linux-kernel - Re: [PATCH 2/2] ARM: dts: at91: sama5d27_som1

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Date:   Mon, 12 Aug 2019 15:38:34 +0000
From:   <Eugen.Hristev@...rochip.com>
To:     <adrian.hunter@...el.com>, <Nicolas.Ferre@...rochip.com>,
        <alexandre.belloni@...tlin.com>, <ulf.hansson@...aro.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-mmc@...r.kernel.org>
Subject: Re: [PATCH 2/2] ARM: dts: at91: sama5d27_som1_ek: add mmc
 capabilities for SDMMC0



On 09.08.2019 09:23, Ludovic Desroches wrote:
> On Thu, Aug 08, 2019 at 03:57:30PM +0300, Adrian Hunter wrote:
>> On 8/08/19 3:42 PM, Ludovic Desroches wrote:
>>> On Thu, Aug 08, 2019 at 10:35:43AM +0200, Eugen Hristev - M18282 wrote:
>>>> From: Eugen Hristev <eugen.hristev@...rochip.com>
>>>>
>>>> Add mmc capabilities for SDMMC0 for this board.
>>>> With this enabled, eMMC connected card is detected as:
>>>>
>>>> mmc0: new DDR MMC card at address 0001
>>>>
>>>> Signed-off-by: Eugen Hristev <eugen.hristev@...rochip.com>
>>> Acked-by: Ludovic Desroches <ludovic.desroches@...rochip.com>
>>>
>>> I am interested to have the some insights about the use of sd-uhs-*
>>> properties.
>>>
>>> Our IP can't deal with 1V8 by itself. It has a 1V8SEL signal which can
>>> be used as the logic control input of a mux. So even if the IP claims
>>> to support UHS modes, it depends on the board.
>>>
>>> Are the sd-uhs-* properties a way to deal with this? I tend to think no
>>> as sdhci_setup_host() will set the caps depending on the content of the
>>> capabilities register. Do we have to use the SDHCI_QUIRK_MISSING_CAPS
>>> quirk or sdhci-caps/sdhci-caps-mask?
>>
>> There is "no-1-8-v" which it looks like sdhci-of-at91.c already supports:
>>
>>    sdhci_at91_probe() -> sdhci_get_of_property() -> sdhci_get_property()
>>
>>      	if (device_property_present(dev, "no-1-8-v"))
>> 		host->quirks2 |= SDHCI_QUIRK2_NO_1_8_V;
>>
> 
> Right, I forgot this property. Thanks.
> 
> Eugen, do you see cases we can't cover with this property?

Hi,

For current requirements and driver support, this should be enough.

I noticed one thing regarding SD-Cards, if I add property sd-uhs-sdr104 
the class 10 uhs1 cards are detected as SDR104 . Without this property 
they are detected as DDR50. Any idea why the difference ? The controller 
does not claim to have SDR104 support ?  We should add it ?

Eugen

> 
> Regards
> 
> Ludovic
> 
>>
>>>
>>> Regards
>>>
>>> Ludovic
>>>
>>>> ---
>>>>   arch/arm/boot/dts/at91-sama5d27_som1_ek.dts | 1 +
>>>>   1 file changed, 1 insertion(+)
>>>>
>>>> diff --git a/arch/arm/boot/dts/at91-sama5d27_som1_ek.dts b/arch/arm/boot/dts/at91-sama5d27_som1_ek.dts
>>>> index 149e539..194b3a3 100644
>>>> --- a/arch/arm/boot/dts/at91-sama5d27_som1_ek.dts
>>>> +++ b/arch/arm/boot/dts/at91-sama5d27_som1_ek.dts
>>>> @@ -54,6 +54,7 @@
>>>>   
>>>>   		sdmmc0: sdio-host@...00000 {
>>>>   			bus-width = <8>;
>>>> +			mmc-ddr-3_3v;
>>>>   			pinctrl-names = "default";
>>>>   			pinctrl-0 = <&pinctrl_sdmmc0_default>;
>>>>   			status = "okay";
>>>> -- 
>>>> 2.7.4
>>>>
>>>
>>
>