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hw/i2c: pmbus: Page #255 is valid page for read requests.

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Current implementation of the pmbus core driver treats the read request
for page 255 as invalid request and sets the invalid command bit (bit 7)
in the STATUS_CML register. As per the PMBus specification it is a valid
request.

Refer to the PMBus specification, revision 1.3.1, section 11.10 PAGE,
on the page 58:
  "Setting the PAGE to FFh means that all subsequent comands are to be
   applied to all outputs.

   Some commands, such as READ_TEMPERATURE, may use a common sensor but
   be available on all pages of a device. Such implementations are the
   decision of each device manufacturer or are specified in a PMBus
   Application Profile. Consult the manufacturer's documents or the
   Application Profile Specification as needed."

For e.g.,
The VOUT_MODE is a valid command for page 255 for maxim 31785 device.
refer to Table 1. PMBus Command Codes on page 14 in the datasheet.
https://datasheets.maximintegrated.com/en/ds/MAX31785.pdf

Fixes: 38870253f1 ("hw/i2c: pmbus: fix error returns and guard against out of range accesses")

Signed-off-by: Maheswara Kurapati <quic_mkurapat@quicinc.com>
Signed-off-by: Jae Hyun Yoo <quic_jaehyoo@quicinc.com>
Reviewed-by: Titus Rwantare <titusr@google.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20220627154703.148943-4-quic_jaehyoo@quicinc.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
This commit is contained in:
Maheswara Kurapati 2022-06-30 09:21:13 +02:00 committed by Cédric Le Goater
parent ece4cccd67
commit dd0b3271e5
1 changed files with 1 additions and 5 deletions
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6
hw/i2c/pmbus_device.c
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@ -284,14 +284,10 @@ static uint8_t pmbus_receive_byte(SMBusDevice *smd)
/* /*
* Reading from all pages will return the value from page 0, * Reading from all pages will return the value from page 0,
* this is unspecified behaviour in general. * means that all subsequent commands are to be applied to all output.
*/ */
if (pmdev->page == PB_ALL_PAGES) { if (pmdev->page == PB_ALL_PAGES) {
index = 0; index = 0;
qemu_log_mask(LOG_GUEST_ERROR,
"%s: tried to read from all pages\n",
__func__);
pmbus_cml_error(pmdev);
} else if (pmdev->page > pmdev->num_pages - 1) { } else if (pmdev->page > pmdev->num_pages - 1) {
qemu_log_mask(LOG_GUEST_ERROR, qemu_log_mask(LOG_GUEST_ERROR,
"%s: page %d is out of range\n", "%s: page %d is out of range\n",