linux-kernel - Re: [PATCH v1 0/1] phy: freescale: imx8m-pcie: facing pcie link-up instability

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Date: Fri, 22 Mar 2024 13:29:05 -0300
From: Fabio Estevam <festevam@...il.com>
To: Marcel Ziswiler <marcel@...wiler.com>
Cc: linux-phy@...ts.infradead.org, linux-imx@....com, 
	Lucas Stach <l.stach@...gutronix.de>, linux-arm-kernel@...ts.infradead.org, 
	kernel@...gutronix.de, Richard Zhu <hongxing.zhu@....com>, linux-kernel@...r.kernel.org, 
	Marcel Ziswiler <marcel.ziswiler@...adex.com>, Heiko Stuebner <heiko@...ech.de>, 
	Kishon Vijay Abraham I <kishon@...nel.org>, Marc Kleine-Budde <mkl@...gutronix.de>, Rob Herring <robh@...nel.org>, 
	Sascha Hauer <s.hauer@...gutronix.de>, Shawn Guo <shawnguo@...nel.org>, 
	Tim Harvey <tharvey@...eworks.com>, Vinod Koul <vkoul@...nel.org>, 
	Yang Li <yang.lee@...ux.alibaba.com>, imx@...ts.linux.dev
Subject: Re: [PATCH v1 0/1] phy: freescale: imx8m-pcie: facing pcie link-up instability

Hi Marcel,

On Fri, Mar 22, 2024 at 10:07 AM Marcel Ziswiler <marcel@...wiler.com> wrote:
>
> From: Marcel Ziswiler <marcel.ziswiler@...adex.com>
>
>
> 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.MX8M 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). Maybe somebody
> from NXP could further comment on this?
>
> 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.
>
> [1] https://www.delock.com/produkt/95233/merkmale.html
> [2] https://github.com/nxp-imx/linux-imx/blob/lf-5.15.71-2.2.0/drivers/pci/controller/dwc/pci-imx6.c#L1548

The detailed information above is important. It should be in the
commit log of the patch IMHO.

Thanks for the fix.