Hi, -----Original Message----- From: Sergei Shtylyov [mailto:sshtylyov@xxxxxxxxxx] Sent: Thursday, December 29, 2011 10:10 PM To: Zhang, Sonic Cc: Sergei Shtylyov; linux-ide@xxxxxxxxxxxxxxx; jgarzik@xxxxxxxxx Subject: Re: [PATCH] pata_bf54x: fix BMIDE status register emulation Hello. On 12/29/2011 02:31 PM, Zhang, Sonic wrote: > Acked-by: Sonic Zhang<sonic.zhang@xxxxxxxxxx> > SG list was not implemented in pata_bf54x driver from the beginning, because ATAPI controller on BF54x support maximum 131070 bytes in one BMDMA transfer. So what? You can chain transfers in software, using "done" interrupts I think... Sonic> I just figure out that this can be solved by setting the max sg_tablesize to 4. > The size in sg list buffers may exceeds this limitation easily. Do you know a way to set the maximum total buffer size in a sg list? Maybe thru 'max_sectors' field in scsi_host_template? Though sectors can be of different size... Sonic> max_sectors doesn't affect the max size of a sg list. > Static struct scsi_host_template bfin_sht = { > ATA_BASE_SHT(DRV_NAME), > .sg_tablesize = SG_NONE, > .dma_boundary = ATA_DMA_BOUNDARY, > }; Ah, I have overlooked this. Anyway 'dma_boundary' should be twice more than ATA_DMA_BOUNDARY. Sonic> I don't find this boundary limit in the spec of the DMA controller for BF54x ATAPI device. So, it can be removed. > Sonic > -----Original Message----- > From: Sergei Shtylyov [mailto:sshtylyov@xxxxxxxxxxxxx] > Sent: Wednesday, December 28, 2011 11:37 PM > To: linux-ide@xxxxxxxxxxxxxxx; jgarzik@xxxxxxxxx; Zhang, Sonic > Subject: [PATCH] pata_bf54x: fix BMIDE status register emulation > The author of this driver clearly wasn't familiar with the BMIDE specification > (also known as SFF-8038i) when he implemented the bmdma_status() method: first, > the interrupt bit of the BMIDE status register corresponds to nothing else but > INTRQ signal (ATAPI_DEV_INT here); second, the error bit is only set if the > controller encounters issue doing the bus master transfers, not on the DMA burst > termination interrupts like here (moreover, setting the error bit doesn't cause > an interrupt). > (The only thing I couldn't figure out is how to flush the FIFO to memory once > the interrupt happens as required by the mentioned spec.) > Signed-off-by: Sergei Shtylyov<sshtylyov@xxxxxxxxxxxxx> > --- > The patch is against the current Linus' tree. > Sonic, if you still work in Analog Devices, please give this a try. > > I looked over the driver, and it left pretty bad impression. In particular, > I highly doubt that the transfers with more than one S/G item can work. And > this is after the driver has been in the kernel for 4 years already... > Unfortunately, I have neither hardware nor much time to work on improving it... WBR, Sergei -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
