From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Newton Subject: [PATCH v2] omap_hsmmc: Reduce max_segs for reliability Date: Thu, 22 Jun 2017 11:57:53 +0100 Message-ID: <20170622105753.28708-1-willn@resin.io> Return-path: Received: from mail-wr0-f194.google.com ([209.85.128.194]:36273 "EHLO mail-wr0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752743AbdFVK6N (ORCPT ); Thu, 22 Jun 2017 06:58:13 -0400 Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: linux-omap@vger.kernel.org Cc: linux-mmc@vger.kernel.org, tony@atomide.com, kishon@ti.com, rk@ti.com, Will Newton Reduce max_segs to 64, a value that allows allocation of an entire EDMA descriptor list within a single page - EDMA descriptors are 40 bytes and the header is much larger. This avoids doing a higher order GFP_ATOMIC allocation in edma_prep_slave_sg when setting up a transfer which can potentially fail due to fragmentation under heavy I/O load. The current value of 1024 is unusually high in comparison to other mmc host drivers which mostly use values of between 1 and 256. The EDMA driver at present splits lists above 20 segments in any case so reducing the size of lists we pass to it shouldn't add much overhead. Signed-off-by: Will Newton --- drivers/mmc/host/omap_hsmmc.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) Changes in v2: - More verbose commit message - Rebased onto current master diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c index 8c39dcc..bbcca93 100644 --- a/drivers/mmc/host/omap_hsmmc.c +++ b/drivers/mmc/host/omap_hsmmc.c @@ -2097,9 +2097,9 @@ static int omap_hsmmc_probe(struct platform_device *pdev) host->dbclk = NULL; } - /* Since we do only SG emulation, we can have as many segs - * as we want. */ - mmc->max_segs = 1024; + /* Set this to a value that allows allocating an entire descriptor + * list within a page (zero order allocation). */ + mmc->max_segs = 64; mmc->max_blk_size = 512; /* Block Length at max can be 1024 */ mmc->max_blk_count = 0xFFFF; /* No. of Blocks is 16 bits */ -- 2.9.4