From mboxrd@z Thu Jan 1 00:00:00 1970 From: Giuseppe CAVALLARO Subject: Re: [PATCH (net-next.git) 02/18] stmmac: rework DMA bus setting and introduce new platform AXI structure Date: Tue, 5 Jan 2016 10:32:08 +0100 Message-ID: <568B8D98.2020102@st.com> References: <1451912823-5245-1-git-send-email-peppe.cavallaro@st.com> <1451912823-5245-3-git-send-email-peppe.cavallaro@st.com> <20160104.222955.94740482244105696.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Cc: , To: David Miller Return-path: Received: from mx07-00178001.pphosted.com ([62.209.51.94]:64107 "EHLO mx07-00178001.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751530AbcAEJcO (ORCPT ); Tue, 5 Jan 2016 04:32:14 -0500 In-Reply-To: <20160104.222955.94740482244105696.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On 1/5/2016 4:29 AM, David Miller wrote: > From: Giuseppe Cavallaro > Date: Mon, 4 Jan 2016 14:06:47 +0100 > >> @@ -81,7 +81,7 @@ static void stmmac_default_data(struct plat_stmmacenet_data *plat) >> plat->mdio_bus_data->phy_mask = 0; >> >> plat->dma_cfg->pbl = 32; >> - plat->dma_cfg->burst_len = DMA_AXI_BLEN_256; >> + /* TODO: AXI */ >> >> /* Set default value for multicast hash bins */ >> plat->multicast_filter_bins = HASH_TABLE_SIZE; >> @@ -115,8 +115,8 @@ static int quark_default_data(struct plat_stmmacenet_data *plat, >> plat->mdio_bus_data->phy_mask = 0; >> >> plat->dma_cfg->pbl = 16; >> - plat->dma_cfg->burst_len = DMA_AXI_BLEN_256; >> plat->dma_cfg->fixed_burst = 1; >> + /* AXI (TODO) */ >> >> /* Set default value for multicast hash bins */ >> plat->multicast_filter_bins = HASH_TABLE_SIZE; > > Isn't this going to cause a regression for some things? trying to rebuild the story of this setting, I understand it was added to align a configuration so not for fixing some known problem. I do not see any issue on my side indeed with the patch applied. My understanding is that, when we adopt "fixed burst length" it is more safe to use the default burst length instead of tuning it to the maximum value. I met the same on platform driver where for performance issue and just in some cases it helped to play with AXI parameters. For sure, if somebody has different behavior I can shortly arrange the code to keep the previous setting or complete the AXI management for PCI driver (providing a default setup). Let me know what do you think. peppe