From mboxrd@z Thu Jan 1 00:00:00 1970 From: jorge.ramirez-ortiz@linaro.org (Jorge Ramirez-Ortiz) Date: Mon, 23 Feb 2015 15:16:39 -0500 Subject: [PATCH] drivers/tty: amba-pl011: defer driver probing if external dma is not ready. Message-ID: <1424722599-9215-1-git-send-email-jorge.ramirez-ortiz@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org This patch addresses 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 proposed implementation uses deferred driver probing to wait for the DMA controller to be registered. Signed-off-by: Jorge Ramirez-Ortiz --- drivers/tty/serial/amba-pl011.c | 70 +++++++++++------------------------------ 1 file changed, 18 insertions(+), 52 deletions(-) diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c index 8d94c19..40219e5 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 @@ -261,7 +262,7 @@ 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 int 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); @@ -275,13 +276,17 @@ 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"); + chan = dma_request_slave_channel_reason(dev, "tx"); + if (IS_ERR(chan)) { + + /* the dma driver has not been initialized yet */ + if (PTR_ERR(chan) == -EPROBE_DEFER) + return -EPROBE_DEFER; - if (!chan) { /* We need platform data */ if (!plat || !plat->dma_filter) { dev_info(uap->port.dev, "no DMA platform data\n"); - return; + return 0; } /* Try to acquire a generic DMA engine slave TX channel */ @@ -292,7 +297,7 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port * plat->dma_tx_param); if (!chan) { dev_err(uap->port.dev, "no TX DMA channel!\n"); - return; + return 0; } } @@ -310,7 +315,7 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port * if (!chan) { dev_err(uap->port.dev, "no RX DMA channel!\n"); - return; + return 0; } } @@ -383,54 +388,10 @@ 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); - } -} -#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 */ @@ -1142,8 +1103,9 @@ static inline bool pl011_dma_rx_running(struct uart_amba_port *uap) #else /* Blank functions if the DMA engine is not available */ -static inline void pl011_dma_probe(struct device *dev, struct uart_amba_port *uap) +static int pl011_dma_probe(struct device *dev, struct uart_amba_port *uap) { + return 0; } static inline void pl011_dma_remove(struct uart_amba_port *uap) @@ -2218,7 +2180,11 @@ 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); + ret = pl011_dma_probe(&dev->dev, uap); + if (ret) { + devm_kfree(&dev->dev, uap); + return ret; + } /* Ensure interrupts from this UART are masked and cleared */ writew(0, uap->port.membase + UART011_IMSC); -- 1.9.1