Thread (3 messages) 3 messages, 2 authors, 2024-11-04

Re: [PATCH] PCI: j721e: Deassert PERST# after a delay of PCIE_T_PVPERL_MS ms

From: Siddharth Vadapalli <s-vadapalli@ti.com>
Date: 2024-11-04 07:08:49
Also in: linux-omap, linux-pci, lkml

On Sat, Nov 02, 2024 at 11:19:14PM +0900, Krzysztof Wilczyński wrote:
Hello,
quoted
According to Section 2.2 of the PCI Express Card Electromechanical
Specification (Revision 5.1), in order to ensure that the power and the
reference clock are stable, PERST# has to be deasserted after a delay of
100 milliseconds (TPVPERL). Currently, it is being assumed that the power
is already stable, which is not necessarily true. Hence, change the delay
to PCIE_T_PVPERL_MS to guarantee that power and reference clock are stable.
[...]
quoted
This patch is based on commit
c2ee9f594da8 KVM: selftests: Fix build on on non-x86 architectures
of Mainline Linux.
Why KVM?  Do you have the link to this commit handy?
Since this is a fix, I had based the patch on the latest Mainline Linux
with the head corresponding to the aforementioned commit. Link:
https://github.com/torvalds/linux/commit/c2ee9f594da8
[...]
quoted
 		if (pcie->reset_gpio) {
-			fsleep(PCIE_T_PERST_CLK_US);
+			msleep(PCIE_T_PVPERL_MS);
fsleep() with the same macro and for the same reason is also used in the
j721e_pcie_probe() callback.  I think, we would want both changed.
Thank you for pointing this out. I will update it in the v2 patch.

Regards,
Siddharth.
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