From:   "Shradha Todi" <shradha.t@samsung.com>
To:     "'Krzysztof Kozlowski'" <krzysztof.kozlowski@linaro.org>,
        <lpieralisi@kernel.org>, <kw@linux.com>, <robh@kernel.org>,
        <bhelgaas@google.com>, <krzysztof.kozlowski+dt@linaro.org>,
        <alim.akhtar@samsung.com>, <jingoohan1@gmail.com>,
        <Sergey.Semin@baikalelectronics.ru>, <lukas.bulwahn@gmail.com>,
        <hongxing.zhu@nxp.com>, <tglx@linutronix.de>,
        <m.szyprowski@samsung.com>, <jh80.chung@samsung.co>,
        <pankaj.dubey@samsung.com>
Cc:     <linux-pci@vger.kernel.org>, <devicetree@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-samsung-soc@vger.kernel.org>, <linux-kernel@vger.kernel.org>
In-Reply-To: <31e377b7-88bf-8737-0397-44ecca8cff54@linaro.org>
Subject: RE: [PATCH 06/16] arm64: dts: exynos: Rename the term elbi to appl
Date:   Thu, 2 Mar 2023 18:37:43 +0530
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> -----Original Message-----
> From: Krzysztof Kozlowski =5Bmailto:krzysztof.kozlowski=40linaro.org=5D
> Sent: 16 February 2023 16:34
> To: Shradha Todi <shradha.t=40samsung.com>; lpieralisi=40kernel.org;
> kw=40linux.com; robh=40kernel.org; bhelgaas=40google.com;
> krzysztof.kozlowski+dt=40linaro.org; alim.akhtar=40samsung.com;
> jingoohan1=40gmail.com; Sergey.Semin=40baikalelectronics.ru;
> lukas.bulwahn=40gmail.com; hongxing.zhu=40nxp.com; tglx=40linutronix.de;
> m.szyprowski=40samsung.com; jh80.chung=40samsung.co;
> pankaj.dubey=40samsung.com
> Cc: linux-pci=40vger.kernel.org; devicetree=40vger.kernel.org; linux-arm-
> kernel=40lists.infradead.org; linux-samsung-soc=40vger.kernel.org; linux-
> kernel=40vger.kernel.org
> Subject: Re: =5BPATCH 06/16=5D arm64: dts: exynos: Rename the term elbi t=
o appl
>=20
> On 14/02/2023 13:13, Shradha Todi wrote:
> > DT uses the name elbi in reg-names for application logic registers
> > which is a wrong nomenclature. This patch fixes the same.
> >
> > This commit shouldn't be applied without changes
> > =22dt-bindings: PCI: Rename the term elbi to appl=22 and
> > =22PCI: samsung: Rename the term elbi to appl=22
>=20
> Dependencies and patch ordering goes after '---', because there is no poi=
nt
> to store it in git history.
>=20

Understood will take care in next set of patches.

> Anyway, that's an ABI break and Exynos5433 is quite stable, so without cl=
ear
> indication of fixed bug, we should not do this.
>=20

We have strong technical reason to do so.

As per DWC PCIe UM, ELBI delivers an inbound register RD/WR received by the=
 controller to external application registers when the controller
is expected to generate the PCIe completion of this register RD/WR.
In this driver register space which is currently marked as ELBI, is not use=
d for this purpose (Not sure why original author has named this set of regi=
sters as ELBI)
So to keep this technically correct, it should be marked as application spe=
cific wrapper register space.
We used name as =22appl=22 taking reference from intel-gw-pcie.yaml's simil=
ar register space named as =22app=22, whereas in nvidia,tegra194-pcie.yaml =
it's named =22appl=22.=20

So our argument is if a future Samsung manufactured SoC having DWC PCIe con=
troller comes with support of real ELBI interface, we need to use the name =
elbi.
We know such SoC exists but they are not yet upstreamed.

Ready to adopt the best possible suggested method to make this happen but I=
 really think the name ELBI is misleading.

>=20
> Best regards,
> Krzysztof