linux-kernel - Re: [PATCH] ARM: dts: at91: sama7g5ek: Align the impedance of the QSPI0's HSIO and PCB lines

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Date:   Thu, 7 Apr 2022 08:24:18 +0000
From:   <Claudiu.Beznea@...rochip.com>
To:     <Tudor.Ambarus@...rochip.com>, <Nicolas.Ferre@...rochip.com>
CC:     <alexandre.belloni@...tlin.com>, <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <Mihai.Sain@...rochip.com>
Subject: Re: [PATCH] ARM: dts: at91: sama7g5ek: Align the impedance of the
 QSPI0's HSIO and PCB lines

On 07.04.2022 10:51, Tudor Ambarus - M18064 wrote:
> On 4/7/22 09:26, Claudiu Beznea - M18063 wrote:
>> Hi, Tudor,
>>
>> On 06.04.2022 16:05, Tudor Ambarus wrote:
>>> The impedance of the QSPI PCB lines on the sama7g5ek is 50 Ohms.
>>> Align the output impedance of the QSPI0 HSIOs by setting a medium drive
>>> strength which corresponds to an impedance of 56 Ohms when VDD is in the
>>> 3.0V - 3.6V range. The high drive strength setting corresponds to an
>>> output impedance of 42 Ohms on the QSPI0 HSIOs.
>>>
>>> Suggested-by: Mihai Sain <mihai.sain@...rochip.com>
>>> Signed-off-by: Tudor Ambarus <tudor.ambarus@...rochip.com>
>>
>> Is it necessary a fixes tag here?
>>
> 
> It's not a fix per se, it's just a fine tuning that's why I chose to don't add
> the fixes tag. The memory that we have populated on sama7g5ek works fine even
> with high drive strength, but it's better to adjust it and use medium instead,
> in case some other flashes with higher frequencies are tested. If you think a
> fixes tag is needed, give me a sign and I'll resubmit.

Its good for me as is. Just wanted to be sure it hasn't been forgotten.
Thank you!

Reviewed-by: Claudiu Beznea <claudiu.beznea@...rochip.com>

> 
>>
>>> ---
>>>  arch/arm/boot/dts/at91-sama7g5ek.dts | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/arch/arm/boot/dts/at91-sama7g5ek.dts b/arch/arm/boot/dts/at91-sama7g5ek.dts
>>> index 08685a10eda1..8f9643170ba3 100644
>>> --- a/arch/arm/boot/dts/at91-sama7g5ek.dts
>>> +++ b/arch/arm/boot/dts/at91-sama7g5ek.dts
>>> @@ -655,7 +655,7 @@ pinctrl_qspi: qspi {
>>>  			 <PIN_PB21__QSPI0_INT>;
>>>  		bias-disable;
>>>  		slew-rate = <0>;
>>> -		atmel,drive-strength = <ATMEL_PIO_DRVSTR_HI>;
>>> +		atmel,drive-strength = <ATMEL_PIO_DRVSTR_ME>;
>>>  	};
>>>  
>>>  	pinctrl_sdmmc0_default: sdmmc0_default {
>>
>