kernel/linux.git/drivers/mailbox/pcc.c, branch v6.18.21

mailbox: pcc: Remove spurious IRQF_ONESHOT usage

2026-03-04T12:20:29+00:00

[ Upstream commit 673327028cd61db68a1e0c708be2e302c082adf9 ] The PCC code currently specifies IRQF_ONESHOT if the interrupt could potentially be shared but doesn't actually use request_threaded_irq() and the interrupt handler does not use IRQ_WAKE_THREAD so IRQF_ONESHOT is never relevant. Since commit aef30c8d569c ("genirq: Warn about using IRQF_ONESHOT without a threaded handler") specifying it has resulted in a WARN_ON(), fix this by removing IRQF_ONESHOT. Reported-by: Aishwarya TCV Signed-off-by: Mark Brown Reviewed-by: Sudeep Holla Signed-off-by: Jassi Brar Signed-off-by: Sasha Levin

Revert "mailbox/pcc: support mailbox management of the shared buffer"

2026-02-26T22:59:28+00:00

[ Upstream commit f82c3e62b6b8c31d8c56415bf38658f306fda4cb ] This reverts commit 5378bdf6a611a32500fccf13d14156f219bb0c85. Commit 5378bdf6a611 ("mailbox/pcc: support mailbox management of the shared buffer") attempted to introduce generic helpers for managing the PCC shared memory, but it largely duplicates functionality already provided by the mailbox core and leaves gaps: 1. TX preparation: The mailbox framework already supports this via ->tx_prepare callback for mailbox clients. The patch adds pcc_write_to_buffer() and expects clients to toggle pchan->chan.manage_writes, but no drivers set manage_writes, so pcc_write_to_buffer() has no users. 2. RX handling: Data reception is already delivered through mbox_chan_received_data() and client ->rx_callback. The patch adds an optional pchan->chan.rx_alloc, which again has no users and duplicates the existing path. 3. Completion handling: While adding last_tx_done is directionally useful, the implementation only covers Type 3/4 and fails to handle the absence of a command_complete register, so it is incomplete for other types. Given the duplication and incomplete coverage, revert this change. Any new requirements should be addressed in focused follow-ups rather than bundling multiple behavioral changes together. Fixes: 5378bdf6a611 ("mailbox/pcc: support mailbox management of the shared buffer") Signed-off-by: Sudeep Holla Signed-off-by: Jassi Brar Signed-off-by: Sasha Levin

mailbox: pcc: don't zero error register

2025-11-28T15:31:53+00:00

The error status mask for a type 3/4 subspace is used for reading the error status, and the bitwise inverse is used for clearing the error with the intent being to preserve any of the non-error bits. However, we were previously applying the mask to extract the status and then applying the inverse to the result which ended up clearing all bits. Instead, store the inverse mask in the preserve mask and then use that on the original value read from the error status so that only the error is cleared. Fixes: c45ded7e1135 ("mailbox: pcc: Add support for PCCT extended PCC subspaces(type 3/4)") Signed-off-by: Jamie Iles Signed-off-by: Punit Agrawal Signed-off-by: Jassi Brar

mailbox/pcc: support mailbox management of the shared buffer

2025-08-08T04:49:56+00:00

Define a new, optional, callback that allows the driver to specify how the return data buffer is allocated. If that callback is set, mailbox/pcc.c is now responsible for reading from and writing to the PCC shared buffer. This also allows for proper checks of the Commnand complete flag between the PCC sender and receiver. For Type 4 channels, initialize the command complete flag prior to accepting messages. Since the mailbox does not know what memory allocation scheme to use for response messages, the client now has an optional callback that allows it to allocate the buffer for a response message. When an outbound message is written to the buffer, the mailbox checks for the flag indicating the client wants an tx complete notification via IRQ. Upon receipt of the interrupt It will pair it with the outgoing message. The expected use is to free the kernel memory buffer for the previous outgoing message. Signed-off-by: Adam Young Signed-off-by: Jassi Brar

mailbox: pcc: Refactor and simplify check_and_ack()

