[REGRESSION] spi: cadence-quadspi: STIG mode results in timeouts for Micron MT25QL01 flash

[Stefan Kerkmann <s.kerkmann@xxxxxxxxxxxxxx>]

Hello,

I have run into the same regression when probing a Micron MT25QL01 SPI-NOR flash
on a Intel CycloneV platform (socfpga) as Yoshitaka Ikeda[1]. The regression
manifests in read timeouts. Bisecting the issue tracked it down to commit
"d403fb6e76bf8 spi: cadence-quadspi: use STIG mode for small reads". Reverting
the commit resolves the issue on v6.12-rc3. There are no custom patches applied,
except for the debugging output mentioned in the linked thread.

The good case is as follows:

```
[    1.063171] **********spi_mem_op dump**************
[    1.063183] addr: nbytes:0x0 , buswidth 0x0, dtr 0x0, val 0x0
[    1.068093] cmd: nbytes:0x1 , buswidth 0x1, dtr 0x0, opcode 0x9F
[    1.073837] data: nbytes:0x6 , buswidth 0x1, dtr 0x0, data dir 0x1
[    1.079823] ***************************************
[    1.086068] **********spi_mem_op dump**************
[    1.090931] addr: nbytes:0x3 , buswidth 0x1, dtr 0x0, val 0x0
[    1.095815] cmd: nbytes:0x1 , buswidth 0x1, dtr 0x0, opcode 0x5A
[    1.101543] data: nbytes:0x10 , buswidth 0x1, dtr 0x0, data dir 0x1
[    1.107547] ***************************************
[    1.113835] **********spi_mem_op dump**************
[    1.118695] addr: nbytes:0x3 , buswidth 0x1, dtr 0x0, val 0x10
[    1.123573] cmd: nbytes:0x1 , buswidth 0x1, dtr 0x0, opcode 0x5A
[    1.129395] data: nbytes:0x8 , buswidth 0x1, dtr 0x0, data dir 0x1
[    1.135392] ***************************************
[    1.141592] **********spi_mem_op dump**************
[    1.146471] addr: nbytes:0x3 , buswidth 0x1, dtr 0x0, val 0x0
[    1.151335] cmd: nbytes:0x1 , buswidth 0x1, dtr 0x0, opcode 0x5A
[    1.157072] data: nbytes:0x88 , buswidth 0x1, dtr 0x0, data dir 0x1
[    1.163058] ***************************************
[    1.169341] **********spi_mem_op dump**************
[    1.174219] addr: nbytes:0x3 , buswidth 0x1, dtr 0x0, val 0x30
[    1.179082] cmd: nbytes:0x1 , buswidth 0x1, dtr 0x0, opcode 0x5A
[    1.184904] data: nbytes:0x40 , buswidth 0x1, dtr 0x0, data dir 0x1
[    1.190890] ***************************************
[    1.197183] **********spi_mem_op dump**************
[    1.202045] addr: nbytes:0x3 , buswidth 0x1, dtr 0x0, val 0x80
[    1.206925] cmd: nbytes:0x1 , buswidth 0x1, dtr 0x0, opcode 0x5A
[    1.212740] data: nbytes:0x8 , buswidth 0x1, dtr 0x0, data dir 0x1
[    1.218736] ***************************************
[    1.224916] **********spi_mem_op dump**************
[    1.229776] addr: nbytes:0x0 , buswidth 0x0, dtr 0x0, val 0x0
[    1.234649] cmd: nbytes:0x1 , buswidth 0x1, dtr 0x0, opcode 0x6
[    1.240376] data: nbytes:0x0 , buswidth 0x0, dtr 0x0, data dir 0x0
[    1.246283] ***************************************
[    1.252443] **********spi_mem_op dump**************
[    1.257314] addr: nbytes:0x0 , buswidth 0x0, dtr 0x0, val 0x0
[    1.262176] cmd: nbytes:0x1 , buswidth 0x1, dtr 0x0, opcode 0xB7
[    1.267917] data: nbytes:0x0 , buswidth 0x0, dtr 0x0, data dir 0x0
[    1.273914] ***************************************
[    1.280074] **********spi_mem_op dump**************
[    1.284946] addr: nbytes:0x0 , buswidth 0x0, dtr 0x0, val 0x0
[    1.289809] cmd: nbytes:0x1 , buswidth 0x1, dtr 0x0, opcode 0x4
[    1.295544] data: nbytes:0x0 , buswidth 0x0, dtr 0x0, data dir 0x0
[    1.301444] ***************************************
[    1.307694] 5 fixed-partitions partitions found on MTD device ff705000.spi.0
[    1.319593] Creating 5 MTD partitions on "ff705000.spi.0":
[    1.325080] 0x000000000000-0x000000040000 : "preloader"
[    1.331825] 0x000000040000-0x0000000c0000 : "bootloader"
[    1.338645] 0x0000000c0000-0x0000000e0000 : "barebox-environment"
[    1.346299] 0x0000000e0000-0x000000110000 : "state-storage"
[    1.353319] 0x000000110000-0x000008000000 : "ubi"
```

