| Message ID | 1268253150-24050-1-git-send-email-mjg@redhat.com |
|---|---|
| State | Not Applicable |
| Delegated to: | David Miller |
| Headers | show |
Any feedback on this? On Wed, Mar 10, 2010 at 03:32:30PM -0500, Matthew Garrett wrote: > According to section 10.3.1 of the AHCI spec, PxCMD.ST must not be set > unless there's a device attached. Following this saves us a measurable > quantity of power and does not impair hotplug support. Based on a patch > by Kristen Carlson Accardi. > > Signed-off-by: Matthew Garrett <mjg@redhat.com> > Cc: Kristen Carlson Accardi <kristen.c.accardi@intel.com> > --- > drivers/ata/ahci.c | 19 +++++++++++++++++++ > 1 files changed, 19 insertions(+), 0 deletions(-) > > diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c > index 6bd930b..ff08317 100644 > --- a/drivers/ata/ahci.c > +++ b/drivers/ata/ahci.c > @@ -1016,11 +1016,30 @@ static int ahci_scr_write(struct ata_link *link, unsigned int sc_reg, u32 val) > return -EINVAL; > } > > +static int ahci_is_device_present(struct ata_port *ap) > +{ > + void __iomem *port_mmio = ahci_port_base(ap); > + u8 status = readl(port_mmio + PORT_TFDATA) & 0xff; > + > + /* Make sure PxTFD.STS.BSY and PxTFD.STS.DRQ are 0 */ > + if (status & (ATA_BUSY | ATA_DRQ)) > + return 0; > + > + /* Make sure PxSSTS.DET is 3h */ > + status = readl(port_mmio + PORT_SCR_STAT) & 0xf; > + if (status != 3) > + return 0; > + return 1; > +} > + > static void ahci_start_engine(struct ata_port *ap) > { > void __iomem *port_mmio = ahci_port_base(ap); > u32 tmp; > > + if (!ahci_is_device_present(ap)) > + return; > + > /* start DMA */ > tmp = readl(port_mmio + PORT_CMD); > tmp |= PORT_CMD_START; > -- > 1.6.6.1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-ide" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >
On 03/24/2010 10:19 AM, Matthew Garrett wrote: > On Wed, Mar 10, 2010 at 03:32:30PM -0500, Matthew Garrett wrote: >> According to section 10.3.1 of the AHCI spec, PxCMD.ST must not be set >> unless there's a device attached. Following this saves us a measurable >> quantity of power and does not impair hotplug support. Based on a patch >> by Kristen Carlson Accardi. >> >> Signed-off-by: Matthew Garrett<mjg@redhat.com> >> Cc: Kristen Carlson Accardi<kristen.c.accardi@intel.com> >> --- >> drivers/ata/ahci.c | 19 +++++++++++++++++++ >> 1 files changed, 19 insertions(+), 0 deletions(-) (please don't top-post, it makes replying more difficult) > Any feedback on this? It should be fine, but I have to rebase it onto the latest upstream ahci (libata-dev.git#upstream), so it's been waiting on that... Jeff -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 03/10/2010 03:32 PM, Matthew Garrett wrote: > According to section 10.3.1 of the AHCI spec, PxCMD.ST must not be set > unless there's a device attached. Following this saves us a measurable > quantity of power and does not impair hotplug support. Based on a patch > by Kristen Carlson Accardi. > > Signed-off-by: Matthew Garrett<mjg@redhat.com> > Cc: Kristen Carlson Accardi<kristen.c.accardi@intel.com> > --- > drivers/ata/ahci.c | 19 +++++++++++++++++++ > 1 files changed, 19 insertions(+), 0 deletions(-) applied manually to libata-dev.git#upstream, due to large code movements in creation of new libahci kernel module -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 03/10/2010 03:32 PM, Matthew Garrett wrote: > +static int ahci_is_device_present(struct ata_port *ap) > +{ > + void __iomem *port_mmio = ahci_port_base(ap); > + u8 status = readl(port_mmio + PORT_TFDATA)& 0xff; > + > + /* Make sure PxTFD.STS.BSY and PxTFD.STS.DRQ are 0 */ > + if (status& (ATA_BUSY | ATA_DRQ)) > + return 0; > + > + /* Make sure PxSSTS.DET is 3h */ > + status = readl(port_mmio + PORT_SCR_STAT)& 0xf; > + if (status != 3) > + return 0; > + return 1; Note that this last test, reading SATA Control Register (SCR) Status, does not account for in-transition status, ie. devices that were just plugged in. Jeff -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c index 6bd930b..ff08317 100644 --- a/drivers/ata/ahci.c +++ b/drivers/ata/ahci.c @@ -1016,11 +1016,30 @@ static int ahci_scr_write(struct ata_link *link, unsigned int sc_reg, u32 val) return -EINVAL; } +static int ahci_is_device_present(struct ata_port *ap) +{ + void __iomem *port_mmio = ahci_port_base(ap); + u8 status = readl(port_mmio + PORT_TFDATA) & 0xff; + + /* Make sure PxTFD.STS.BSY and PxTFD.STS.DRQ are 0 */ + if (status & (ATA_BUSY | ATA_DRQ)) + return 0; + + /* Make sure PxSSTS.DET is 3h */ + status = readl(port_mmio + PORT_SCR_STAT) & 0xf; + if (status != 3) + return 0; + return 1; +} + static void ahci_start_engine(struct ata_port *ap) { void __iomem *port_mmio = ahci_port_base(ap); u32 tmp; + if (!ahci_is_device_present(ap)) + return; + /* start DMA */ tmp = readl(port_mmio + PORT_CMD); tmp |= PORT_CMD_START;
According to section 10.3.1 of the AHCI spec, PxCMD.ST must not be set unless there's a device attached. Following this saves us a measurable quantity of power and does not impair hotplug support. Based on a patch by Kristen Carlson Accardi. Signed-off-by: Matthew Garrett <mjg@redhat.com> Cc: Kristen Carlson Accardi <kristen.c.accardi@intel.com> --- drivers/ata/ahci.c | 19 +++++++++++++++++++ 1 files changed, 19 insertions(+), 0 deletions(-)