RE: [PATCH v2 1/7] reset: imx7: Add the iMX8MP PCIe PHY PERST support

[Hongxing Zhu]

Hi Philipp:

> -----Original Message-----
> From: Hongxing Zhu
> Sent: 2022年4月15日 15:33
> To: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>; l.stach@xxxxxxxxxxxxxx;
> bhelgaas@xxxxxxxxxx; lorenzo.pieralisi@xxxxxxx; robh@xxxxxxxxxx;
> shawnguo@xxxxxxxxxx; vkoul@xxxxxxxxxx; alexander.stein@xxxxxxxxxxxxxxx
> Cc: linux-phy@xxxxxxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx;
> linux-pci@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; kernel@xxxxxxxxxxxxxx; dl-linux-imx
> <linux-imx@xxxxxxx>
> Subject: RE: [PATCH v2 1/7] reset: imx7: Add the iMX8MP PCIe PHY PERST
> support
> 
> Hi Philipp:
> 
> > -----Original Message-----
> > From: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
> > Sent: 2022年4月4日 17:34
> > To: Hongxing Zhu <hongxing.zhu@xxxxxxx>; l.stach@xxxxxxxxxxxxxx;
> > bhelgaas@xxxxxxxxxx; lorenzo.pieralisi@xxxxxxx; robh@xxxxxxxxxx;
> > shawnguo@xxxxxxxxxx; vkoul@xxxxxxxxxx; alexander.stein@xxxxxxxxxxxxxxx
> > Cc: linux-phy@xxxxxxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx;
> > linux-pci@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> > linux-kernel@xxxxxxxxxxxxxxx; kernel@xxxxxxxxxxxxxx; dl-linux-imx
> > <linux-imx@xxxxxxx>
> > Subject: Re: [PATCH v2 1/7] reset: imx7: Add the iMX8MP PCIe PHY PERST
> > support
> >
> > Hi Richard,
> >
> > On Mo, 2022-03-07 at 17:07 +0800, Richard Zhu wrote:
> > > Add the i.MX8MP PCIe PHY PERST support.
> > >
> > > Signed-off-by: Richard Zhu <hongxing.zhu@xxxxxxx>
> > > ---
> > >  drivers/reset/reset-imx7.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > >
> > > diff --git a/drivers/reset/reset-imx7.c b/drivers/reset/reset-imx7.c
> > > index 185a333df66c..d2408725eb2c 100644
> > > --- a/drivers/reset/reset-imx7.c
> > > +++ b/drivers/reset/reset-imx7.c
> > > @@ -329,6 +329,7 @@ static int imx8mp_reset_set(struct
> > > reset_controller_dev *rcdev,
> > >                 break;
> > >
> > >         case IMX8MP_RESET_PCIE_CTRL_APPS_EN:
> > > +       case IMX8MP_RESET_PCIEPHY_PERST:
> > >                 value = assert ? 0 : bit;
> > >                 break;
> > >         }
> >
> > This doesn't do what the commit description says.
> >
> > The PCIEPHY_PERST bit is already supported by the driver (albeit
> > incorrectly?) - this patch just inverts the bit.
> >
> > Since this bit is not inverted on the other platforms, and the i.MX8MP
> > reference manual says nothing about this, please explicitly state why
> > this needs to be inverted and call it a fix in the commit description.
> Thanks for your comments, and sorry for replying late.
> I didn't get more details about this bit difference between i.MX8MP and
> others.
> Let me consult with design team again, and back to you later.

I got some details of this PERST bit(BIT3) of SRC_PCIEPHY_RCR.
The initialized default value of this bit is 1b'1 on i.MX7/iMX8MM/iMX8MQ.
But unfortunately, the i.MX8MP has one inverted default value 1b'0 of this bit.

And this bit should be kept 1b'1 after power and clocks are stable.
So, I assert/de-assert this bit on i.MX8MP only.

Best Regards
Richard Zhu

> 
> Best Regards
> Richard Zhu
> 
> >
> > regards
> > Philipp