[ Upstream commit c0b9375454 ]
RK3588 TRM, section "11.6.1.3.3 Hot Reset and Link-Down Reset" states that:
If you want to delay link re-establishment (after reset) so that you can
reprogram some registers through DBI, you must set app_ltssm_enable =0
immediately after core_rst_n as shown in above. This can be achieved by
enable the app_dly2_en, and end-up the delay by assert app_dly2_done.
I.e. setting app_dly2_en will automatically deassert app_ltssm_enable on
a hot reset, and setting app_dly2_done will re-assert app_ltssm_enable,
re-enabling link training.
When receiving a hot reset/link-down IRQ when running in EP mode, we will
call dw_pcie_ep_linkdown(), which may update registers through DBI. Unless
link training is inhibited, these register updates race with the link
training.
To avoid the race, set PCIE_LTSSM_APP_DLY2_EN so the controller never
automatically trains the link after a link-down or hot reset interrupt.
That way any DBI updates done in the dw_pcie_ep_linkdown() path will happen
while the link is still down. Then allow link training by setting
PCIE_LTSSM_APP_DLY2_DONE
Co-developed-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Wilfred Mallawa <wilfred.mallawa@wdc.com>
Signed-off-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
[bhelgaas: commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20250613101908.2182053-2-cassel@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
ebe5861050