From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Hutchings Subject: [PATCH net-2.6 3/3] sfc: Use rmb() to ensure reads occur in order Date: Wed, 13 Apr 2011 00:50:34 +0100 Message-ID: <1302652234.2880.31.camel@bwh-desktop> References: <1302652065.2880.28.camel@bwh-desktop> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, linux-net-drivers@solarflare.com To: David Miller Return-path: Received: from mail.solarflare.com ([216.237.3.220]:12641 "EHLO exchange.solarflare.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932095Ab1DLXuh (ORCPT ); Tue, 12 Apr 2011 19:50:37 -0400 In-Reply-To: <1302652065.2880.28.camel@bwh-desktop> Sender: netdev-owner@vger.kernel.org List-ID: From: Neil Turton Enabling write-combining may also enable read reordering. The BIU is only guaranteed to read from a 128-bit CSR or 64-bit SRAM word when the host reads from its lowest address; otherwise the BIU may use the latched value. Therefore we need to reinstate the read memory barriers after the first read operation for each CSR or SRAM word. Signed-off-by; Ben Hutchings --- drivers/net/sfc/io.h | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-) diff --git a/drivers/net/sfc/io.h b/drivers/net/sfc/io.h index d9d8c2e..cc97880 100644 --- a/drivers/net/sfc/io.h +++ b/drivers/net/sfc/io.h @@ -152,6 +152,7 @@ static inline void efx_reado(struct efx_nic *efx, efx_oword_t *value, spin_lock_irqsave(&efx->biu_lock, flags); value->u32[0] = _efx_readd(efx, reg + 0); + rmb(); value->u32[1] = _efx_readd(efx, reg + 4); value->u32[2] = _efx_readd(efx, reg + 8); value->u32[3] = _efx_readd(efx, reg + 12); @@ -174,6 +175,7 @@ static inline void efx_sram_readq(struct efx_nic *efx, void __iomem *membase, value->u64[0] = (__force __le64)__raw_readq(membase + addr); #else value->u32[0] = (__force __le32)__raw_readl(membase + addr); + rmb(); value->u32[1] = (__force __le32)__raw_readl(membase + addr + 4); #endif spin_unlock_irqrestore(&efx->biu_lock, flags); -- 1.7.4 -- Ben Hutchings, Senior Software Engineer, Solarflare Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked.