linux-kernel - Re: [PATCH v2] phy: freescale: imx8m-pcie: fix pcie link-up instability

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Message-ID: <7ba92b06aecb4d8894ba9ec8f92376bd971d2a72.camel@toradex.com>
Date: Sun, 7 Apr 2024 22:23:45 +0000
From: Marcel Ziswiler <marcel.ziswiler@...adex.com>
To: "linux-phy@...ts.infradead.org" <linux-phy@...ts.infradead.org>,
	"vkoul@...nel.org" <vkoul@...nel.org>
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Subject: Re: [PATCH v2] phy: freescale: imx8m-pcie: fix pcie link-up
 instability

Hi Vinod

On Sat, 2024-04-06 at 14:48 +0530, Vinod Koul wrote:
> 
> On Wed, 27 Mar 2024 08:19:37 +0100, Marcel Ziswiler wrote:
> > On the i.MX 8M Mini, the AUX_PLL_REFCLK_SEL has to be left at its reset
> > default of AUX_IN (PLL clock).
> > 
> > Background Information:
> > In our automated testing setup, we use Delock Mini-PCIe SATA cards [1].
> > While this setup has proven very stable overall we noticed upstream on
> > the i.MX 8M Mini fails quite regularly (about 50/50) to bring up the
> > PCIe link while with NXP's downstream BSP 5.15.71_2.2.2 it always works.
> > As that old downstream stuff was quite different, I first also tried
> > NXP's latest downstream BSP 6.1.55_2.2.0 which from a PCIe point of view
> > is fairly vanilla, however, also there the PCIe link-up was not stable.
> > Comparing and debugging I noticed that upstream explicitly configures
> > the AUX_PLL_REFCLK_SEL to I_PLL_REFCLK_FROM_SYSPLL while working
> > downstream [2] leaving it at reset defaults of AUX_IN (PLL clock).
> > Unfortunately, the TRM does not mention any further details about this
> > register (both for the i.MX 8M Mini as well as the Plus).
> > NXP confirmed their validation codes for the i.MX8MM PCIe doesn't
> > configure cmn_reg063 (offset: 0x18C).
> > BTW: On the i.MX 8M Plus we have not seen any issues with PCIe with the
> > exact same setup which is why I left it unchanged.
> > 
> > [...]
> 
> Applied, thanks!
> 
> [1/1] phy: freescale: imx8m-pcie: fix pcie link-up instability
>       commit: 3a161017f1de55cc48be81f6156004c151f32677

Sorry, but it is slightly confusing whether v1 or v2 now got applied. I believe v1 but then only the commit
messages differ. However, please note that only v2 included information on how to proceed concerning
backporting to stable 6.1.x.

Thanks!

> Best regards,
> --
> -Vinod

Cheers

Marcel