From mboxrd@z Thu Jan 1 00:00:00 1970 From: jorge.ramirez-ortiz@linaro.org (Jorge Ramirez-Ortiz) Date: Mon, 23 Feb 2015 22:33:46 -0500 Subject: [PATCH] drivers/tty: amba-pl011: defer driver probing if external dma is not ready. In-Reply-To: References: <1424722599-9215-1-git-send-email-jorge.ramirez-ortiz@linaro.org> Message-ID: <54EBF11A.1030806@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 02/23/2015 03:58 PM, Rob Herring wrote: > +spear maintainers > > On Mon, Feb 23, 2015 at 2:16 PM, Jorge Ramirez-Ortiz > wrote: >> 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. > This is going to break implementations using platform data rather than > DT for the DMA channel resolving. The only user is spear3xx. Ideally, > we should fix spear3xx to use DT for the DMA channels. That would > mainly require making the pl08x driver DT enabled and dts updates. > > To fix this in the pl011 driver, you are going to need to split up the > DT and platform data paths keeping the list used for the platform > data. The platform data is only used for DMA and is mutually exclusive > with DT, so in probe you can do something like this: > > if (pdata) > pdata_dma_probe(); > else if (of_dma_probe() == -EPROBE_DEFER) > return -EPROBE_DEFER; thanks Rob. Ok fix on its way. sorry about this. > > Rob > >> 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 >>