linux-kernel - Re: [PATCH] sata_nv: fix for completion handling

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Message-ID: <47A34DEC.7050808@garzik.org>
Date:	Fri, 01 Feb 2008 11:50:52 -0500
From:	Jeff Garzik <jeff@...zik.org>
To:	Robert Hancock <hancockr@...w.ca>
CC:	linux-kernel <linux-kernel@...r.kernel.org>,
	ide <linux-ide@...r.kernel.org>, Tejun Heo <htejun@...il.com>,
	Kuan Luo <kluo@...dia.com>, Allen Martin <AMartin@...dia.com>
Subject: Re: [PATCH] sata_nv: fix for completion handling

Robert Hancock wrote:
> This patch is based on an original patch from Kuan Luo of NVIDIA,
> posted under subject "fixed a bug of adma in rhel4u5 with HDS7250SASUN500G".
> His description follows. I've reworked it a bit to avoid some unnecessary
> repeated checks but it should be functionally identical.
> 
> "The patch is to solve the error message "ata1: CPB flags CMD err,
> flags=0x11" when testing HDS7250SASUN500G in rhel4u5.
> I tested this hd in 2.6.24-rc7 which needed to remove the mask in
> blacklist to run the ncq and the same error also showed up. 
> 
> I traced the  bug and found that the interrupt finished a command (for
> example, tag=0) when the driver got that adma status is
> NV_ADMA_STAT_DONE  and  cpb->resp_flags is NV_CPB_RESP_DONE.
> However, For this hd, the drive maybe didn't clear bit 0 at this moment.
> It meaned the hardware  had not completely finished the command.
> If at the same time  the driver freed the command(tag 0) and sended
> another command (tag 0), the error happened.
> 
> The notifier register is 32-bit register containing notifier value.
> Value is bit vector containing one bit per tag number (0-31) in
> corresponding bit positions (bit 0 is for tag 0, etc). When bit is set
> then ADMA indicates that command with corresponding tag number completed
> execution.
> 
> So i added the check notifier code. Sometimes i saw that the notifier
> reg set some bits  , but the adma status set NV_ADMA_STAT_CMD_COMPLETE
> ,not NV_ADMA_STAT_DONE. So i added the NV_ADMA_STAT_CMD_COMPLETE check
> code."
> 
> Signed-off-by: Robert Hancock <hancockr@...w.ca>

applied, thanks all for investigating this stuff



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