linux-kernel - Re: [RFC PATCH v5 2/6] mtd: rawnand: meson: wait for command in polling mode

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Message-ID: <163e0684-caff-77d0-1eaf-9a58290c200d@amlogic.com>
Date:   Mon, 5 Jun 2023 21:30:17 +0800
From:   Liang Yang <liang.yang@...ogic.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Arseniy Krasnov <avkrasnov@...rdevices.ru>
Cc:     Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        oxffffaa@...il.com, kernel@...rdevices.ru,
        linux-mtd@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v5 2/6] mtd: rawnand: meson: wait for command in
 polling mode



On 2023/6/5 21:19, Liang Yang wrote:
> Hi Miquel and Arseniy,
> 
> 
> On 2023/6/5 17:05, Miquel Raynal wrote:
>> [ EXTERNAL EMAIL ]
>>
>> Hi Arseniy,
>>
>>>>> @@ -1412,6 +1419,8 @@ static int meson_nfc_probe(struct 
>>>>> platform_device *pdev)
>>>>>             return ret;
>>>>>     }
>>>>>
>>>>> +  nfc->use_polling = of_property_read_bool(dev->of_node, "polling");
>>>>
>>>> This is a problem. You cannot add a polling property like that.
>>>>
>>>> There is already a nand-rb property which is supposed to carry how are
>>>> wired the RB lines. I don't see any in-tree users of the compatibles, I
>>>> don't know how acceptable it is to consider using soft fallback when
>>>> this property is missing, otherwise take the values of the rb lines
>>>> provided in the DT and user hardware control, but I would definitely
>>>> prefer that.
>>>
>>> I see. So i need to implement processing of this property here? And 
>>> if it
>>> is missed -> use software waiting. I think interesting thing will be 
>>> that:
>>>
>>> 1) Even with support of this property here, I really don't know how 
>>> to pass
>>>     RB values to this controller - I just have define for RB command 
>>> and that's
>>>     it. I found that this property is an array of u32 - IIUC each 
>>> element is
>>>     RB pin per chip. May be i need to dive into the old vendor's 
>>> driver to find
>>>     how to use RB values (although this driver uses software waiting 
>>> so I'm not
>>>     sure that I'll find something in it).
>>
>> Liang, can you please give use the relevant information here? How do we
>> target RB0 and RB1? It seems like you use the CS as only information
>> like if the RB lines where hardwired internally to a CS. Can we invert
>> the lines with a specific configuration?
> 
> Controllor has only one external RB pinmux (NAND_RB0). all the RB pins
> of different CEs need to be bound into one wire and connect with
> NAND_RB0 if want to use controller polling rb. the current operating
> CE of NAND is decided to "chip_select", of course controller internally 
> has different nfc commands to regconize which Ce's RB signal is polling.
> 
> <&nand_pins> in dts/yaml should include the NAND_RB0 if hardware 
> connects, or use software polling here.
> 
> @Arseniy, sorry, i don't travel all the informations yet. but why don't 
> you use the new RB_INT command with irq that i provided in another 
> thread. the new RB_INT command doesn't depend on the physical RB wires, 
> it also send the READ status command(0x70) and wait for the irq wake up 
> completion.

Use "nand-rb" in dts to decide old RB_INT(physical RB wires is needed) 
or new RB_INT(no physical RB wires). the new RB_INT command decides the 
RB0 or RB1 by the previous command with ce args.

> 
>> Arseniy, if the answer to my above question is no, then you should
>> expect the nand-rb and reg arrays to be identical. If they are not,
>> then you can return -EINVAL.
>>
>> If the nand-rb property is missing, then fallback to software wait.
>>
>>> 2) I can't test RB mode - I don't have such device :(
>>>
>>> Also for example in arasan-nand-controller.c parsed 'nand-rb' values 
>>> are used
>>> in controller specific register for waiting (I guess Meson controller 
>>> has something
>>> like that, but I don't have doc). While in marvell_nand.c it looks 
>>> like that they parse
>>> 'nand-rb' property, but never use it.
>>
>> Yes, the logic around the second RB line (taking care of CS1/CS3) is
>> slightly broken or at least badly documented, and thus should not be
>> used.
>>
>>>> In any case you'll need a dt-binding update which must be acked by
>>>> dt-binding maintainers.
>>>
>>> You mean to add this property desc to 
>>> Documentation/devicetree/bindings/mtd/amlogic,meson-nand.yaml ?
>>
>> Yes. In a dedicated patch. Something along the lines:
>>
>>          nand-rb: true
>>
>> inside the nand chip object should be fine. And flag the change as a
>> fix because we should have used and parsed this property since the
>> beginning.
>>
>> Thanks,
>> Miquèl