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From: Christoph Niedermaier <cniedermaier@dh-electronics.com>
To: Marek Vasut <marex@denx.de>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Cc: Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Shawn Guo <shawnguo@kernel.org>, Li Yang <leoyang.li@nxp.com>,
	Fabio Estevam <festevam@denx.de>,
	NXP Linux Team <linux-imx@nxp.com>,
	kernel <kernel@dh-electronics.com>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Ulf Hansson <ulf.hansson@linaro.org>
Subject: RE: [PATCH 2/2] ARM: dts: imx6ull-dhcor: Add Marantec maveo box
Date: Thu, 6 Apr 2023 08:37:20 +0000	[thread overview]
Message-ID: <531df359744f4bdb9fd34eafc864d2bc@dh-electronics.com> (raw)
In-Reply-To: <42737c19-698f-8cc8-45b2-8ff08a274f87@denx.de>

From: Marek Vasut [mailto:marex@denx.de]
Sent: Wednesday, April 5, 2023 8:47 PM
> On 4/5/23 20:24, Christoph Niedermaier wrote:
>> From: Marek Vasut [mailto:marex@denx.de]
>> Sent: Wednesday, April 5, 2023 6:25 PM
>>> On 4/5/23 18:02, Christoph Niedermaier wrote:
>>>
>>> [...]
>>>
>>>> +/ {
>>>> +     model = "DH electronics i.MX6ULL DHCOR on maveo box";
>>>> +     compatible = "dh,imx6ull-dhcor-maveo-box", "dh,imx6ull-dhcor-som",
>>>> +                  "fsl,imx6ull";
>>>> +
>>>> +     aliases {
>>>> +             /delete-property/ mmc0; /* Avoid double definitions */
>>>> +             /delete-property/ mmc1;
>>>> +             mmc2 = &usdhc2; /* eMMC should be mmc2 */
>>>
>>> Why not mmc0 ?
>>>
>>> Use root=PARTUUID= when booting to avoid any dependency on
>>> root=/dev/mmcblk2pN enumeration.
>>
>> This is due to software interchangeability with the DHCOM
>> i.MX6ULL, where the eMMC is always mmc2.
> 
> +CC Ulf , I vaguely recall some discussion about this enumeration and I
> am not sure one can really depend on that.

That why I think it good to have a defined number for mmcblk devices
on an embedded system. An excerpt from [1]:

Alternative solutions like PARTUUIDs do not cover the case where multiple
mmcblk devices contain the same image. This is a common issue on devices
that can boot both from eMMC (for regular boot) and SD cards (as a
temporary boot medium for development). When a firmware image is
installed to eMMC after a test boot via SD card, there will be no
reliable way to refer to a specific device using (PART)UUIDs oder
LABELs

[1] https://patchwork.kernel.org/project/linux-mmc/patch/20200825134441.17537-2-matthias.schiffer@ew.tq-group.com/

So far I have never had a problem with numbering mmcblk devices via aliases.

Regards
Christoph
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Niedermaier <cniedermaier@dh-electronics.com>
To: Marek Vasut <marex@denx.de>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>
Cc: Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Shawn Guo <shawnguo@kernel.org>, Li Yang <leoyang.li@nxp.com>,
	Fabio Estevam <festevam@denx.de>,
	NXP Linux Team <linux-imx@nxp.com>,
	kernel <kernel@dh-electronics.com>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Ulf Hansson <ulf.hansson@linaro.org>
Subject: RE: [PATCH 2/2] ARM: dts: imx6ull-dhcor: Add Marantec maveo box
Date: Thu, 6 Apr 2023 08:37:20 +0000	[thread overview]
Message-ID: <531df359744f4bdb9fd34eafc864d2bc@dh-electronics.com> (raw)
In-Reply-To: <42737c19-698f-8cc8-45b2-8ff08a274f87@denx.de>

