FW: PMP hot plug issue in kernel

FW: PMP hot plug issue in kernel

[Bhartiya Anju-B07263]

 
	 Hi All,

		 
		Recently came across an issue which is decribed below.
		 
		Setup: Port Multiplier with 2 HDD's connected to it;
Port multiplier is connected to a SATA port of the Host Controller.
		 
		Test: HDD1 is mounted and using dd command a file of
size 512MB is being written on it.
		Command: time sh -c "dd if=/dev/zero of=/mnt/hd/ddfile
bs=1k count=512000 && sync"
		 
		While this command is running, if the second HDD on PMP
is plugged out, the R/W speed of the first HDD gets affected.
		Please see the results of experiments on 2.6.31 kernel.
		 
		Plug Out	 	 	
		real    0m34.433s
		user    0m0.932s
		sys     0m21.352s	 

		Plug in
		real    0m23.726s
		user    0m0.908s
		sys     0m21.388s	 

		Normal
		real    0m23.329s
		user    0m1.132s
		sys     0m20.968s	
		 
		The results are similiar with multiple Port Multipliers
(Si3726, Si4726 and EXAR PMP) and multiple Host controllers (Si3132  and
sata_fsl).
		 
		As the behaviour with multiple Host controllers and Port
Multipliers is the same so this seems to be an issue with libata stack.
		Is there already a patch for this issue? Any pointers or
help to fix this will be greatly appreciated.
		 
		Best Regards,
		Anju
		Applications Engineer 
		Freescale Semiconductor