Re: [PATCH 1/1] PCI/DOE: adjust data object length

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Wed,  9 Nov 2022 10:20:44 +0800
Li Ming <ming4.li@intel.com> wrote:

> The value of data object length 0x0 indicates 2^18 dwords being
> transferred, it is introduced in PCIe r6.0,sec 6.30.1. This patch

Was introduced prior to that in the DOE ECN, so perhaps just drop "introduced".

I'm not sure why we missed that little detail of the spec originally so good to fix this up.
Probably deserves a fixes tag though it would be very hard to hit
with the only protocol we currently have upstream.

Other than what Bjorn pointed out and the missing bracket the
Robot found, looks good to me.

> adjusts the value of data object length for the above case on both
> sending side and receiving side.
> 
> Besides, it is unnecessary to check whether length is greater than
> SZ_1M while receiving a response data object, because length from LENGTH
> field of data object header, max value is 2^18.
> 
> Signed-off-by: Li Ming <ming4.li@intel.com>
> ---
>  drivers/pci/doe.c | 21 +++++++++++++++++----
>  1 file changed, 17 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/doe.c b/drivers/pci/doe.c
> index e402f05068a5..204cbc570f63 100644
> --- a/drivers/pci/doe.c
> +++ b/drivers/pci/doe.c
> @@ -29,6 +29,9 @@
>  #define PCI_DOE_FLAG_CANCEL	0
>  #define PCI_DOE_FLAG_DEAD	1
>  
> +/* Max data object length is 2^18 dwords */
> +#define PCI_DOE_MAX_LENGTH	(2 << 18)
> +
>  /**
>   * struct pci_doe_mb - State for a single DOE mailbox
>   *
> @@ -107,6 +110,7 @@ static int pci_doe_send_req(struct pci_doe_mb *doe_mb,
>  {
>  	struct pci_dev *pdev = doe_mb->pdev;
>  	int offset = doe_mb->cap_offset;
> +	u32 length;
>  	u32 val;
>  	int i;
>  
> @@ -128,10 +132,12 @@ static int pci_doe_send_req(struct pci_doe_mb *doe_mb,
>  		FIELD_PREP(PCI_DOE_DATA_OBJECT_HEADER_1_TYPE, task->prot.type);
>  	pci_write_config_dword(pdev, offset + PCI_DOE_WRITE, val);
>  	/* Length is 2 DW of header + length of payload in DW */
> +	length = 2 + task->request_pl_sz / sizeof(u32);
> +	if (length == PCI_DOE_MAX_LENGTH)
> +		length = 0;
>  	pci_write_config_dword(pdev, offset + PCI_DOE_WRITE,
>  			       FIELD_PREP(PCI_DOE_DATA_OBJECT_HEADER_2_LENGTH,
> -					  2 + task->request_pl_sz /
> -						sizeof(u32)));
> +					  length);
>  	for (i = 0; i < task->request_pl_sz / sizeof(u32); i++)
>  		pci_write_config_dword(pdev, offset + PCI_DOE_WRITE,
>  				       task->request_pl[i]);
> @@ -178,7 +184,10 @@ static int pci_doe_recv_resp(struct pci_doe_mb *doe_mb, struct pci_doe_task *tas
>  	pci_write_config_dword(pdev, offset + PCI_DOE_READ, 0);
>  
>  	length = FIELD_GET(PCI_DOE_DATA_OBJECT_HEADER_2_LENGTH, val);
> -	if (length > SZ_1M || length < 2)
> +	/* A value of 0x0 indicates max data object length */
> +	if (!length)
> +		length = PCI_DOE_MAX_LENGTH;
> +	if (length < 2)
>  		return -EIO;
>  
>  	/* First 2 dwords have already been read */
> @@ -520,8 +529,12 @@ int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
>  	/*
>  	 * DOE requests must be a whole number of DW and the response needs to
>  	 * be big enough for at least 1 DW
> +	 *
> +	 * Max data object length is 1MB, and data object header occupies 8B,
> +	 * thus request_pl_sz should not be greater than 1MB - 8B.
>  	 */
> -	if (task->request_pl_sz % sizeof(u32) ||
> +	if (task->request_pl_sz > SZ_1M - 8 ||
> +	    task->request_pl_sz % sizeof(u32) ||
>  	    task->response_pl_sz < sizeof(u32))
>  		return -EINVAL;
>