[M] Change in flashrom[1.2.x]: ichspi: Unify timeouts across all SPI operations to 30s

[Felix Singer (Code Review)]

Felix Singer has submitted this change. ( https://review.coreboot.org/c/flashrom/+/68691 )

Change subject: ichspi: Unify timeouts across all SPI operations to 30s
......................................................................

ichspi: Unify timeouts across all SPI operations to 30s

Note: This patch was backported from the master branch and it was
modified so that it can be applied on the 1.2.x branch.

`ich_hwseq_wait_for_cycle_complete()` drops taking `timeout` as argument
in favor of a fixed timeout of `30 seconds` for any given SPI operation
as recommended by the SPI programming guide.

Document: Alder Lake-P Client Platform SPI Programming Guide
          Rev 1.30 (supporting document for multi-master accessing the
                    SPI Flash device.)

Refer to below section to understand the problem in more detail and SPI
operation timeout recommendation from Intel in multi-master
scenarios.

On Intel Chipsets that support multi-mastering access of the SPI flash
may run into a timeout failure when the operation initiated from a
single master just follows the SPI operational timeout recommendation
as per the vendor datasheet (example: winbond spiflash W25Q256JV-DTR
specification, table 9.7).

In the multi-master SPI accessing scenario using hardware sequencing
operation, it's impossible to know the actual status of the SPI bus
prior to individual master starting the operation (SPI Cycle In Progress
a.k.a SCIP bit represents the status of SPI operation on individual
master).

Thus, any SPI operation triggered in multi-master environment might need
to account a worst case scenario where the most time consuming operation
might have occupied the SPI bus from a master and an operation initiated
by another master just timed out.

Here is the timeout calculation for any hardware sequencing operation:
  Worst Case Operational Delay =
        (Maximum Time consumed by a SPI operation + Any marginal
                     adjustment)

Timeout Recommendation for Hardware Sequencing Operation =
        ((Worst Case Operational Delay) * (#No. Of SPI Master - 1) +
                        Current Operational latency)

Assume, on Intel platform with 6 SPI master like, Host CPU, CSE, EC,
GbE and other reserved etc, hence, the Timeout Calculation for SPI
erase Operation would look like as below:

Maximum Time consumed by a SPI Operation =  5 seconds

Worst Case Operational Delay = 5 seconds

Timeout Recommendation for Hardware Seq Operation =
             5 seconds * (6 - 1) + 5 seconds = 30 seconds

BUG=b:223630977
TEST=Able to perform read/write/erase operation on PCH 600 series
chipset (board name: Brya).

Original-Signed-off-by: Subrata Banik 
Original-Reviewed-on: https://review.coreboot.org/c/flashrom/+/62867
Original-Tested-by: build bot (Jenkins) 
Original-Reviewed-by: Anastasia Klimchuk 
Original-Reviewed-by: Arthur Heymans 
Original-Reviewed-by: Edward O'Callaghan 
Change-Id: Ifa910dea794175d8ee2ad277549e5a0d69cba45b
Signed-off-by: Felix Singer 
Reviewed-on: https://review.coreboot.org/c/flashrom/+/68691
Tested-by: build bot (Jenkins) 
Reviewed-by: Michael Niewöhner 
---
M ichspi.c
1 file changed, 87 insertions(+), 11 deletions(-)

Approvals:
  build bot (Jenkins): Verified
  Michael Niewöhner: Looks good to me, approved

diff --git a/ichspi.c b/ichspi.c
index 12ee126..725bfb3 100644
--- a/ichspi.c
+++ b/ichspi.c
@@ -1282,20 +1282,24 @@
    Resets all error flags in HSFS.
    Returns 0 if the cycle completes successfully without errors within
    timeout us, 1 on errors. */
-static int ich_hwseq_wait_for_cycle_complete(unsigned int timeout,
-					     unsigned int len)
+static int ich_hwseq_wait_for_cycle_complete(unsigned int len)
 {
+	/*
+	 * The SPI bus may be busy due to performing operations from other masters, hence
+	 * introduce the long timeout of 30s to cover the worst case scenarios as well.
+	 */
+	unsigned int timeout_us = 30 * 1000 * 1000;
    uint16_t hsfs;
    uint32_t addr;

-	timeout /= 8; /* scale timeout duration to counter */
+	timeout_us /= 8; /* scale timeout duration to counter */
    while ((((hsfs = REGREAD16(ICH9_REG_HSFS)) &
    	 (HSFS_FDONE | HSFS_FCERR)) == 0) &&
-	       --timeout) {
+	       --timeout_us) {
    	programmer_delay(8);
    }
    REGWRITE16(ICH9_REG_HSFS, REGREAD16(ICH9_REG_HSFS));
-	if (!timeout) {
+	if (!timeout_us) {
    	addr = REGREAD32(ICH9_REG_FADDR) & hwseq_data.addr_mask;
    	msg_perr("Timeout error between offset 0x%08x and "
    		 "0x%08x (= 0x%08x + %d)!\n",
@@ -1378,7 +1382,6 @@
 {
    uint32_t erase_block;
    uint16_t hsfc;
-	uint32_t timeout = 5000 * 1000; /* 5 s for max 64 kB */

erase_block = ich_hwseq_get_erase_block_size(addr);
    if (len != erase_block) {
@@ -1418,7 +1421,7 @@
    prettyprint_ich9_reg_hsfc(hsfc);
    REGWRITE16(ICH9_REG_HSFC, hsfc);

-	if (ich_hwseq_wait_for_cycle_complete(timeout, len))
+	if (ich_hwseq_wait_for_cycle_complete(len))
    	return -1;
    return 0;
 }
@@ -1427,7 +1430,6 @@
    		  unsigned int addr, unsigned int len)
 {
    uint16_t hsfc;
-	uint16_t timeout = 100 * 60;
    uint8_t block_len;

if (addr + len > flash->chip->total_size * 1024) {
@@ -1455,7 +1457,7 @@
    	hsfc |= HSFC_FGO; /* start */
    	REGWRITE16(ICH9_REG_HSFC, hsfc);

-		if (ich_hwseq_wait_for_cycle_complete(timeout, block_len))
+		if (ich_hwseq_wait_for_cycle_complete(block_len))
    		return 1;
    	ich_read_data(buf, block_len, ICH9_REG_FDATA0);
    	addr += block_len;
@@ -1468,7 +1470,6 @@
 static int ich_hwseq_write(struct flashctx *flash, const uint8_t *buf, unsigned int addr, unsigned int len)
 {
    uint16_t hsfc;
-	uint16_t timeout = 100 * 60;
    uint8_t block_len;

if (addr + len > flash->chip->total_size * 1024) {
@@ -1497,7 +1498,7 @@
    	hsfc |= HSFC_FGO; /* start */
    	REGWRITE16(ICH9_REG_HSFC, hsfc);

-		if (ich_hwseq_wait_for_cycle_complete(timeout, block_len))
+		if (ich_hwseq_wait_for_cycle_complete(block_len))
    		return -1;
    	addr += block_len;
    	buf += block_len;