Re: [PATCH 3/3] PCI: mediatek-gen3: Move reset/assert callbacks in .power_up()

["Jianjun Wang (王建军)" <Jianjun.Wang@mediatek.com>]

On Thu, 2024-11-07 at 17:08 +0100, Lorenzo Bianconi wrote:
> > On Thu, Nov 07, 2024 at 02:50:55PM +0100, Lorenzo Bianconi wrote:
> > > In order to make the code more readable, move phy and mac reset
> > > lines
> > > assert/de-assert configuration in .power_up callback
> > > (mtk_pcie_en7581_power_up/mtk_pcie_power_up).
> > > 
> > > Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> > > ---
> > >  drivers/pci/controller/pcie-mediatek-gen3.c | 24
> > > ++++++++++++++++--------
> > >  1 file changed, 16 insertions(+), 8 deletions(-)
> > > 
> > > diff --git a/drivers/pci/controller/pcie-mediatek-gen3.c
> > > b/drivers/pci/controller/pcie-mediatek-gen3.c
> > > index
> > > 8c8c733a145634cdbfefd339f4a692f25a6e24de..c0127d0fb4f059b9f9e8163
> > > 60130e183e8f0e990 100644
> > > --- a/drivers/pci/controller/pcie-mediatek-gen3.c
> > > +++ b/drivers/pci/controller/pcie-mediatek-gen3.c
> > > @@ -867,6 +867,13 @@ static int mtk_pcie_en7581_power_up(struct
> > > mtk_gen3_pcie *pcie)
> > >  	int err;
> > >  	u32 val;
> > >  
> > > +	/*
> > > +	 * The controller may have been left out of reset by the
> > > bootloader
> > > +	 * so make sure that we get a clean start by asserting resets
> > > here.
> > > +	 */
> > > +	reset_control_bulk_assert(pcie->soc->phy_resets.num_resets,
> > > +				  pcie->phy_resets);
> > > +	reset_control_assert(pcie->mac_reset);
> > 
> > Add blank line here.
> 
> ack, I will fix it.
> 
> > 
> > >  	/*
> > >  	 * Wait for the time needed to complete the bulk assert in
> > >  	 * mtk_pcie_setup for EN7581 SoC.
> > > @@ -941,6 +948,15 @@ static int mtk_pcie_power_up(struct
> > > mtk_gen3_pcie *pcie)
> > >  	struct device *dev = pcie->dev;
> > >  	int err;
> > >  
> > > +	/*
> > > +	 * The controller may have been left out of reset by the
> > > bootloader
> > > +	 * so make sure that we get a clean start by asserting resets
> > > here.
> > > +	 */
> > > +	reset_control_bulk_assert(pcie->soc->phy_resets.num_resets,
> > > +				  pcie->phy_resets);
> > > +	reset_control_assert(pcie->mac_reset);
> > > +	usleep_range(10, 20);
> > 
> > Unrelated to this patch, but since you're moving it, do you know
> > what
> > this delay is for?  Can we add a #define and a spec citation for
> > it?
> 
> I am not sure about it, this was already there.
> @Jianjun Wang: any input on it?

This delay is used to ensure the reset is effective. A delay of 10us
should be sufficient in this scenario.

> 
> > 
> > Is there a requirement that the PHY and MAC reset ordering be
> > different for EN7581 vs other chips?
> > 
> > EN7581:
> > 
> >   assert PHY reset
> >   assert MAC reset
> >   power on PHY
> >   deassert PHY reset
> >   deassert MAC reset
> > 
> > others:
> > 
> >   assert PHY reset
> >   assert MAC reset
> >   deassert PHY reset
> >   power on PHY
> >   deassert MAC reset
> > 
> > Is there one order that would work for both?
> 
> EN7581 requires to run phy_init()/phy_power_on() before deassert PHY
> reset
> lines.
> 
> Regards,
> Lorenzo
> 
> > 
> > >  	/* PHY power on and enable pipe clock */
> > >  	err = reset_control_bulk_deassert(pcie->soc-
> > > >phy_resets.num_resets, pcie->phy_resets);
> > >  	if (err) {
> > > @@ -1013,14 +1029,6 @@ static int mtk_pcie_setup(struct
> > > mtk_gen3_pcie *pcie)
> > >  	 * counter since the bulk is shared.
> > >  	 */
> > >  	reset_control_bulk_deassert(pcie->soc->phy_resets.num_resets,
> > > pcie->phy_resets);
> > > -	/*
> > > -	 * The controller may have been left out of reset by the
> > > bootloader
> > > -	 * so make sure that we get a clean start by asserting resets
> > > here.
> > > -	 */
> > > -	reset_control_bulk_assert(pcie->soc->phy_resets.num_resets,
> > > pcie->phy_resets);
> > > -
> > > -	reset_control_assert(pcie->mac_reset);
> > > -	usleep_range(10, 20);
> > >  
> > >  	/* Don't touch the hardware registers before power up */
> > >  	err = pcie->soc->power_up(pcie);
> > > 
> > > -- 
> > > 2.47.0
> > >