[net-next,2/4] cxgb4: For T4, don't read the Firmware Mailbox Control register

T4 doesn't have the Shadow copy of the register which we can read without
side effect. So don't read mbox control register for T4 adapter

Signed-off-by: Hariprasad Shenai <hariprasad@chelsio.com>
---
 drivers/net/ethernet/chelsio/cxgb4/cxgb4_debugfs.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

Hello.

On 09/30/2015 05:24 PM, Hariprasad Shenai wrote:

> T4 doesn't have the Shadow copy of the register which we can read without
> side effect. So don't read mbox control register for T4 adapter
>
> Signed-off-by: Hariprasad Shenai <hariprasad@chelsio.com>
> ---
>   drivers/net/ethernet/chelsio/cxgb4/cxgb4_debugfs.c | 18 +++++++++++++-----
>   1 file changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/ethernet/chelsio/cxgb4/cxgb4_debugfs.c b/drivers/net/ethernet/chelsio/cxgb4/cxgb4_debugfs.c
> index 0a87a32..c20b41c 100644
> --- a/drivers/net/ethernet/chelsio/cxgb4/cxgb4_debugfs.c
> +++ b/drivers/net/ethernet/chelsio/cxgb4/cxgb4_debugfs.c
> @@ -1134,12 +1134,20 @@ static int mbox_show(struct seq_file *seq, void *v)
>   	unsigned int mbox = (uintptr_t)seq->private & 7;
>   	struct adapter *adap = seq->private - mbox;
>   	void __iomem *addr = adap->regs + PF_REG(mbox, CIM_PF_MAILBOX_DATA_A);
> -	unsigned int ctrl_reg = (is_t4(adap->params.chip)
> -				 ? CIM_PF_MAILBOX_CTRL_A
> -				 : CIM_PF_MAILBOX_CTRL_SHADOW_COPY_A);
> -	void __iomem *ctrl = adap->regs + PF_REG(mbox, ctrl_reg);
>
> -	i = MBOWNER_G(readl(ctrl));
> +	/* For T4 we don't have a shadow copy of the Mailbox Control register.
> +	 * And since reading that real register causes a side effect of
> +	 * granting ownership, we're best of simply not reading it at all.
> +	 */
> +	if (is_t4(adap->params.chip))
> +		i = 4; /* index of "<unread>" */

    The kernel CodingStyle dictates that you should enclose all branches in {} 
if at least one branch has it.

> +	else {
> +		unsigned int ctrl_reg = CIM_PF_MAILBOX_CTRL_SHADOW_COPY_A;
> +		void __iomem *ctrl = adap->regs + PF_REG(mbox, ctrl_reg);
> +
> +		i = MBOWNER_G(readl(ctrl));
> +	}
> +
>   	seq_printf(seq, "mailbox owned by %s\n\n", owner[i]);
>
>   	for (i = 0; i < MBOX_LEN; i += 8)

MBR, Sergei

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