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SubjectRe: [PATCH v2] PCI: mediatek-gen3: Disable DVFSRC voltage request
On Wed, Oct 13, 2021 at 01:35:17PM -0500, Bjorn Helgaas wrote:
> On Wed, Oct 13, 2021 at 03:53:28PM +0800, Jianjun Wang wrote:
> > When the DVFSRC feature is not implemented, the MAC layer will
> > assert a voltage request signal when exit from the L1ss state,
> > but cannot receive the voltage ready signal, which will cause
> > the link to fail to exit the L1ss state correctly.
> >
> > Disable DVFSRC voltage request by default, we need to find
> > a common way to enable it in the future.
>
> Rewrap commit log to fill 75 columns.
>
> Does "L1ss" above refer to L1.1 and L1.2? If so, please say that
> explicitly or say something like "L1 PM Substates" (the term used in
> the PCIe spec) so it's clear.
>
> This seems on the boundary of PCIe-specified things and Mediatek
> implementation details, so I'm not sure what "DVFSRC," "MAC," and
> "voltage request signal" mean. Since I don't recognize those terms,
> I'm guessing they are Mediatek-specific things.
>
> But if they are things specified by the PCIe spec, please use the
> exact names used in the spec.
>
> > Signed-off-by: Jianjun Wang <jianjun.wang@mediatek.com>
> > Reviewed-by: Tzung-Bi Shih <tzungbi@google.com>
> > Tested-by: Qizhong Cheng <qizhong.cheng@mediatek.com>

Krzysztof also pointed out that if this is a bug fix, we may want a
stable tag here. And, ideally, a Fixes: tag with the specific commit
that introduced the bug.

> > ---
> > drivers/pci/controller/pcie-mediatek-gen3.c | 8 ++++++++
> > 1 file changed, 8 insertions(+)
> >
> > diff --git a/drivers/pci/controller/pcie-mediatek-gen3.c b/drivers/pci/controller/pcie-mediatek-gen3.c
> > index f3aeb8d4eaca..79fb12fca6a9 100644
> > --- a/drivers/pci/controller/pcie-mediatek-gen3.c
> > +++ b/drivers/pci/controller/pcie-mediatek-gen3.c
> > @@ -79,6 +79,9 @@
> > #define PCIE_ICMD_PM_REG 0x198
> > #define PCIE_TURN_OFF_LINK BIT(4)
> >
> > +#define PCIE_MISC_CTRL_REG 0x348
> > +#define PCIE_DISABLE_DVFSRC_VLT_REQ BIT(1)
> > +
> > #define PCIE_TRANS_TABLE_BASE_REG 0x800
> > #define PCIE_ATR_SRC_ADDR_MSB_OFFSET 0x4
> > #define PCIE_ATR_TRSL_ADDR_LSB_OFFSET 0x8
> > @@ -297,6 +300,11 @@ static int mtk_pcie_startup_port(struct mtk_pcie_port *port)
> > val &= ~PCIE_INTX_ENABLE;
> > writel_relaxed(val, port->base + PCIE_INT_ENABLE_REG);
> >
> > + /* Disable DVFSRC voltage request */
> > + val = readl_relaxed(port->base + PCIE_MISC_CTRL_REG);
> > + val |= PCIE_DISABLE_DVFSRC_VLT_REQ;
> > + writel_relaxed(val, port->base + PCIE_MISC_CTRL_REG);
> > +
> > /* Assert all reset signals */
> > val = readl_relaxed(port->base + PCIE_RST_CTRL_REG);
> > val |= PCIE_MAC_RSTB | PCIE_PHY_RSTB | PCIE_BRG_RSTB | PCIE_PE_RSTB;
> > --
> > 2.25.1
> >

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