linux-kernel - Re: [PATCH] Revert "mtd: spinand: esmt: fix id code for F50D1G41LB"

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Message-ID: <b33fc77b-81f6-1628-bdf3-20b1d51e774c@quicinc.com>
Date: Mon, 8 Dec 2025 15:56:20 +0530
From: Md Sadre Alam <quic_mdalam@...cinc.com>
To: George Moussalem <george.moussalem@...look.com>,
        Miquel Raynal
	<miquel.raynal@...tlin.com>,
        Ziyang Huang <hzyitc@...look.com>
CC: <richard@....at>, <vigneshr@...com>, <tudor.ambarus@...aro.org>,
        <mmkurbanov@...utedevices.com>, <linux-mtd@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Revert "mtd: spinand: esmt: fix id code for F50D1G41LB"

Hi,

On 12/8/2025 2:56 PM, George Moussalem wrote:
> 
> 
> On 12/8/25 12:33, Miquel Raynal wrote:
>> On 02/12/2025 at 23:05:56 +08, Ziyang Huang <hzyitc@...look.com> wrote:
>>
>>> This reverts commit dd26402642a0899fde59ea6b0852fad3d799b4cc.
>>>
>>> The issue George met is due to the limit of QPIC, not the issue of the
>>> flash chip.
>>>
>>> QPIC only supports 4 bytes ID. So the fifth byte is always 0.
>>>
>>> If we use spi-gpio, the fifth byte can be read correctly.
>>>
>>> Signed-off-by: Ziyang Huang <hzyitc@...look.com>
>>> ---
>>
>> So how do we solve that?
>>
>> Is there anything than can be done on the qpic side?
> 
> Hi Alam,
> 
> Is the hardware itself limited to reading 4 ID bytes only or is it a
> driver limitation?

The hardware itself is limited to returning 4 ID bytes. QPIC reads the 
device ID and places it into the QPIC_NAND_FLASH_READ_ID register, which 
is 32‑bit wide. As a result, only 4 bytes of the device ID are available 
to software. The register stores the ID bytes in the order [31:24] = 
byte 3, [23:16] = byte 2, [15:8] = byte 1, [7:0] = byte 0.

Thanks,
Alam.