linux-kernel - Re: [PATCH 1/2] dt-bindings: mmc: mtk-sd: add single burst switch

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Message-ID: <b09f618a-eaf9-4258-ae2d-67eff1cb249f@collabora.com>
Date: Tue, 11 Mar 2025 10:47:23 +0100
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: Axe Yang (杨磊) <Axe.Yang@...iatek.com>,
 Wenbin Mei (梅文彬) <Wenbin.Mei@...iatek.com>,
 "conor+dt@...nel.org" <conor+dt@...nel.org>,
 Chaotian Jing (井朝天)
 <Chaotian.Jing@...iatek.com>, "robh@...nel.org" <robh@...nel.org>,
 "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
 "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>,
 "krzk+dt@...nel.org" <krzk+dt@...nel.org>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
 "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
 Andy-ld Lu (卢东) <Andy-ld.Lu@...iatek.com>,
 "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
 Yong Mao (毛勇) <yong.mao@...iatek.com>,
 "linux-arm-kernel@...ts.infradead.org"
 <linux-arm-kernel@...ts.infradead.org>,
 Qingliang Li (黎晴亮) <Qingliang.Li@...iatek.com>
Subject: Re: [PATCH 1/2] dt-bindings: mmc: mtk-sd: add single burst switch

Il 07/03/25 07:59, Axe Yang (杨磊) ha scritto:
> On Thu, 2025-03-06 at 10:19 +0100, AngeloGioacchino Del Regno wrote:
>> External email : Please do not click links or open attachments until
>> you have verified the sender or the content.
>>
>>
>> Il 06/03/25 09:48, Axe Yang ha scritto:
>>> Add 'mediatek,disable-single-burst' setting. This property can be
>>> used to switch bus burst type, from single burst to INCR, which is
>>> determined by the bus type within the IP. Some versions of the IP
>>> are using AXI bus, thus this switch is necessary as 'single' is not
>>> the burst type supported by the bus.
>>>
>>> Signed-off-by: Axe Yang <axe.yang@...iatek.com>
>>
>> I am mostly sure that this is not something to put in devicetree, but
>> as
>> platform data for specific SoC(s), as much as I'm mostly sure that
>> all of
>> the instances of the MSDC IP in one SoC will be *all* using either
>> single
>> or INCR.
> 
> No, actually MSDC IPs in one SoC are using different versions.
> Usually MSDC1 (index from 1) is used as eMMC host, the left hosts are
> used as SD/SDIO hosts. They have similar designs, but there are still
> difference.
> 
>>
>> So, I think I know the answer but I'll still ask just to be extremely
>> sure:
>>
>> is there any MediaTek SoC that has different IP versions for
>> different MSDC
>> instances, and that hence require single burst on one instance and
>> INCR on
>> another instance?
> 
> Yes. Actually every SoC has different IP versions for eMMC and SD/SDIO
> host as I said.
> e.g. For MT8168, signel burst bit should be set to 1 for eMMC Host, but
> 0 for SD/SDIO Host.
> 
>>
>> And if there is - is there a pattern? Is it always SDIO requiring
>> INCR or
>> always eMMC/SD requiring it?
>>
>>
> 
> No, there is no pattern. Both eMMC and SD/SDIO hosts need to be
> configured base on IP version. There is no binding relationship between
> eMMC/SD/SDIO and the burst type. eMMC burst type might be INCR or
> single, same as SD/SDIO.
> 

Okay but if there are different IP versions, and AXI/AHB is determined
by the IP version, why aren't you parsing the MAIN_VER/ECO_VER registers of
the MSDC IP to check whether to use INCR or SINGLE?

Cheers,
Angelo

> 
> Regards,
> Axe
> 
> 
>>
>>> ---
>>>    Documentation/devicetree/bindings/mmc/mtk-sd.yaml | 8 ++++++++
>>>    1 file changed, 8 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/mmc/mtk-sd.yaml
>>> b/Documentation/devicetree/bindings/mmc/mtk-sd.yaml
>>> index 0debccbd6519..6076aff0a689 100644
>>> --- a/Documentation/devicetree/bindings/mmc/mtk-sd.yaml
>>> +++ b/Documentation/devicetree/bindings/mmc/mtk-sd.yaml
>>> @@ -100,6 +100,14 @@ properties:
>>>        minimum: 0
>>>        maximum: 0xffffffff
>>>
>>> +  mediatek,disable-single-burst:
>>> +    $ref: /schemas/types.yaml#/definitions/flag
>>> +    description:
>>> +      Burst type setting. For some versions of the IP that do not
>>> use
>>> +      AHB bus, the burst type need to be switched to INCR.
>>> +      If present, use INCR burst type.
>>> +      If not present, use single burst type.
>>> +
>>>      mediatek,hs200-cmd-int-delay:
>>>        $ref: /schemas/types.yaml#/definitions/uint32
>>>        description:
>>
>>
>>