[PATCH v2 4/4] spi: cadence-quadspi: use STIG mode for small reads

[Yoshitaka Ikeda]

Hi Dhruva,

> > - Error at startup
> >    - Kernel log
> > [    0.980598] **********spi_mem_op dump**************
> > [    0.980613] addr: nbytes:0x0 , buswidth 0x0, dtr 0x0, val 0x0
> > [    0.984223] cmd: nbytes:0x1 , buswidth 0x1, dtr 0x0, opcode 0x9F
> > [    0.988656] data: nbytes:0x6 , buswidth 0x1, dtr 0x0, data dir 0x1
> > [    0.993362] ***************************************
> > [    0.998329] spi-nor spi0.0: found mt25ql512a, expected n25q512a
> > [    1.006574] **********spi_mem_op dump**************
> > [    1.006583] addr: nbytes:0x3 , buswidth 0x1, dtr 0x0, val 0x0
> > [    1.010150] cmd: nbytes:0x1 , buswidth 0x1, dtr 0x0, opcode 0x5A
> > [    1.014596] data: nbytes:0x10 , buswidth 0x1, dtr 0x0, data dir 0x1
> > [    1.019285] ***************************************
> > [    1.524271] cadence-qspi ff705000.flash: Flash command execution
> timed out.
> 
> This print message is from cqspi_exec_flash_cmd. This function should only
> be called from cqspi_command_read/write .
> 
> However, from spi_mem_op dump that you have provided above, where
> addr.nbytes is 3 and data.nbytes is 0x10 (which is > 8) it should never have
> entered the cqspi_command_read function.

The location of the log output is after the call to cqspi_mem_process(), so I assume it is called with the following data.

[ 1.533483] **********spi_mem_op dump**************
[ 1.533489] addr: nbytes:0x3 , buswidth 0x1, dtr 0x0, val 0x10
[ 1.537055] cmd: nbytes:0x1 , buswidth 0x1, dtr 0x0, opcode 0x5A
[ 1.541579] data: nbytes:0x8 , buswidth 0x1, dtr 0x0, data dir 0x1
[ 1.546266] ***************************************

Thus, the condition is met and cqspi_command_read() is called.
We have also applied the following patch and confirmed that it is called.

- patch
```
diff --git a/drivers/spi/spi-cadence-quadspi.c b/drivers/spi/spi-cadence-quadspi.c
index 64b6a460d739..8d3681e1f35c 100644
--- a/drivers/spi/spi-cadence-quadspi.c
+++ b/drivers/spi/spi-cadence-quadspi.c
@@ -1365,15 +1365,21 @@ static int cqspi_mem_process(struct spi_mem *mem, const struct spi_mem_op *op)
 	 * reads, prefer STIG mode for such small reads.
 	 */
 		if (!op->addr.nbytes ||
-		    op->data.nbytes <= CQSPI_STIG_DATA_LEN_MAX)
+		    op->data.nbytes <= CQSPI_STIG_DATA_LEN_MAX) {
+			printk("----- %d:%s() (1) -----\n", __LINE__, __func__);
 			return cqspi_command_read(f_pdata, op);
+		}
 
+		printk("----- %d:%s() (2) -----\n", __LINE__, __func__);
 		return cqspi_read(f_pdata, op);
 	}
 
-	if (!op->addr.nbytes || !op->data.buf.out)
+	if (!op->addr.nbytes || !op->data.buf.out) {
+		printk("----- %d:%s() (3) -----\n", __LINE__, __func__);
 		return cqspi_command_write(f_pdata, op);
+	}
 
+	printk("----- %d:%s() (4) -----\n", __LINE__, __func__);
 	return cqspi_write(f_pdata, op);
 }

```

- log
```
[    0.786600] ----- 1369:cqspi_mem_process() (1) -----
[    0.790312] **********spi_mem_op dump**************
[    0.790319] addr: nbytes:0x0 , buswidth 0x0, dtr 0x0, val 0x0
[    0.793885] cmd: nbytes:0x1 , buswidth 0x1, dtr 0x0, opcode 0x9F
[    0.798325] data: nbytes:0x6 , buswidth 0x1, dtr 0x0, data dir 0x1
[    0.803013] ***************************************
[    0.807892] spi-nor spi0.0: found mt25ql512a, expected n25q512a
[    0.816062] ----- 1373:cqspi_mem_process() (2) -----
[    0.819775] **********spi_mem_op dump**************
[    0.819782] addr: nbytes:0x3 , buswidth 0x1, dtr 0x0, val 0x0
[    0.823348] cmd: nbytes:0x1 , buswidth 0x1, dtr 0x0, opcode 0x5A
[    0.827792] data: nbytes:0x10 , buswidth 0x1, dtr 0x0, data dir 0x1
[    0.832480] ***************************************
[    0.837442] ----- 1369:cqspi_mem_process() (1) -----
[    1.344671] cadence-qspi ff705000.flash: Flash command execution timed out.
[    1.350328] **********spi_mem_op dump**************
[    1.350334] addr: nbytes:0x3 , buswidth 0x1, dtr 0x0, val 0x10
[    1.353901] cmd: nbytes:0x1 , buswidth 0x1, dtr 0x0, opcode 0x5A
[    1.358427] data: nbytes:0x8 , buswidth 0x1, dtr 0x0, data dir 0x1
[    1.363114] ***************************************
[    1.367981] spi-nor spi0.0: operation failed with -110
[    1.375376] spi-nor spi0.0: mt25ql512a (65536 Kbytes)
```

> Please can you share the exact output of uname -a where you observe this
> error?

My environment has shortened the output of uname -a, so it may not be useful.
Instead, I will give you information about the kernel I am using.
It is the following (v6.3):
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=457391b0380335d5e9a5babdec90ac53928b23b4

> Are you carrying any sort of local patches? Can you make sure that the
> CQSPI_STIG_DATA_LEN_MAX is 8 in your case too?

There is no local patch and CQSPI_STIG_DATA_LEN_MAX remains 8.

-- 
Thanks and Regards,
Yoshitaka Ikeda