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

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Date: Sat, 6 Apr 2024 12:48:09 +0530
From: Vinod Koul <vkoul@...nel.org>
To: Marcel Ziswiler <marcel@...wiler.com>
Cc: linux-phy@...ts.infradead.org, linux-imx@....com,
	linux-kernel@...r.kernel.org, kernel@...gutronix.de,
	Richard Zhu <hongxing.zhu@....com>,
	Lucas Stach <l.stach@...gutronix.de>,
	linux-arm-kernel@...ts.infradead.org, stable@...r.kernel.org,
	Marcel Ziswiler <marcel.ziswiler@...adex.com>,
	Fabio Estevam <festevam@...il.com>,
	Heiko Stuebner <heiko@...ech.de>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Sergio Paracuellos <sergio.paracuellos@...il.com>,
	Shawn Guo <shawnguo@...nel.org>, Tim Harvey <tharvey@...eworks.com>,
	Yang Li <yang.lee@...ux.alibaba.com>, imx@...ts.linux.dev
Subject: Re: [PATCH v2] phy: freescale: imx8m-pcie: fix pcie link-up
 instability

On 27-03-24, 08:19, Marcel Ziswiler wrote:
> From: Marcel Ziswiler <marcel.ziswiler@...adex.com>
> 
> 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.

This does not apply on phy/fixes, pls rebase

-- 
~Vinod