Infineon S25FL064L QSPI Flash: accessing the "secure regions"

[sjlongland]

Hi all,

Silly question regarding the QSPI NOR flash driver. I have a custom board that uses a Infineon S25FL064L (SOIC-8 form factor) hooked up to a Nordic Semiconductor nRF52840 MCU. This chip has four 256kB "security regions" that can be programmed and kept separate from the main flash array.

Other chips like the ISSI IS25LP016D have the same feature (called "security rows" there).

In a previous project, I used one of these security regions to store a true-random generated blob of data that I then used to generate static tokens that had to be unique to each device. One example was the Thread joiner credential, which we then put on a label that gets fixed to the case of the device in question: this is something that I don't want to lose in a factory reset and the security rows are protected from such accidental erasure.

Question is, how do I access it in Zephyr? I have a nordic,qspi-nor device configured like so (minor nit, only fastread seems to work properly as a read mode, read4o sort-of works, but is intermittent, haven't figured out why):

&qspi {
	status = "okay";
	pinctrl-0 = <&qspi_default>;
	pinctrl-1 = <&qspi_sleep>;
	pinctrl-names = "default", "sleep";
	s25fl064l: s25fl064l@0 {
		status = "okay";
		compatible = "nordic,qspi-nor";
		reg = <0>;
		label = "S25FL064L";
		/* Source: https://devzone.nordicsemi.com/f/nordic-q-a/103697/nrf5340---qspi-has-slower-performance-than-single-lane-spi-with-external-qspi-flash#fragment-684_votecb90d471-ab1b-49bc-914e-21d2d29f1612 */
		/*
		 * S25FL064L supports pp4o (Quad Page Program (QPP) instruction 0x32) and pp
		 */
		writeoc = "pp4o";
		/* S25FL064L supports all read operations, only fastread seems to work right now */
		readoc = "fastread";
		quad-enable-requirements = "S2B1v5";
		sck-frequency = <108000000>;
		jedec-id = [01 60 17];
		sfdp-bfp = [
			e5 20 fb ff  ff ff ff 03  48 eb 08 6b  08 3b 88 bb
			fe ff ff ff  ff ff ff ff  ff ff 48 eb  0c 20 0f 52
			10 d8 00 ff  31 92 0d ff  81 66 4e cd  cc 83 18 44
			7a 75 7a 75  f7 a2 d5 5c  22 f6 5d ff  e8 50 f8 a1
		];
		size = <67108864>;
		/* has-dpd; */
		/* t-enter-dpd = <3000>; */
		/* t-exit-dpd = <5000>; */

		partitions {
			compatible = "fixed-partitions";
			#address-cells = <1>;
			#size-cells = <1>;

			/* … etc … */
		};
	};
};

The datasheet tells me the opcodes for secure row access:

• SECRR (0x48): Security Region Read
• SECRP (0x42): Security Region Program
• SECRE (0x40): Security Region Erase

Where would I go to try sending such commands to the QSPI flash?