hw/i2c: pmbus: reset page register for out of range reads

The linux pmbus driver scans all possible pages and does not reset the
current page after the scan, making all future page reads fail as out of range
on devices with a single page.

This change resets out of range pages immediately on write.

Also added a qtest for simultaneous writes to all pages.

Reviewed-by: Hao Wu <wuhaotsh@google.com>
Signed-off-by: Titus Rwantare <titusr@google.com>
Message-ID: <20231023-staging-pmbus-v3-v4-8-07a8cb7cd20a@google.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

hw/i2c/pmbus_device.c

@@ -1255,6 +1255,15 @@ static int pmbus_write_data(SMBusDevice *smd, uint8_t *buf, uint8_t len)
 
     if (pmdev->code == PMBUS_PAGE) {
         pmdev->page = pmbus_receive8(pmdev);
+
+        if (pmdev->page > pmdev->num_pages - 1 && pmdev->page != PB_ALL_PAGES) {
+            qemu_log_mask(LOG_GUEST_ERROR,
+                          "%s: page %u is out of range\n",
+                          __func__, pmdev->page);
+            pmdev->page = 0; /* undefined behaviour - reset to page 0 */
+            pmbus_cml_error(pmdev);
+            return PMBUS_ERR_BYTE;
+        }
         return 0;
     }
 
@@ -1268,15 +1277,6 @@ static int pmbus_write_data(SMBusDevice *smd, uint8_t *buf, uint8_t len)
         return 0;
     }
 
-    if (pmdev->page > pmdev->num_pages - 1) {
-        qemu_log_mask(LOG_GUEST_ERROR,
-                        "%s: page %u is out of range\n",
-                        __func__, pmdev->page);
-        pmdev->page = 0; /* undefined behaviour - reset to page 0 */
-        pmbus_cml_error(pmdev);
-        return PMBUS_ERR_BYTE;
-    }
-
     index = pmdev->page;
 
     switch (pmdev->code) {

tests/qtest/max34451-test.c

@@ -18,6 +18,7 @@
 #define TEST_ID "max34451-test"
 #define TEST_ADDR (0x4e)
 
+#define MAX34451_MFR_MODE               0xD1
 #define MAX34451_MFR_VOUT_PEAK          0xD4
 #define MAX34451_MFR_IOUT_PEAK          0xD5
 #define MAX34451_MFR_TEMPERATURE_PEAK   0xD6
@@ -315,6 +316,28 @@ static void test_ot_faults(void *obj, void *data, QGuestAllocator *alloc)
     }
 }
 
+#define RAND_ON_OFF_CONFIG  0x12
+#define RAND_MFR_MODE       0x3456
+
+/* test writes to all pages */
+static void test_all_pages(void *obj, void *data, QGuestAllocator *alloc)
+{
+    uint16_t i2c_value;
+    QI2CDevice *i2cdev = (QI2CDevice *)obj;
+
+    i2c_set8(i2cdev, PMBUS_PAGE, PB_ALL_PAGES);
+    i2c_set8(i2cdev, PMBUS_ON_OFF_CONFIG, RAND_ON_OFF_CONFIG);
+    max34451_i2c_set16(i2cdev, MAX34451_MFR_MODE, RAND_MFR_MODE);
+
+    for (int i = 0; i < MAX34451_NUM_TEMP_DEVICES + MAX34451_NUM_PWR_DEVICES;
+         i++) {
+        i2c_value = i2c_get8(i2cdev, PMBUS_ON_OFF_CONFIG);
+        g_assert_cmphex(i2c_value, ==, RAND_ON_OFF_CONFIG);
+        i2c_value = max34451_i2c_get16(i2cdev, MAX34451_MFR_MODE);
+        g_assert_cmphex(i2c_value, ==, RAND_MFR_MODE);
+    }
+}
+
 static void max34451_register_nodes(void)
 {
     QOSGraphEdgeOptions opts = {
@@ -332,5 +355,6 @@ static void max34451_register_nodes(void)
     qos_add_test("test_ro_regs", "max34451", test_ro_regs, NULL);
     qos_add_test("test_ov_faults", "max34451", test_ov_faults, NULL);
     qos_add_test("test_ot_faults", "max34451", test_ot_faults, NULL);
+    qos_add_test("test_all_pages", "max34451", test_all_pages, NULL);
 }
 libqos_init(max34451_register_nodes);