On Fri, Feb 18, 2022 at 02:33:48PM +0100, Jan Dabros wrote:
> Kernel test robot reported incorrect type in argument 1 of readl(), but
> more importantly it brought attention that MMIO accessor shouldn't be
> used in this case, since req->hdr.status is part of a command-response
> buffer in system memory.
>
> Since its value may be altered by PSP outside of the scope of current
> thread (somehow similar to IRQ handler case), we need to use
> READ_ONCE() to ensure compiler won't optimize this call.
>
> Fix also 'status' variable type to reflect that corresponding field in
> command-response buffer is platform-independent u32.
Thanks for the fix, seems reasonable to me.
Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> Signed-off-by: Jan Dabros <jsd@xxxxxxxxxxxx>
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> ---
> drivers/i2c/busses/i2c-designware-amdpsp.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-designware-amdpsp.c b/drivers/i2c/busses/i2c-designware-amdpsp.c
> index 752e0024db03..c64e459afb5c 100644
> --- a/drivers/i2c/busses/i2c-designware-amdpsp.c
> +++ b/drivers/i2c/busses/i2c-designware-amdpsp.c
> @@ -160,9 +160,10 @@ static int psp_send_cmd(struct psp_i2c_req *req)
> /* Helper to verify status returned by PSP */
> static int check_i2c_req_sts(struct psp_i2c_req *req)
> {
> - int status;
> + u32 status;
>
> - status = readl(&req->hdr.status);
> + /* Status field in command-response buffer is updated by PSP */
> + status = READ_ONCE(req->hdr.status);
>
> switch (status) {
> case PSP_I2C_REQ_STS_OK:
> --
> 2.35.1.265.g69c8d7142f-goog
>
--
With Best Regards,
Andy Shevchenko
