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

Manivannan Sadhasivam
2024-04-15T06:48:25Z

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
> 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
> 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>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

- Mani

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

--
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