Hello,
On Mon, Jun 23, 2014 at 03:23:13PM +0530, Suman Tripathi wrote:
> This patch fixes the dma state machine lockup due to the processing
> of IDENTIFY DEVICE PIO mode command. The X-Gene AHCI controller
> has an errata in which it cannot clear the BSY bit after
> receiving the PIO setup FIS and results the dma state machine to go
> into the CMFatalErrorUpdate state resulting in the dma state
> machine lockup. This patch also removes the dma restart workaround
> from the read_id function as the read_id function is only called by
> libata layer for ATA_INTERNAL commands. But for somecases eg:
> PORT MULTIPLIER and udev, the framework will enumerate using SCSI
> commands and it will not call read_id function.
I assume that it's verified that only IDENTIFY is affected? Please
try to explicitly follow up on the previous discussions. It makes
keeping track a lot easier for the reviewers.
> /**
> + * xgene_ahci_qc_issue - Issue commands to the device
> + * @qc: Command to issue
> + *
> + * Due to H/W errata, for the IDENTIFY DEVICE command controller is unable to
> + * clear the BSY bit after receiving the PIO setup FIS and results the dma
> + * state machine to go into the CMFatalErrorUpdate state resulting in the dma
> + * state machine lockup. By restarting the dma engine to move it removes the
> + * controller out of lock up state.
> + */
> +static unsigned int xgene_ahci_qc_issue(struct ata_queued_cmd *qc)
> +{
> + struct ata_port *ap = qc->ap;
> + struct ahci_host_priv *hpriv = ap->host->private_data;
> + struct xgene_ahci_context *ctx = hpriv->plat_data;
> + int rc = 0;
> +
> + /*
> + * Restart the dma engine if the last cmd issued
> + * is IDENTIFY DEVICE command
> + */
I think the function comment is doing a good job of explaining and we
can lose the above comment. Comments which explain the code itself is
useful if the logic involved is complex but I don't think that's the
case here.
> + if (unlikely(ctx->last_cmd[ap->port_no] == ATA_CMD_ID_ATA))
> + ahci_restart_engine(ap);
> +
> + rc = ahci_qc_issue(qc);
> +
> + /* Save the last command issued */
> + ctx->last_cmd[ap->port_no] = qc->tf.command;
> +
> + return rc;
> +}
...
> diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
> index d1c9122..1b86cf4 100644
> --- a/drivers/ata/libahci.c
> +++ b/drivers/ata/libahci.c
> @@ -68,7 +68,6 @@ static ssize_t ahci_transmit_led_message(struct ata_port *ap, u32 state,
>
> static int ahci_scr_read(struct ata_link *link, unsigned int sc_reg, u32 *val);
> static int ahci_scr_write(struct ata_link *link, unsigned int sc_reg, u32 val);
> -static unsigned int ahci_qc_issue(struct ata_queued_cmd *qc);
> static bool ahci_qc_fill_rtf(struct ata_queued_cmd *qc);
> static int ahci_port_start(struct ata_port *ap);
> static void ahci_port_stop(struct ata_port *ap);
> @@ -1952,7 +1951,7 @@ irqreturn_t ahci_interrupt(int irq, void *dev_instance)
> }
> EXPORT_SYMBOL_GPL(ahci_interrupt);
>
> -static unsigned int ahci_qc_issue(struct ata_queued_cmd *qc)
> +unsigned int ahci_qc_issue(struct ata_queued_cmd *qc)
> {
> struct ata_port *ap = qc->ap;
> void __iomem *port_mmio = ahci_port_base(ap);
> @@ -1981,6 +1980,7 @@ static unsigned int ahci_qc_issue(struct ata_queued_cmd *qc)
>
> return 0;
> }
> +EXPORT_SYMBOL_GPL(ahci_qc_issue);
Can we please do this in the previous patch? "implement
ahci_restart_engine() and export ahci_qc_issue()" is completely fine
with me. Just note in the description that a following patch will
make use of them.
Thanks.
--
tejun
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