From: Marek Vasut [mailto:marex@denx.de]
Sent: Wednesday, April 5, 2023 8:47 PM
> On 4/5/23 20:24, Christoph Niedermaier wrote:
>> From: Marek Vasut [mailto:marex@denx.de]
>> Sent: Wednesday, April 5, 2023 6:25 PM
>>> On 4/5/23 18:02, Christoph Niedermaier wrote:
>>>
>>> [...]
>>>
>>>> +/ {
>>>> +     model = "DH electronics i.MX6ULL DHCOR on maveo box";
>>>> +     compatible = "dh,imx6ull-dhcor-maveo-box", "dh,imx6ull-dhcor-som",
>>>> +                  "fsl,imx6ull";
>>>> +
>>>> +     aliases {
>>>> +             /delete-property/ mmc0; /* Avoid double definitions */
>>>> +             /delete-property/ mmc1;
>>>> +             mmc2 = &usdhc2; /* eMMC should be mmc2 */
>>>
>>> Why not mmc0 ?
>>>
>>> Use root=PARTUUID= when booting to avoid any dependency on
>>> root=/dev/mmcblk2pN enumeration.
>>
>> This is due to software interchangeability with the DHCOM
>> i.MX6ULL, where the eMMC is always mmc2.
> 
> +CC Ulf , I vaguely recall some discussion about this enumeration and I
> am not sure one can really depend on that.

That why I think it good to have a defined number for mmcblk devices
on an embedded system. An excerpt from [1]:

Alternative solutions like PARTUUIDs do not cover the case where multiple
mmcblk devices contain the same image. This is a common issue on devices
that can boot both from eMMC (for regular boot) and SD cards (as a
temporary boot medium for development). When a firmware image is
installed to eMMC after a test boot via SD card, there will be no
reliable way to refer to a specific device using (PART)UUIDs oder
LABELs

[1] https://patchwork.kernel.org/project/linux-mmc/patch/20200825134441.17537-2-matthias.schiffer@ew.tq-group.com/

So far I have never had a problem with numbering mmcblk devices via aliases.

Regards
Christoph

  reply	other threads:[~2023-04-06  8:38 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-04-05 16:02 [PATCH 1/2] dt-bindings: arm: fsl: Add Marantec maveo box as a DHCOR i.MX6ULL SoM based board Christoph Niedermaier
2023-04-05 16:02 ` Christoph Niedermaier
2023-04-05 16:02 ` [PATCH 2/2] ARM: dts: imx6ull-dhcor: Add Marantec maveo box Christoph Niedermaier
2023-04-05 16:02   ` Christoph Niedermaier
2023-04-05 16:25   ` Marek Vasut
2023-04-05 16:25     ` Marek Vasut
2023-04-05 18:24     ` Christoph Niedermaier
2023-04-05 18:24       ` Christoph Niedermaier
2023-04-05 18:46       ` Marek Vasut
2023-04-05 18:46         ` Marek Vasut
2023-04-06  8:37         ` Christoph Niedermaier [this message]
2023-04-06  8:37           ` Christoph Niedermaier
2023-04-06 14:10           ` Marek Vasut
2023-04-06 14:10             ` Marek Vasut
2023-04-06 15:44             ` Christoph Niedermaier
2023-04-06 15:44               ` Christoph Niedermaier
2023-04-06 16:04               ` Marek Vasut
2023-04-06 16:04                 ` Marek Vasut
2023-04-06 16:36       ` Krzysztof Kozlowski
2023-04-06 16:36         ` Krzysztof Kozlowski
2023-04-06 17:32         ` Marek Vasut
2023-04-06 17:32           ` Marek Vasut
2023-04-06 18:03           ` Krzysztof Kozlowski
2023-04-06 18:03             ` Krzysztof Kozlowski
2023-04-05 16:26 ` [PATCH 1/2] dt-bindings: arm: fsl: Add Marantec maveo box as a DHCOR i.MX6ULL SoM based board Marek Vasut
2023-04-05 16:26   ` Marek Vasut
2023-04-05 18:13   ` Christoph Niedermaier
2023-04-05 18:13     ` Christoph Niedermaier

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