linux-kernel - Re: [PATCH v1 01/20] [SCSI] mpt3sas: Added Combined Reply Queue feature to extend up-to 96 MSIX vector support

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Date:	Fri, 19 Jun 2015 10:57:44 -0400
From:	"Martin K. Petersen" <martin.petersen@...cle.com>
To:	Sreekanth Reddy <sreekanth.reddy@...gotech.com>
Cc:	jejb@...nel.org, hch@...radead.org, jthumshirn@...e.de,
	martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
	JBottomley@...allels.com, Sathya.Prakash@...gotech.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 01/20] [SCSI] mpt3sas: Added Combined Reply Queue feature to extend up-to 96 MSIX vector support

>>>>> "Sreekanth" == Sreekanth Reddy <sreekanth.reddy@...gotech.com> writes:

Sreekanth,

It's fine that you outline the 96 / 12 = 8 layout in the patch
description. But that relationship is not made clear when reading the
code. Please add a comment describing why things are set up this way.

> @@ -1009,8 +1009,15 @@ _base_interrupt(int irq, void *bus_id)
>  	}
>  
>  	wmb();
> -	writel(reply_q->reply_post_host_index | (msix_index <<
> -	    MPI2_RPHI_MSIX_INDEX_SHIFT), &ioc->chip->ReplyPostHostIndex);
> +	if (ioc->msix96_vector) {
> +		writel(reply_q->reply_post_host_index | ((msix_index  & 7) <<
> +			MPI2_RPHI_MSIX_INDEX_SHIFT),
> +				ioc->replyPostRegisterIndex[msix_index/8]);
> +	} else {
> +		writel(reply_q->reply_post_host_index | (msix_index <<
> +			MPI2_RPHI_MSIX_INDEX_SHIFT),
> +				&ioc->chip->ReplyPostHostIndex);
> +	}

Too many brackets. Why don't you do:

	index = reply_q->reply_post_host_index |
		((msix_index & 7) << MPI_RPHI_MSIX_INDEX_SHIFT);

	if (ioc->msix96_vector)
		writel(index, ioc->replyPostRegisterIndex[msix_index / 8]);
	else
        	writel(index, &ioc->chip->ReplyPostHostIndex);

> +	if (ioc->msix96_vector && ioc->reply_queue_count > 8) {
> +		/* If this is an 96 vector supported device,
> +		set up ReplyPostIndex addresses */

Bad comment formatting.

> +		ioc->replyPostRegisterIndex = kcalloc(12,
> +			sizeof(resource_size_t *), GFP_KERNEL);
[...]
> +		for (i = 0; i < 12; i++) {

Make 12 a constant or at the very least a variable with a comment.

> +			ioc->replyPostRegisterIndex[i] = (resource_size_t *)
> +				((u8 *)&ioc->chip->Doorbell +
> +				MPI25_SUP_REPLY_POST_HOST_INDEX_OFFSET +
> +				(i * 0x10));

0x10 - Another magic constant.

> @@ -4522,8 +4554,16 @@ _base_make_ioc_operational(struct MPT3SAS_ADAPTER *ioc, int sleep_flag)
>  
>  	/* initialize reply post host index */
>  	list_for_each_entry(reply_q, &ioc->reply_queue_list, list) {
> -		writel(reply_q->msix_index << MPI2_RPHI_MSIX_INDEX_SHIFT,
> -		    &ioc->chip->ReplyPostHostIndex);
> +		if (ioc->msix96_vector) {
> +			writel((reply_q->msix_index & 7)<<
> +			   MPI2_RPHI_MSIX_INDEX_SHIFT,
> +			   ioc->replyPostRegisterIndex[reply_q->msix_index/8]);
> +		} else {
> +			writel(reply_q->msix_index <<
> +				MPI2_RPHI_MSIX_INDEX_SHIFT,
> +					&ioc->chip->ReplyPostHostIndex);
> +		}
> +

Too many brackets.

-- 
Martin K. Petersen	Oracle Linux Engineering
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