The zpci_get_max_write_size() helper is used to determine the maximum size a PCI store or load can use at a given __iomem address. For the PCI block store the following restrictions apply: 1. The dst + len must not cross a 4K boundary in the (pseudo-)MMIO space 2. len must not exceed ZPCI_MAX_WRITE_SIZE 3. len must be a multiple of 8 bytes 4. The src address must be double word (8 byte) aligned 5. The dst address must be double word (8 byte) aligned Otherwise only a normal PCI store which takes its src value from a register can be used. For these PCI store restriction 1 still applies. Similarly 1 also applies to PCI loads. It turns out zpci_max_write_size() instead implements stricter conditions which prevents PCI block stores from being used where they can and should be used. In particular instead of conditions 4 and 5 it wrongly enforces both dst and src to be size aligned. This indirectly covers condition 1 but also prevents many legal PCI block stores. On top of the functional shortcomings the zpci_get_max_write_size() is misnamed as it is used for both read and write size calculations. Rename it to zpci_get_max_io_size() and implement the listed conditions explicitly. Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com> Fixes: cd24834130ac ("s390/pci: base support") Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com> [agordeev@linux.ibm.com replaced spaces with tabs] Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>