| Message ID | 1424969811-11197-2-git-send-email-jorge.ramirez-ortiz@linaro.org |
|---|---|
| State | New |
| Headers | show |
On 02/26/2015 11:56 AM, Jorge Ramirez-Ortiz wrote: > 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. > > This commit allows for subsequent attempts to associate an external DMA if the > DMA driver was deferred at UART hw_init time. > > Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org> > --- > drivers/tty/serial/amba-pl011.c | 95 +++++++++++++---------------------------- > 1 file changed, 30 insertions(+), 65 deletions(-) > > diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c > index 8d94c19..4ce98e9 100644 > --- a/drivers/tty/serial/amba-pl011.c > +++ b/drivers/tty/serial/amba-pl011.c > @@ -164,6 +164,7 @@ struct uart_amba_port { > bool using_rx_dma; > struct pl011_dmarx_data dmarx; > struct pl011_dmatx_data dmatx; > + bool dma_probed; > #endif > }; > > @@ -261,10 +262,11 @@ 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 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); > + struct device *const uap_dev = uap->port.dev; > + struct amba_pl011_data *plat = dev_get_platdata(uap_dev); > struct dma_slave_config tx_conf = { > .dst_addr = uap->port.mapbase + UART01x_DR, > .dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE, > @@ -275,12 +277,19 @@ 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(uap_dev, "tx"); > + if (IS_ERR(chan)) { > + if (PTR_ERR(chan) == -EPROBE_DEFER) { > + dev_info(uap_dev, "DMA driver not ready\n"); > + uap->dma_probed = false; > + return; > + } > > - if (!chan) { > /* We need platform data */ > if (!plat || !plat->dma_filter) { > - dev_info(uap->port.dev, "no DMA platform data\n"); > + dev_info(uap_dev, "no DMA platform data\n"); > return; > } > > @@ -291,7 +300,7 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port * > chan = dma_request_channel(mask, plat->dma_filter, > plat->dma_tx_param); > if (!chan) { > - dev_err(uap->port.dev, "no TX DMA channel!\n"); > + dev_err(uap_dev, "no TX DMA channel!\n"); > return; > } > } > @@ -299,17 +308,17 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port * > dmaengine_slave_config(chan, &tx_conf); > uap->dmatx.chan = chan; > > - dev_info(uap->port.dev, "DMA channel TX %s\n", > + dev_info(uap_dev, "DMA channel TX %s\n", > dma_chan_name(uap->dmatx.chan)); > > /* Optionally make use of an RX channel as well */ > - chan = dma_request_slave_channel(dev, "rx"); > + chan = dma_request_slave_channel(uap_dev, "rx"); > > if (!chan && plat->dma_rx_param) { > chan = dma_request_channel(mask, plat->dma_filter, plat->dma_rx_param); > > if (!chan) { > - dev_err(uap->port.dev, "no RX DMA channel!\n"); > + dev_err(uap_dev, "no RX DMA channel!\n"); > return; > } > } > @@ -333,7 +342,7 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port * > if (caps.residue_granularity == > DMA_RESIDUE_GRANULARITY_DESCRIPTOR) { > dma_release_channel(chan); > - dev_info(uap->port.dev, > + dev_info(uap_dev, > "RX DMA disabled - no residue processing\n"); > return; > } > @@ -362,75 +371,29 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port * > plat->dma_rx_poll_timeout; > else > uap->dmarx.poll_timeout = 3000; > - } else if (!plat && dev->of_node) { > + } else if (!plat && uap_dev->of_node) { > uap->dmarx.auto_poll_rate = of_property_read_bool( > - dev->of_node, "auto-poll"); > + uap_dev->of_node, "auto-poll"); > if (uap->dmarx.auto_poll_rate) { > u32 x; > > - if (0 == of_property_read_u32(dev->of_node, > + if (0 == of_property_read_u32(uap_dev->of_node, > "poll-rate-ms", &x)) > uap->dmarx.poll_rate = x; > else > uap->dmarx.poll_rate = 100; > - if (0 == of_property_read_u32(dev->of_node, > + if (0 == of_property_read_u32(uap_dev->of_node, > "poll-timeout-ms", &x)) > uap->dmarx.poll_timeout = x; > else > uap->dmarx.poll_timeout = 3000; > } > } > - dev_info(uap->port.dev, "DMA channel RX %s\n", > + dev_info(uap_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 */ > @@ -1142,7 +1105,7 @@ 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 inline void pl011_dma_probe(struct uart_amba_port *uap) > { > } > > @@ -1548,6 +1511,9 @@ 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); > + > if (dev_get_platdata(uap->port.dev)) { > struct amba_pl011_data *plat; > > @@ -2218,7 +2184,6 @@ 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); > @@ -2233,7 +2198,8 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id) > if (!amba_reg.state) { > ret = uart_register_driver(&amba_reg); > if (ret < 0) { > - pr_err("Failed to register AMBA-PL011 driver\n"); > + dev_err(&dev->dev, > + "Failed to register AMBA-PL011 driver\n"); > return ret; > } > } > @@ -2242,7 +2208,6 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id) > if (ret) { > amba_ports[i] = NULL; > uart_unregister_driver(&amba_reg); > - pl011_dma_remove(uap); > } > > return ret; just following up on this fix (the current driver is broken on my tests). Is it acceptable at this point?
