From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Simek Subject: Re: [PATCH 1/2] can: xilinx: use readl/writel instead of ioread/iowrite Date: Thu, 22 Oct 2015 11:49:53 +0200 Message-ID: <5628B141.1010307@xilinx.com> References: <1445489163-11045-1-git-send-email-appanad@xilinx.com> <4061693.oBld7AKBIp@wuerfel> <3847286.pUBWjpC1TL@wuerfel> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Appana Durga Kedareswara Rao , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-can@vger.kernel.org" , "mkl@pengutronix.de" , Soren Brinkmann , Anirudha Sarangi , "wg@grandegger.com" To: Arnd Bergmann , Return-path: In-Reply-To: <3847286.pUBWjpC1TL@wuerfel> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org List-Id: netdev.vger.kernel.org On 10/22/2015 11:02 AM, Arnd Bergmann wrote: > On Thursday 22 October 2015 08:34:53 Appana Durga Kedareswara Rao wrote: >>> On Thursday 22 October 2015 10:16:02 Kedareswara rao Appana wrote: >>>> The driver only supports memory-mapped I/O [by ioremap()], so >>>> readl/writel is actually the right thing to do, IMO. >>>> During the validation of this driver or IP on ARM 64-bit processor >>>> while sending lot of packets observed that the tx packet drop with >>>> iowrite Putting the barriers for each tx fifo register write fixes >>>> this issue Instead of barriers using writel also fixed this issue. >>>> >>>> Signed-off-by: Kedareswara rao Appana >>> >>> The two should really do the same thing: iowrite32() is just a static inline calling >>> writel() on both ARM32 and ARM64. On which kernel version did you observe the >>> difference? It's possible that an older version used CONFIG_GENERIC_IOMAP, >>> which made this slightly more expensive. >> >> I observed this issue with the 4.0.0 kernel version > > Is it possible that you have nonstandard patches on your kernel? If so, can > you send a diff against the mainline version? Kedar: Can you please retest this on mainline kernel? We shouldn't have any patches which should influence this. Thanks, Michal