Re: [PATCH v3 1/2] PCI: rockchip-host: Fix rockchip_pcie_host_init_port() PERST# handling

[Bjorn Helgaas <helgaas@kernel.org>]

On Fri, Apr 12, 2024 at 11:37:20AM +0900, Damien Le Moal wrote:
> The PCIe specifications (PCI Express Electromechanical Specification rev
> 2.0, section 2.6.2) mandate that the PERST# signal must remain asserted

"PCIe CEM r5.1, sec 2.9.2"

> for at least 100 usec (Tperst-clk) after the PCIe reference clock
> becomes stable (if a reference clock is supplied), and for at least
> 100 msec after the power is stable (Tpvperl, defined by the macro
> PCIE_T_PVPERL_MS).
> 
> Modify rockchip_pcie_host_init_port() to satisfy these constraints by
> adding a sleep period before bringing back PESRT# signal to high using

s/PESRT#/PERST#/
s/bringing back PERST# to high/deasserting PERST#/

Whoever applies this can probably fix these up for you.

> the ep_gpio GPIO. Since Tperst-clk is the shorter wait time, add an
> msleep() call for the longer PCIE_T_PVPERL_MS milliseconds to handle
> both timing requirements.
> 
> Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
> ---
>  drivers/pci/controller/pcie-rockchip-host.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/pci/controller/pcie-rockchip-host.c b/drivers/pci/controller/pcie-rockchip-host.c
> index 300b9dc85ecc..fc868251e570 100644
> --- a/drivers/pci/controller/pcie-rockchip-host.c
> +++ b/drivers/pci/controller/pcie-rockchip-host.c
> @@ -322,6 +322,7 @@ static int rockchip_pcie_host_init_port(struct rockchip_pcie *rockchip)
>  	rockchip_pcie_write(rockchip, PCIE_CLIENT_LINK_TRAIN_ENABLE,
>  			    PCIE_CLIENT_CONFIG);
>  
> +	msleep(PCIE_T_PVPERL_MS);

Looks good, thanks!

>  	gpiod_set_value_cansleep(rockchip->ep_gpio, 1);
>  
>  	/* 500ms timeout value should be enough for Gen1/2 training */
> -- 
> 2.44.0
>