sata_sil24: configure max read request size to 4k

Due to request posting limitations, bandwidth of sil3132 is limited to
around 120MB/s with the minimum pci-e payload size (128bytes) which is
used by most consumer systems.  However, write throughput can be
slightly (~3%) increased by increasing the max read requeset size.
Configure it to 4k which is the maximum supported.  This optimization
is also done by SIMG's windows driver.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

diff --git a/drivers/ata/sata_sil24.c b/drivers/ata/sata_sil24.c
index 4621807a1a6a1ffbc143976474141dd529f3fa7f..ccee930f1e1225f8d2918cedd84793ac30b3c007 100644 (file)
--- a/drivers/ata/sata_sil24.c
+++ b/drivers/ata/sata_sil24.c
@@ -1329,6 +1329,11 @@ static int sil24_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
                }
        }
 
+       /* Set max read request size to 4096.  This slightly increases
+        * write throughput for pci-e variants.
+        */
+       pcie_set_readrq(pdev, 4096);
+
        sil24_init_controller(host);
 
        pci_set_master(pdev);