Re: [PATCH v9 2/2] PCI: rockchip: Add Rockchip RK356X host controller driver

["Pali Rohár" <pali@kernel.org>]

On Thursday 24 June 2021 10:08:54 xxm wrote:
> 在 2021/6/23 22:33, Lorenzo Pieralisi 写道:
> > On Thu, May 06, 2021 at 10:35:44AM +0800, Simon Xue wrote:
> > > +static int rockchip_pcie_start_link(struct dw_pcie *pci)
> > > +{
> > > +	struct rockchip_pcie *rockchip = to_rockchip_pcie(pci);
> > > +
> > > +	/* Reset device */
> > > +	gpiod_set_value_cansleep(rockchip->rst_gpio, 0);
> > > +
> > > +	rockchip_pcie_enable_ltssm(rockchip);
> > > +
> > > +	/*
> > > +	 * PCIe requires the refclk to be stable for 100µs prior to releasing
> > > +	 * PERST. See table 2-4 in section 2.6.2 AC Specifications of the PCI
> > > +	 * Express Card Electromechanical Specification, 1.1. However, we don't
> > > +	 * know if the refclk is coming from RC's PHY or external OSC. If it's
> > > +	 * from RC, so enabling LTSSM is the just right place to release #PERST.
> > > +	 * We need more extra time as before, rather than setting just
> > > +	 * 100us as we don't know how long should the device need to reset.
> > > +	 */
> > > +	msleep(100);
> > Any rationale behind the time chosen ?
> We found some device need about 30ms, so 100ms here just leave more room for
> other devices.

Can you share information which PCIe card needs 30ms?

Last year I did tests with more WiFi AC cards and "the slowest" one was
Compex WLE1216 which needed about 11ms (more than 10ms). All other cards
were happy with just 1-2ms.