2025-03-27T01:58:26+00:00

The existing check_and_ack() function had unnecessary complexity. The logic could be streamlined to improve code readability and maintainability. The command update register needs to be updated in order to acknowledge the platform notification through type 4 channel. So it can be done unconditionally. Currently it is complicated just to make use of pcc_send_data() which also executes the same updation. In order to simplify, let us just ring the doorbell directly from check_and_ack() instead of calling into pcc_send_data(). While at it, rename it into pcc_chan_check_and_ack() to maintain consistency in the driver. Acked-by: Huisong Li Tested-by: Adam Young Signed-off-by: Sudeep Holla Signed-off-by: Jassi Brar

mailbox: pcc: Always map the shared memory communication address

2025-03-27T01:58:26+00:00

Currently the shared memory communication address was mapped by the mailbox client drivers leading to all sorts of inconsistencies. It also has resulted in the inconsistent attributes used while mapping the shared memory regions. In order to remove/eliminate any issues, let us ensures the shared memory address is always mapped and unmapped when the PCC channels are requested and release. We need to map them as the ACPI PCCT associates these shared memory with each channel subspace and may need use the status or the flags in the headers of those shared memory communication address regions to manage the transport/channel. Note, until all the drivers using PCC start using this mapped shmem, there might be double mapping of the shared memory address. This shouldn't have any impact on existing mbox client drivers. Since there are no users of pcc_chan_ioremap() and also it is mapped by default, we can stop exporting it and merge the functionality into pcc_mbox_request_channel(). Acked-by: Huisong Li Tested-by: Huisong Li Tested-by: Adam Young Signed-off-by: Sudeep Holla Signed-off-by: Jassi Brar

mailbox: pcc: Refactor error handling in irq handler into separate function

2025-03-27T01:58:26+00:00

The existing error handling logic in pcc_mbox_irq() is intermixed with the main flow of the function. The command complete check and the complete complete update/acknowledgment are nicely factored into separate functions. Moves error detection and clearing logic into a separate function called: pcc_mbox_error_check_and_clear() by extracting error-handling logic from pcc_mbox_irq(). This ensures error checking and clearing are handled separately and it improves maintainability by keeping the IRQ handler focused on processing events. Acked-by: Huisong Li Tested-by: Huisong Li Tested-by: Adam Young Signed-off-by: Sudeep Holla Signed-off-by: Jassi Brar

mailbox: pcc: Use acpi_os_ioremap() instead of ioremap()

2025-03-27T01:58:26+00:00

The Platform Communication Channel (PCC) mailbox driver currently uses ioremap() to map channel shared memory regions. However it is preferred to use acpi_os_ioremap(), which is mapping function specific to EFI/ACPI defined memory regions. It ensures that the correct memory attributes are applied when mapping ACPI-provided regions. While at it, also add checks for handling any errors with the mapping. Acked-by: Huisong Li Tested-by: Huisong Li Tested-by: Adam Young Signed-off-by: Sudeep Holla Signed-off-by: Jassi Brar

mailbox: pcc: Return early if no GAS register from pcc_mbox_cmd_complete_check

2025-03-27T01:58:25+00:00

pcc_mbox_cmd_complete_check() accesses pchan->cmd_complete.gas to check command completion status. Even if GAS is NULL, pcc_chan_reg_read() gets called which returns success doing nothing and then we return. Add an early return if pchan->cmd_complete.gas == NULL before performing any operations. Acked-by: Huisong Li Tested-by: Huisong Li Tested-by: Adam Young Signed-off-by: Sudeep Holla Signed-off-by: Jassi Brar

mailbox: pcc: Drop unnecessary endianness conversion of pcc_hdr.flags

2025-03-27T01:58:25+00:00

The Sparse static checker flags a type mismatch warning related to endianness conversion: | warning: incorrect type in argument 1 (different base types) | expected restricted __le32 const [usertype] *p | got unsigned int * This is because an explicit endianness conversion (le32_to_cpu()) was applied unnecessarily to a pcc_hdr.flags field that is already in little-endian format. The PCC driver is only enabled on little-endian kernels due to its dependency on ACPI and EFI, making the explicit conversion unnecessary. The redundant conversion occurs in pcc_chan_check_and_ack() for the pcc_hdr.flags field. Drop this unnecessary endianness conversion of pcc_hdr.flags. Also drop the redundant PCC_ACK_FLAG_MASK definition and use the more appropriate and already defined PCC_CMD_COMPLETION_NOTIFY. Acked-by: Huisong Li Tested-by: Adam Young Signed-off-by: Sudeep Holla Signed-off-by: Jassi Brar