From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robert Hancock Subject: Re: [RFC PATCH] AHCI: Workaround for ATAPI on buggy AHCI controller Date: Fri, 12 Apr 2013 23:05:17 -0600 Message-ID: <5168E78D.90805@gmail.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-ia0-f178.google.com ([209.85.210.178]:44650 "EHLO mail-ia0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751940Ab3DMFFU (ORCPT ); Sat, 13 Apr 2013 01:05:20 -0400 Received: by mail-ia0-f178.google.com with SMTP id w21so1175563iac.23 for ; Fri, 12 Apr 2013 22:05:19 -0700 (PDT) In-Reply-To: Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Marc C Cc: jeff@garzik.org, linux-ide@vger.kernel.org On 04/12/2013 01:34 PM, Marc C wrote: > Hello Jeff, > > I'm working with a proprietary but AHCI-compatible SATA controller that uses > the libata driver. Early versions of this controller have issues with processing > non-data ATAPI commands. A workaround was identified which requires some > register pokes in the command completion path of the driver. I don't expect to > push this patch upstream (yet). However, I would like to get some feedback > regarding the workaround, and check if the placement of the code is "acceptable" > or if there would be a better place to put it. > > The workaround itself is rather simple: toggle the START bit immediately after a > non-data ATAPI command completes. The ST bit toggle would be performed within > atomic context in the AHCI port interrupt ISR. > > Signed-off-by: Marc C This should likely be triggered off a host flag like some of the ones already in the driver so it can be done just for the affected controllers, not unconditionally. > --- > linux/drivers/ata/libahci.c | 26 ++++++++++++++++++++++++++ > linux/drivers/ata/libata-core.c | 6 ++++++ > 2 files changed, 32 insertions(+) > > diff --git a/linux/drivers/ata/libahci.c b/linux/drivers/ata/libahci.c > index f9eaa82..20b3a9a 100644 > --- a/linux/drivers/ata/libahci.c > +++ b/linux/drivers/ata/libahci.c > @@ -2215,6 +2215,32 @@ void ahci_set_em_messages(struct ahci_host_priv *hpriv, > } > EXPORT_SYMBOL_GPL(ahci_set_em_messages); > > +void ahci_apply_atapi_workaround(struct ata_queued_cmd *qc) > +{ > + if (!(qc->flags & ATA_QCFLAG_DMAMAP)) { > + /* > + * Non-data ATAPI commands need to kick the DMA engine > + */ > + struct ata_port *ap = qc->ap; > + void __iomem *port_mmio = ahci_port_base(ap); > + u32 tmp = readl(port_mmio + PORT_CMD); > + > + /* check if the HBA is idle */ > + if ((tmp & (PORT_CMD_START | PORT_CMD_LIST_ON)) != 0) { > + /* setting HBA to idle */ > + tmp &= ~PORT_CMD_START; > + writel(tmp, port_mmio + PORT_CMD); > + > + /* wait for engine to stop */ > + do { > + tmp = readl(port_mmio + PORT_CMD); > + } while (tmp & PORT_CMD_LIST_ON); > + } > + ahci_start_engine(ap); > + } > +} > +EXPORT_SYMBOL_GPL(ahci_apply_atapi_workaround); > + > MODULE_AUTHOR("Jeff Garzik"); > MODULE_DESCRIPTION("Common AHCI SATA low-level routines"); > MODULE_LICENSE("GPL"); > diff --git a/linux/drivers/ata/libata-core.c b/linux/drivers/ata/libata-core.c > index 4e73e1b..383de21 100644 > --- a/linux/drivers/ata/libata-core.c > +++ b/linux/drivers/ata/libata-core.c > @@ -4827,6 +4827,12 @@ void ata_qc_complete(struct ata_queued_cmd *qc) > { > struct ata_port *ap = qc->ap; > > + if (ata_is_atapi(qc->tf.protocol)) { > + void ahci_apply_atapi_workaround(struct ata_queued_cmd *qc); > + ahci_apply_atapi_workaround(qc); > + } > + > /* XXX: New EH and old EH use different mechanisms to > * synchronize EH with regular execution path. > * > -- > 1.7.9.5 > > > > > -- > Regards, > Marc > marc.ceeeee@gmail.com > -- > 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 >