Re: [PATCH v2] ath10k: Replace ioread with mb to drain write buffer

[Peter Oh <poh@qca.qualcomm.com>]

On 01/30/2015 04:14 PM, Peter Oh wrote:
> Using ioread() to perform draining write buffer is excessive.
> Use compact API, mb(), that intended to be used for the case.
> It reduces total 14 CPU clocks per interrupt.
>
> Signed-off-by: Peter Oh <poh@qca.qualcomm.com>
> ---
>   drivers/net/wireless/ath/ath10k/pci.c | 12 ++++--------
>   1 file changed, 4 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/net/wireless/ath/ath10k/pci.c b/drivers/net/wireless/ath/ath10k/pci.c
> index e6972b0..f1e6980 100644
> --- a/drivers/net/wireless/ath/ath10k/pci.c
> +++ b/drivers/net/wireless/ath/ath10k/pci.c
> @@ -353,10 +353,8 @@ static void ath10k_pci_disable_and_clear_legacy_irq(struct ath10k *ar)
>   	ath10k_pci_write32(ar, SOC_CORE_BASE_ADDRESS + PCIE_INTR_CLR_ADDRESS,
>   			   PCIE_INTR_FIRMWARE_MASK | PCIE_INTR_CE_MASK_ALL);
>   
> -	/* IMPORTANT: this extra read transaction is required to
> -	 * flush the posted write buffer. */
> -	(void)ath10k_pci_read32(ar, SOC_CORE_BASE_ADDRESS +
> -				PCIE_INTR_ENABLE_ADDRESS);
> +	/* drain write buffer */
> +	mb();
It figured out that ath10k_pci_read32() use dsb with 'st' while wmb() is 
use with 'sy'.
So updated it from wmb() to mb() for the same effect as ath10k_pci_read32().
>   }
>   
>   static void ath10k_pci_enable_legacy_irq(struct ath10k *ar)
> @@ -365,10 +363,8 @@ static void ath10k_pci_enable_legacy_irq(struct ath10k *ar)
>   			   PCIE_INTR_ENABLE_ADDRESS,
>   			   PCIE_INTR_FIRMWARE_MASK | PCIE_INTR_CE_MASK_ALL);
>   
> -	/* IMPORTANT: this extra read transaction is required to
> -	 * flush the posted write buffer. */
> -	(void)ath10k_pci_read32(ar, SOC_CORE_BASE_ADDRESS +
> -				PCIE_INTR_ENABLE_ADDRESS);
> +	/* drain write buffer */
> +	mb();
>   }
>   
>   static inline const char *ath10k_pci_get_irq_method(struct ath10k *ar)
Thanks,
Peter

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