[ofa-general] Re: [PATCH v2] RDMA/nes: Mitigate compatibility issue regarding PCI write credits

[Roland Dreier]

 > Under heavy load, there is an compatibility issue regarding PCI write
 > credits with certain chipsets.  It can be mitigated by limiting read
 > requests to 256 Bytes.

OK.

 > +module_param(limit_maxrdreqsz, int, 0644);

type can be bool instead of int here?

 > +	if ((limit_maxrdreqsz) ||
 > +		((nesdev->nesadapter->phy_type[0] == NES_PHY_TYPE_GLADIUS) &&
 > +		(hw_rev == NE020_REV1))) {
 > +		nes_debug(NES_DBG_INIT,

This indentation is hard to read, because the then clause visually runs
into the condition being tested.  I generally align the follow-on lines
to be just inside the opening ( of "if (".  And there's no reason to put
parentheses around limit_maxrdreqsz...

 > +		pci_read_config_word(pcidev, 0x68, &maxrdreqword);
 > +		/* set bits 12-14 to 001b = 256 bytes */
 > +		maxrdreqword &= 0x8fff;
 > +		maxrdreqword |= 0x1000;
 > +		pci_write_config_word(pcidev, 0x68, maxrdreqword);

I would write this as below, using the standard pcie interfaces and also
being defensive so as not to set the max read req to 256 if the
BIOS/kernel had limited it to 128 already:

	if (pcie_get_readrq(pcidev) > 256)
		if (pcie_set_readrq(pcidev, 256)) {
			/* report error */
		}

 - R.