On Monday 22 November 2021 10:41:56 Marc Zyngier wrote:
> While the Apple PCIe driver works correctly when directly booted
> from the firmware, it fails to initialise when the kernel is booted
> from a bootloader using PCIe such as u-boot.
>
> That's beacuse we're missing a proper reset of the port (we only
> clear the reset, but never assert it).
>
> The PCIe spec requirements are two-fold:
>
> - #PERST must be asserted before setting up the clocks, and
> stay asserted for at least 100us (Tperst-clk).
>
> - Once #PERST is deasserted, the OS must wait for at least 100ms
> "from the end of a Conventional Reset" before we can start talking
> to the devices
>
> Implementing this results in a booting system.
>
> Fixes: 1e33888fbe44 ("PCI: apple: Add initial hardware bring-up")
> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> Cc: Alyssa Rosenzweig <alyssa@xxxxxxxxxxxxx>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Cc: Pali Rohár <pali@xxxxxxxxxx>
Looks good, but see comment below.
Acked-by: Pali Rohár <pali@xxxxxxxxxx>
> ---
> drivers/pci/controller/pcie-apple.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/pci/controller/pcie-apple.c b/drivers/pci/controller/pcie-apple.c
> index 1bf4d75b61be..957960a733c4 100644
> --- a/drivers/pci/controller/pcie-apple.c
> +++ b/drivers/pci/controller/pcie-apple.c
> @@ -539,13 +539,23 @@ static int apple_pcie_setup_port(struct apple_pcie *pcie,
>
> rmw_set(PORT_APPCLK_EN, port->base + PORT_APPCLK);
>
> + /* Engage #PERST before setting up the clock */
> + gpiod_set_value(reset, 0);
> +
> ret = apple_pcie_setup_refclk(pcie, port);
> if (ret < 0)
> return ret;
>
> + /* The minimal Tperst-clk value is 100us (PCIe CMS r2.0, 2.6.2) */
> + usleep_range(100, 200);
> +
> + /* Deassert #PERST */
> rmw_set(PORT_PERST_OFF, port->base + PORT_PERST);
> gpiod_set_value(reset, 1);
+ Luca
Just one comment. PERST# (PCIe Reset) is active-low signal. De-asserting
means to really set value to 1.
But there was a discussion that de-asserting should be done by call:
gpiod_set_value(reset, 0);
https://lore.kernel.org/linux-pci/51be082a-ff10-8a19-5648-f279aabcac51@xxxxxxxxxxxxxxxx/
Could we make this new pcie-apple.c driver to use gpiod_set_value(reset, 0)
for de-asserting, like in other drivers?
>
> + /* Wait for 100ms after #PERST deassertion (PCIe r2.0, 6.6.1) */
> + msleep(100);
> +
> ret = readl_relaxed_poll_timeout(port->base + PORT_STATUS, stat,
> stat & PORT_STATUS_READY, 100, 250000);
> if (ret < 0) {
> --
> 2.30.2
>
