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[84.226.167.205]) by smtp.googlemail.com with ESMTPSA id u5sm1657992wmg.9.2021.01.26.23.59.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 Jan 2021 23:59:03 -0800 (PST) Date: Wed, 27 Jan 2021 08:59:02 +0100 From: Krzysztof Kozlowski To: Arnd Bergmann Cc: Marek Szyprowski , "moderated list:ARM/SAMSUNG EXYNOS ARM ARCHITECTURES" , "linux-kernel@vger.kernel.org" , Sylwester Nawrocki , Vinod Koul , Kishon Vijay Abraham I , Bartlomiej Zolnierkiewicz , Willy Wolff , Marian Mihailescu Subject: Re: [PATCH 2/2] ARM: dts: exynos: use Exynos5420 dedicated USB2 PHY compatible Message-ID: <20210127075902.esm3tukq4pwmdf3j@kozik-lap> References: <20201120085637.7299-1-m.szyprowski@samsung.com> <20201120085637.7299-3-m.szyprowski@samsung.com> <20201120110503.GB26836@kozik-lap> <14102bab-33a1-45e0-0faf-883c7b1133a5@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 26, 2021 at 11:44:26PM +0100, Arnd Bergmann wrote: > On Fri, Nov 20, 2020 at 12:10 PM Marek Szyprowski > wrote: > > On 20.11.2020 12:05, Krzysztof Kozlowski wrote: > > > On Fri, Nov 20, 2020 at 09:56:37AM +0100, Marek Szyprowski wrote: > > >> USB2.0 PHY in Exynos5420 differs from Exynos5250 variant a bit, so use the > > >> recently introduced dedicated compatible for Exynos5420. > > >> > > >> Signed-off-by: Marek Szyprowski > > >> --- > > >> arch/arm/boot/dts/exynos54xx.dtsi | 6 +++--- > > >> 1 file changed, 3 insertions(+), 3 deletions(-) > > >> > > >> diff --git a/arch/arm/boot/dts/exynos54xx.dtsi b/arch/arm/boot/dts/exynos54xx.dtsi > > >> index fe9d34c23374..2ddb7a5f12b3 100644 > > >> --- a/arch/arm/boot/dts/exynos54xx.dtsi > > >> +++ b/arch/arm/boot/dts/exynos54xx.dtsi > > >> @@ -188,7 +188,7 @@ > > >> compatible = "samsung,exynos4210-ehci"; > > >> reg = <0x12110000 0x100>; > > >> interrupts = ; > > >> - phys = <&usb2_phy 1>; > > >> + phys = <&usb2_phy 0>; > > >> phy-names = "host"; > > >> }; > > >> > > >> @@ -196,12 +196,12 @@ > > >> compatible = "samsung,exynos4210-ohci"; > > >> reg = <0x12120000 0x100>; > > >> interrupts = ; > > >> - phys = <&usb2_phy 1>; > > >> + phys = <&usb2_phy 0>; > > >> phy-names = "host"; > > >> }; > > >> > > >> usb2_phy: phy@12130000 { > > >> - compatible = "samsung,exynos5250-usb2-phy"; > > >> + compatible = "samsung,exynos5420-usb2-phy"; > > > The DTS change will wait till PHY driver adjustements get merged... or > > > if the difference is not critical, maybe using both compatibles (5420 > > > and 5250) would have sense? > > > > It won't work easily with both compatibles, because in the 5420 variant > > I've also changed the PHY indices (5420 has no device and second hsic > > phy). IMHO the dts change can wait for the next release. > > I see this made it into the pull request now, but I had not been aware > of the change earlier, and I'm slightly annoyed to have received it this > way: > > - This is clearly an incompatible change to the dtb, and you all > noticed that because it would cause a bisection problem. As > a general rule, if a dts change does not work across bisection, > we should not merge it at all, because it causes problems for > anyone with external dts or dtb files. Hi Arnd, No, it does not create a bisection problem. The driver change adding new compatible is already in v5.11-rc1. > > - It would likely have been possible to define the new binding in > a backward-compatible way. I don't see a reason why the index > values in the binding had to change here, other than a slight > inconvenience for the driver. It does not matter since it's a new compatible and old one is not affected. Nothing got broken before this patch, nothing got broken after applying it via samsung-soc. No backwards compatibility is affected. > > - If the change was really unavoidable, I would have expected > a long explanation about why it had to be done in both the > commit message and in the tag description for the pull > request. > > I've dropped the pull request for now, maybe this can still > be sorted out with another driver change that makes the > new compatible string backward-compatible. It's a different hardware. New hardware does not have to be compatible with old hardware. However old DTB is still doing fine (although with the original issue not fixed). Best regards, Krzysztof