[parisc-linux] Re: kernel>=2.6.4-rc3 hung or panic on C1[18]0

[Grant Grundler]

On Sat, Apr 24, 2004 at 08:52:37PM +0000, Joel Soete wrote:
> Hello Grant,
> 
> Sorry in advance to disturbe you with this c110 pb but if I well understand 
> the physical connection (fine doc find on openpa.net :) and better 
> understand what james means, otc I past the full last week to study more 
> ccio-dma and ncr53c8xx but I don't reach to locate the part of code making 
>  the link between those 2 part (i mean where ncr call ccio and visversa). 
>  Could you help me a bit more.

Yup. Using 2.6.5-pa8 source tree, ncr53c8xx.c calls DMA services from
ncr_scatter():

ncr53c8xx.c:7594:	u_long baddr = map_scsi_single_data(np, cmd);

sym53c8xx_comm.h:699:static int __map_scsi_sg_data(struct device *dev, Scsi_Cmnd *cmd)
...
sym53c8xx_comm.h:708:	use_sg = dma_map_sg(dev, cmd->buffer, cmd->use_sg, dma_dir);


asm/dma-mapping.h:91:static inline int
asm/dma-mapping.h:92:dma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
asm/dma-mapping.h:93:           enum dma_data_direction direction)
asm/dma-mapping.h:94:{
asm/dma-mapping.h:95:        return hppa_dma_ops->map_sg(dev, sg, nents, direction);
asm/dma-mapping.h:96:}

Then search for hppa_dma_ops in arch/parisc/kernel/* and drivers/parisc/*.c
to locate the various platform/chipset DMA support:

grundler <553>fgrep -n hppa_dma_ops arch/parisc/kernel/*c drivers/parisc/*
arch/parisc/kernel/drivers.c:30:struct hppa_dma_ops *hppa_dma_ops;
arch/parisc/kernel/drivers.c:31:EXPORT_SYMBOL(hppa_dma_ops);
arch/parisc/kernel/pci-dma.c:492:struct hppa_dma_ops pcxl_dma_ops = {
arch/parisc/kernel/pci-dma.c:533:struct hppa_dma_ops pcx_dma_ops = {
arch/parisc/kernel/setup.c:96:          hppa_dma_ops = &pcx_dma_ops;
arch/parisc/kernel/setup.c:101:         hppa_dma_ops = &pcxl_dma_ops;
drivers/parisc/ccio-dma.c:1009:static struct hppa_dma_ops ccio_ops = {
drivers/parisc/ccio-dma.c:1545: hppa_dma_ops = &ccio_ops;
drivers/parisc/ccio-rm-dma.c:183:       hppa_dma_ops = &ccio_ops;
drivers/parisc/sba_iommu.c:1177:static struct hppa_dma_ops sba_ops = {
drivers/parisc/sba_iommu.c:1809:        hppa_dma_ops = &sba_ops;

Ideally, "make" would detect when support for only one chipset is
needed and just do away with hppa_dma_ops completely (ie directly
call into the chipset specific function).

> Thanks in advance,
> 	Joel
> 
> PS: btw I noticed that ncr_attach() is still prefix by __init where 
> sym_attach() is now prefix by __devinit. I trust it is important but could 
> it be the simple reason of pb encounter?

IIRC, the difference is for hotplug.
__devinit section is preserved when CONFIG_HOTPLUG is enabled.
See linux/Documentation/pci.txt for the real description.

grant