERRFR);
>
> --
> 2.11.0
>
