Hello Sasha,
On Sun, Aug 03, 2025 at 08:27:07PM -0400, Sasha Levin wrote:
From: Nylon Chen nylon.chen@sifive.com
[ Upstream commit 7dbc4432ea6bf9d709391eb57f1e9fb44e99845a ]
The `frac` variable represents the pulse inactive time, and the result of this algorithm is the pulse active time. Therefore, we must reverse the result.
Although the SiFive Reference Manual states "pwms >= pwmcmpX -> HIGH", the hardware behavior is inverted due to a fixed XNOR with 0. As a result, the pwmcmp register actually defines the low (inactive) portion of the pulse.
The reference is SiFive FU740-C000 Manual[0]
Link: https://sifive.cdn.prismic.io/sifive/1a82e600-1f93-4f41-b2d8-86ed8b16acba_fu... [0]
Co-developed-by: Zong Li zong.li@sifive.com Signed-off-by: Zong Li zong.li@sifive.com Co-developed-by: Vincent Chen vincent.chen@sifive.com Signed-off-by: Vincent Chen vincent.chen@sifive.com Signed-off-by: Nylon Chen nylon.chen@sifive.com Link: https://lore.kernel.org/r/20250529035341.51736-3-nylon.chen@sifive.com Signed-off-by: Uwe Kleine-König ukleinek@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org
As for the 6.1[1] backport, please don't pick this change.
Best regards Uwe
[1] https://lore.kernel.org/all/52ycm5nf2jrxdmdmcijz57xhm2twspjmmiign6zq6rp3d5wt...