With the STIG short read optimization enabled, the read timeouts occur:

```
[    0.931469] **********spi_mem_op dump**************
[    0.931482] addr: nbytes:0x0 , buswidth 0x0, dtr 0x0, val 0x0
[    0.936398] cmd: nbytes:0x1 , buswidth 0x1, dtr 0x0, opcode 0x9F
[    0.942129] data: nbytes:0x6 , buswidth 0x1, dtr 0x0, data dir 0x1
[    0.948132] ***************************************
[    0.954369] **********spi_mem_op dump**************
[    0.959233] addr: nbytes:0x3 , buswidth 0x1, dtr 0x0, val 0x0
[    0.964117] cmd: nbytes:0x1 , buswidth 0x1, dtr 0x0, opcode 0x5A
[    0.969845] data: nbytes:0x10 , buswidth 0x1, dtr 0x0, data dir 0x1
[    0.975844] ***************************************
[    1.482104] cadence-qspi ff705000.spi: Flash command execution timed out.
[    1.493754] **********spi_mem_op dump**************
[    1.493759] addr: nbytes:0x3 , buswidth 0x1, dtr 0x0, val 0x10
[    1.498623] cmd: nbytes:0x1 , buswidth 0x1, dtr 0x0, opcode 0x5A
[    1.504451] data: nbytes:0x8 , buswidth 0x1, dtr 0x0, data dir 0x1
[    1.510438] ***************************************
[    1.516611] spi-nor spi0.0: operation failed with -110
[    2.026639] cadence-qspi ff705000.spi: Flash command execution timed out.
[    2.033430] **********spi_mem_op dump**************
[    2.033437] addr: nbytes:0x0 , buswidth 0x0, dtr 0x0, val 0x0
[    2.038300] cmd: nbytes:0x1 , buswidth 0x1, dtr 0x0, opcode 0x6
[    2.044041] data: nbytes:0x0 , buswidth 0x0, dtr 0x0, data dir 0x0
[    2.049942] ***************************************
[    2.056112] spi-nor spi0.0: operation failed with -110
[    2.066110] spi-nor spi0.0: probe with driver spi-nor failed with error -110
```

The DT node for the flash is as follows:

```
&qspi {
	status = "okay";

	flash0: flash@0 {
		#address-cells = <1>;
		#size-cells = <1>;
		/* Micron MT25QL01 */
		compatible = "n25q00", "jedec,spi-nor";
		reg = <0>;	/* chip select */
		spi-max-frequency = <100000000>;
		m25p,fast-read;
		cdns,page-size = <256>;
		cdns,block-size = <16>;   /* 2^16, 64KB */
		cdns,read-delay = <4>;    /* delay value in read data capture register */
		cdns,tshsl-ns = <50>;
		cdns,tsd2d-ns = <50>;
		cdns,tchsh-ns = <4>;
		cdns,tslch-ns = <4>;
	};
};
```

Regards,
Stefan Kerkmann

[1]:
https://lore.kernel.org/lkml/OSZPR01MB70048CE259A3D63C4179199A8B659@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/#t

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