Re: [PATCH v2 03/13] mailbox: pcc: Drop unnecessary endianness conversion of pcc_hdr.flags

lihuisong (C)
2025-03-11T11:20:00Z

在 2025/3/6 0:38, Sudeep Holla 写道:
> 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.
>
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> ---
> drivers/mailbox/pcc.c | 2 +-
> include/acpi/pcc.h | 1 -
> 2 files changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
> index 4c582fa2b8bf4c9a9368dba8220f567555dba963..42dd405482e407cf90e66917a46fb8e350e0eeaf 100644
> --- a/drivers/mailbox/pcc.c
> +++ b/drivers/mailbox/pcc.c
> @@ -292,7 +292,7 @@ static void check_and_ack(struct pcc_chan_info *pchan, struct mbox_chan *chan)
> *
> * The PCC master subspace channel clears chan_in_use to free channel.
> */
> - if (le32_to_cpup(&pcc_hdr.flags) & PCC_ACK_FLAG_MASK)
> + if (pcc_hdr.flags & PCC_CMD_COMPLETION_NOTIFY)
> pcc_send_data(chan, NULL);
> else
> pcc_chan_reg_read_modify_write(&pchan->cmd_update);
> diff --git a/include/acpi/pcc.h b/include/acpi/pcc.h
> index 699c1a37b8e7846362bae35477eb5736be15d79e..d1e506f041c5a80857d4a025fa3c1803746ba4b9 100644
> --- a/include/acpi/pcc.h
> +++ b/include/acpi/pcc.h
> @@ -32,7 +32,6 @@ struct pcc_mbox_chan {
> #define PCC_CMD_COMPLETION_NOTIFY BIT(0)
>
> #define MAX_PCC_SUBSPACES 256
> -#define PCC_ACK_FLAG_MASK 0x1
>
> #ifdef CONFIG_PCC
> extern struct pcc_mbox_chan *
Acked-by: Huisong Li <lihuisong@huawei.com>
>