linux-kernel - Re: [PATCH V3] AHCI: Workaround for ThunderX Errata#22536

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Date:	Tue, 23 Feb 2016 16:00:31 -0800
From:	Tirumalesh Chalamarla <tchalamarla@...iumnetworks.com>
To:	<tj@...nel.org>
CC:	<stripathi@....com>, <linux-ide@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH V3] AHCI: Workaround for ThunderX Errata#22536

Hi Tejun,

Any more comments on this?

Thanks,
Tirumalesh.


On 02/16/2016 12:08 PM, tchalamarla@...iumnetworks.com wrote:
> From: Tirumalesh Chalamarla <tchalamarla@...iumnetworks.com>
>
> Due to Errata in ThunderX, HOST_IRQ_STAT should be
> cleared before leaving the interrupt handler.
> The patch attempts to satisfy the need.
>
> Changes from V2:
> 	- removed newfile
> 	- code is now under CONFIG_ARM64
>
> Changes from V1:
> 	- Rebased on top of libata/for-4.6
>          - Moved ThunderX intr handler to new file
>
> Signed-off-by: Tirumalesh Chalamarla <tchalamarla@...iumnetworks.com>
> ---
>   drivers/ata/ahci.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 44 insertions(+)
>
> diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
> index 546a369..c8496fc 100644
> --- a/drivers/ata/ahci.c
> +++ b/drivers/ata/ahci.c
> @@ -1325,6 +1325,44 @@ static inline void ahci_gtf_filter_workaround(struct ata_host *host)
>   {}
>   #endif
>
> +#ifdef CONFIG_ARM64
> +/* Due to ERRATA#22536, ThunderX need to handle
> + * HOST_IRQ_STAT differently.
> + * Work around is to make sure all pending IRQs
> + * are served before leaving handler
> + */
> +static irqreturn_t ahci_thunderx_irq_handler(int irq, void *dev_instance)
> +{
> +	struct ata_host *host = dev_instance;
> +	struct ahci_host_priv *hpriv;
> +	unsigned int rc = 0;
> +	void __iomem *mmio;
> +	u32 irq_stat, irq_masked;
> +	unsigned int handled = 1;
> +
> +	VPRINTK("ENTER\n");
> +	hpriv = host->private_data;
> +	mmio = hpriv->mmio;
> +	irq_stat = readl(mmio + HOST_IRQ_STAT);
> +	if (!irq_stat)
> +		return IRQ_NONE;
> +
> +	do {
> +		irq_masked = irq_stat & hpriv->port_map;
> +		spin_lock(&host->lock);
> +		rc = ahci_handle_port_intr(host, irq_masked);
> +		if (!rc)
> +			handled = 0;
> +		writel(irq_stat, mmio + HOST_IRQ_STAT);
> +		irq_stat = readl(mmio + HOST_IRQ_STAT);
> +		spin_unlock(&host->lock);
> +	} while (irq_stat);
> +	VPRINTK("EXIT\n");
> +
> +	return IRQ_RETVAL(handled);
> +}
> +#endif
> +
>   /*
>    * ahci_init_msix() - optionally enable per-port MSI-X otherwise defer
>    * to single msi.
> @@ -1560,6 +1598,12 @@ static int ahci_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
>   	if (ahci_broken_devslp(pdev))
>   		hpriv->flags |= AHCI_HFLAG_NO_DEVSLP;
>
> +#ifdef CONFIG_ARM64
> +	/* this should be done before save config*/
> +	if (pdev->vendor == 0x177d && pdev->device == 0xa01c)
> +		hpriv->irq_handler = ahci_thunderx_irq_handler;
> +#endif
> +
>   	/* save initial config */
>   	ahci_pci_save_initial_config(pdev, hpriv);
>
>