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[67.247.86.207]) by mx.google.com with ESMTPSA id e23sm19371215qhc.21.2015.02.25.16.31.12 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 25 Feb 2015 16:31:13 -0800 (PST) From: Jorge Ramirez-Ortiz To: jorge.ramirez-ortiz@linaro.org, arnd@arndb.de, linux-arm-kernel@lists.infradead.org, robh@kernel.org, viresh.kumar@linaro.org Subject: [PATCH v3] drivers/tty: amba: defer probing DMA availability until hw_init Date: Wed, 25 Feb 2015 19:31:01 -0500 Message-Id: <1424910661-26474-1-git-send-email-jorge.ramirez-ortiz@linaro.org> X-Mailer: git-send-email 1.9.1 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20150225_163921_179623_2B15B83E X-CRM114-Status: GOOD ( 18.61 ) X-Spam-Score: -0.7 (/) X-Spam-Report: SpamAssassin version 3.4.0 on bombadil.infradead.org summary: Content analysis details: (-0.7 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.7 RCVD_IN_DNSWL_LOW RBL: Sender listed at http://www.dnswl.org/, low trust [209.85.216.182 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record -0.0 RCVD_IN_MSPIKE_H3 RBL: Good reputation (+3) [209.85.216.182 listed in wl.mailspike.net] -0.0 RCVD_IN_MSPIKE_WL Mailspike good senders X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: , List-Help: , List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patch=linaro.org@lists.infradead.org X-Removed-Original-Auth: Dkim didn't pass. X-Original-Sender: jorge.ramirez-ortiz@linaro.org X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of patch+caf_=patchwork-forward=linaro.org@linaro.org designates 209.85.217.182 as permitted sender) smtp.mail=patch+caf_=patchwork-forward=linaro.org@linaro.org Mailing-list: list patchwork-forward@linaro.org; contact patchwork-forward+owners@linaro.org X-Google-Group-Id: 836684582541 Fix a race condition that happens when device_initcall(pl011_dma_initicall) is executed before all the devices have been probed - this issue was observed on an hisi_6220 SoC (HiKey board from Linaro). The deferred driver probing framework relies on late_initcall to trigger deferred probes so it is just possible that, even with a valid DMA driver ready to be loaded, we fail to synchronize with it. The proposed implementation delays probing of the DMA until the uart device is opened. As hw_init is invoked on port startup and port resume - but the DMA probe is only required once - we avoid calling multiple times using a new field in uart_amba_port to track this scenario. Signed-off-by: Jorge Ramirez-Ortiz --- drivers/tty/serial/amba-pl011.c | 66 ++++++++++------------------------------- 1 file changed, 16 insertions(+), 50 deletions(-) diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c index 8d94c19..3501ccc 100644 --- a/drivers/tty/serial/amba-pl011.c +++ b/drivers/tty/serial/amba-pl011.c @@ -29,6 +29,7 @@ * and hooked into this driver. */ +#define pr_fmt(fmt) "amba-pl011: "fmt #if defined(CONFIG_SERIAL_AMBA_PL011_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ) #define SUPPORT_SYSRQ @@ -164,6 +165,7 @@ struct uart_amba_port { bool using_rx_dma; struct pl011_dmarx_data dmarx; struct pl011_dmatx_data dmatx; + bool dma_probed; #endif }; @@ -261,7 +263,7 @@ static void pl011_sgbuf_free(struct dma_chan *chan, struct pl011_sgbuf *sg, } } -static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port *uap) +static void pl011_dma_probe(struct device *dev, struct uart_amba_port *uap) { /* DMA is the sole user of the platform data right now */ struct amba_pl011_data *plat = dev_get_platdata(uap->port.dev); @@ -275,9 +277,16 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port * struct dma_chan *chan; dma_cap_mask_t mask; - chan = dma_request_slave_channel(dev, "tx"); + uap->dma_probed = true; + + chan = dma_request_slave_channel_reason(dev, "tx"); + if (IS_ERR(chan)) { + if (PTR_ERR(chan) == -EPROBE_DEFER) { + dev_warn(uap->port.dev, "DMA driver not ready\n"); + return; + } + dev_info(uap->port.dev, "no OF or ACPI DMA data\n"); - if (!chan) { /* We need platform data */ if (!plat || !plat->dma_filter) { dev_info(uap->port.dev, "no DMA platform data\n"); @@ -383,54 +392,9 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port * dev_info(uap->port.dev, "DMA channel RX %s\n", dma_chan_name(uap->dmarx.chan)); } -} - -#ifndef MODULE -/* - * Stack up the UARTs and let the above initcall be done at device - * initcall time, because the serial driver is called as an arch - * initcall, and at this time the DMA subsystem is not yet registered. - * At this point the driver will switch over to using DMA where desired. - */ -struct dma_uap { - struct list_head node; - struct uart_amba_port *uap; - struct device *dev; -}; - -static LIST_HEAD(pl011_dma_uarts); - -static int __init pl011_dma_initcall(void) -{ - struct list_head *node, *tmp; - - list_for_each_safe(node, tmp, &pl011_dma_uarts) { - struct dma_uap *dmau = list_entry(node, struct dma_uap, node); - pl011_dma_probe_initcall(dmau->dev, dmau->uap); - list_del(node); - kfree(dmau); - } - return 0; -} - -device_initcall(pl011_dma_initcall); -static void pl011_dma_probe(struct device *dev, struct uart_amba_port *uap) -{ - struct dma_uap *dmau = kzalloc(sizeof(struct dma_uap), GFP_KERNEL); - if (dmau) { - dmau->uap = uap; - dmau->dev = dev; - list_add_tail(&dmau->node, &pl011_dma_uarts); - } + return; } -#else -static void pl011_dma_probe(struct device *dev, struct uart_amba_port *uap) -{ - pl011_dma_probe_initcall(dev, uap); -} -#endif - static void pl011_dma_remove(struct uart_amba_port *uap) { /* TODO: remove the initcall if it has not yet executed */ @@ -1548,6 +1512,9 @@ static int pl011_hwinit(struct uart_port *port) uap->im = readw(uap->port.membase + UART011_IMSC); writew(UART011_RTIM | UART011_RXIM, uap->port.membase + UART011_IMSC); + if (!uap->dma_probed) + pl011_dma_probe(uap->port.dev, uap); + if (dev_get_platdata(uap->port.dev)) { struct amba_pl011_data *plat; @@ -2218,7 +2185,6 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id) uap->port.ops = &amba_pl011_pops; uap->port.flags = UPF_BOOT_AUTOCONF; uap->port.line = i; - pl011_dma_probe(&dev->dev, uap); /* Ensure interrupts from this UART are masked and cleared */ writew(0, uap->port.membase + UART011_IMSC);