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

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

On Fri, 2024-11-08 at 18:23 +0100, lorenzo@kernel.org wrote:
> On Nov 08, Bjorn Helgaas wrote:
> > On Fri, Nov 08, 2024 at 06:04:13PM +0100, lorenzo@kernel.org wrote:
> > > > On Fri, Nov 08, 2024 at 09:39:41AM +0100, lorenzo@kernel.org
> > > > wrote:
> > > > > > 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).
> > > > > > > > > +	/*
> > > > > > > > > +	 * 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.
> > > > > 
> > > > > ack, so we can introduce a marco like:
> > > > > 
> > > > > #define PCIE_RESET_TIME_US	10
> > > > > ...
> > > > > 
> > > > > usleep_range(PCIE_RESET_TIME_US, 2 * PCIE_RESET_TIME_US);
> > > > 
> > > > Unless this corresponds to a value specified by the PCIe base
> > > > spec
> > > > or CEM spec, this macro should be internal to
> > > > pcie-mediatek-gen3.c.
> > > 
> > > My plan is to add it in pcie-mediatek-gen3.c. Do you think
> > > PCIE_RESET_TIME_US is too generic?
> > 
> > It's generic, but so are most of the other #defines in
> > pcie-mediatek-gen3.c, so I'd follow suit.
> > 
> > Connect it to language in the MediaTek spec if possible, i.e., if
> > the
> > spec names this parameter, try to use the same name.
> 
> unfortunately I do not have any mediatek spec documentation
> available.
> 
> @Jianjun Wang: is PCIE_RESET_TIME_US fine for you or according to the
> available
> documentation?

It's fine for me.

Thanks.

> 
> Regards,
> Lorenzo