linux-kernel - Re: [RFC-PATCH] mtd: spi-nor: add conditional 4B opcodes

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Date:   Sun, 10 May 2020 10:43:36 +0000
From:   <Tudor.Ambarus@...rochip.com>
To:     <danielwa@...co.com>
CC:     <xe-linux-external@...co.com>, <miquel.raynal@...tlin.com>,
        <richard@....at>, <vigneshr@...com>,
        <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [RFC-PATCH] mtd: spi-nor: add conditional 4B opcodes

Hi, Daniel,

On Thursday, May 7, 2020 7:20:47 PM EEST Daniel Walker wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the
> content is safe
> 
> Some chips have 4B opcodes, but there is no way to know if they have
> them. This device tree option allows platform owners to force enable 4b
> opcodes when they know their chips support it even when it can be
> automatically identified.

I would like to detect this at run-time if possible. Maybe we can distinguish 
between the flavors of your flash by inspecting BFPT[16], bit 29. I'm planning 
to parse the 16th dword of BFPT. What does your flash return after applying 
the following patch?

diff --git a/drivers/mtd/spi-nor/sfdp.c b/drivers/mtd/spi-nor/sfdp.c
index f6038d3a3684..99f0ce57c7d0 100644
--- a/drivers/mtd/spi-nor/sfdp.c
+++ b/drivers/mtd/spi-nor/sfdp.c
@@ -457,6 +457,10 @@ static int spi_nor_parse_bfpt(struct spi_nor *nor,
        /* Fix endianness of the BFPT DWORDs. */
        le32_to_cpu_array(bfpt.dwords, BFPT_DWORD_MAX);
 
+       for(i = 0; i < BFPT_DWORD_MAX; i++)
+               dev_err(nor->dev, "bfpt.dwords[%d] = %08x\n",
+                       i + 1, bfpt.dwords[i]);
+
        /* Number of address bytes. */
        switch (bfpt.dwords[BFPT_DWORD(1)] & BFPT_DWORD1_ADDRESS_BYTES_MASK) {
        case BFPT_DWORD1_ADDRESS_BYTES_3_ONLY:
@@ -972,6 +976,9 @@ static int spi_nor_parse_4bait(struct spi_nor *nor,
        /* Fix endianness of the 4BAIT DWORDs. */
        le32_to_cpu_array(dwords, SFDP_4BAIT_DWORD_MAX);
 
+       for(i = 0; i < SFDP_4BAIT_DWORD_MAX; i++)
+               dev_err(nor->dev, "4bait[%d] = %08x\n", i, dwords[i]);
+
        /*
         * Compute the subset of (Fast) Read commands for which the 4-byte
         * version is supported.