linux-kernel - Re: [BUG 2.6.18] sata_promise unaligned PCI accesses on sparc64

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Message-id: <4516D5AC.20606@shaw.ca>
Date:	Sun, 24 Sep 2006 12:59:56 -0600
From:	Robert Hancock <hancockr@...w.ca>
To:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [BUG 2.6.18] sata_promise unaligned PCI accesses on sparc64

Mikael Pettersson wrote:
> The 2.6.18 kernel's sata_promise driver causes alignment
> traps in my Ultra5 sparc64 machine. dmesg shows:
> 
> SCSI subsystem initialized
> libata version 2.00 loaded.
> sata_promise 0000:02:03.0: version 1.04
> Kernel unaligned access at TPC[100a8cbc] pdc_ata_init_one+0x284/0x308 [sata_promise]
> Kernel unaligned access at TPC[100a8cd0] pdc_ata_init_one+0x298/0x308 [sata_promise]
> Kernel unaligned access at TPC[100a8cd4] pdc_ata_init_one+0x29c/0x308 [sata_promise]
> ata1: SATA max UDMA/133 cmd 0x1FF00008200 ctl 0x1FF00008238 bmdma 0x0 irq 18
> ata2: SATA max UDMA/133 cmd 0x1FF00008280 ctl 0x1FF000082B8 bmdma 0x0 irq 18
> scsi0 : sata_promise
> ata1: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
> ata1.00: ATA-6, max UDMA/133, 312581808 sectors: LBA48 NCQ (depth 0/32)
> ata1.00: configured for UDMA/133
> scsi1 : sata_promise
> ata2: SATA link down (SStatus 0 SControl 300)
>   Vendor: ATA       Model: ST3160827AS       Rev: 3.42
>   Type:   Direct-Access                      ANSI SCSI revision: 05
> 
> Using debug printk:s I've traced this to the three PDC_TBG_MODE
> accesses in sata_promise.c:pdc_host_init():
> 
> 	/* reduce TBG clock to 133 Mhz. */
> 	tmp = readl(mmio + PDC_TBG_MODE);
> 	tmp &= ~0x30000; /* clear bit 17, 16*/
> 	tmp |= 0x10000;  /* set bit 17:16 = 0:1 */
> 	writel(tmp, mmio + PDC_TBG_MODE);
> 
> 	readl(mmio + PDC_TBG_MODE);	/* flush */
> 
> The debugging printk:s also showed that mmio points to
> 0x000001ff00008000 and that PDC_TBG_MODE is 65, so mmio+PDC_TBG_MODE
> cannot possibly be 32-bit aligned.
> 
> From reading sata_promise.c it appears that PDC_TBG_MODE also
> intersects both PDC_INT_SEQMASK and PDC_FLASH_CTL, which I find weird.

Hmm.. Unaligned access to MMIO space doesn't seem like it would be a 
great idea on any platform.

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@...pamshaw.ca
Home Page: http://www.roberthancock.com/

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