On 03/03/2015 11:13 AM, Rob Herring wrote: > On Thu, Feb 26, 2015 at 10:56 AM, Jorge Ramirez-Ortiz > <jorge.ramirez-ortiz@linaro.org> wrote: >> 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. >> >> This commit allows for subsequent attempts to associate an external DMA if the >> DMA driver was deferred at UART hw_init time. >> >> Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org> > You need to send this to Greg KH and linux-serial if you want it applied. > > [...] ok. > >> @@ -261,10 +262,11 @@ 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 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); >> + struct device *const uap_dev = uap->port.dev; > Call this "dev" so you don't have all the needless renaming. > > With that change: > > Reviewed-by: Rob Herring <robh@kernel.org> OK. while I am at it, you initially suggested to do the probe in pl011_dma_startup. Instead I probed from pl011_hwinit since it matched the original behaviour of also probing the DMA when CONFIG_CONSOLE_POLL was enabled. However, since the CONFIG_CONSOLE_POLL implementation for the amba-pl011 doesn't use the DMA it actually doesn't help to keep it in pl011_hwinit. is it ok with you if I move this to pl011_dma_startup as you initially suggested? > >> + struct amba_pl011_data *plat = dev_get_platdata(uap_dev); >> struct dma_slave_config tx_conf = { >> .dst_addr = uap->port.mapbase + UART01x_DR, >> .dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE, >> @@ -275,12 +277,19 @@ 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(uap_dev, "tx"); >> + if (IS_ERR(chan)) { >> + if (PTR_ERR(chan) == -EPROBE_DEFER) { >> + dev_info(uap_dev, "DMA driver not ready\n"); >> + uap->dma_probed = false; >> + return; >> + } >> >> - if (!chan) { >> /* We need platform data */ >> if (!plat || !plat->dma_filter) { >> - dev_info(uap->port.dev, "no DMA platform data\n"); >> + dev_info(uap_dev, "no DMA platform data\n"); >> return; >> }amba-pl011.c >> >> @@ -291,7 +300,7 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port * >> chan = dma_request_channel(mask, plat->dma_filter, >> plat->dma_tx_param); >> if (!chan) { >> - dev_err(uap->port.dev, "no TX DMA channel!\n"); >> + dev_err(uap_dev, "no TX DMA channel!\n"); >> return; >> } >> } >> @@ -299,17 +308,17 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port * >> dmaengine_slave_config(chan, &tx_conf); >> uap->dmatx.chan = chan; >> >> - dev_info(uap->port.dev, "DMA channel TX %s\n", >> + dev_info(uap_dev, "DMA channel TX %s\n", >> dma_chan_name(uap->dmatx.chan)); >> >> /* Optionally make use of an RX channel as well */ >> - chan = dma_request_slave_channel(dev, "rx"); >> + chan = dma_request_slave_channel(uap_dev, "rx"); >> >> if (!chan && plat->dma_rx_param) { >> chan = dma_request_channel(mask, plat->dma_filter, plat->dma_rx_param); >> >> if (!chan) { >> - dev_err(uap->port.dev, "no RX DMA channel!\n"); >> + dev_err(uap_dev, "no RX DMA channel!\n"); >> return; >> } >> } >> @@ -333,7 +342,7 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port * >> if (caps.residue_granularity == >> DMA_RESIDUE_GRANULARITY_DESCRIPTOR) { >> dma_release_channel(chan); >> - dev_info(uap->port.dev, >> + dev_info(uap_dev, >> "RX DMA disabled - no residue processing\n"); >> return; >> } >> @@ -362,75 +371,29 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port * >> plat->dma_rx_poll_timeout; >> else >> uap->dmarx.poll_timeout = 3000; >> - } else if (!plat && dev->of_node) { >> + } else if (!plat && uap_dev->of_node) { >> uap->dmarx.auto_poll_rate = of_property_read_bool( >> - dev->of_node, "auto-poll"); >> + uap_dev->of_node, "auto-poll"); >> if (uap->dmarx.auto_poll_rate) { >> u32 x; >> >> - if (0 == of_property_read_u32(dev->of_node, >> + if (0 == of_property_read_u32(uap_dev->of_node, >> "poll-rate-ms", &x)) >> uap->dmarx.poll_rate = x; >> else >> uap->dmarx.poll_rate = 100; >> - if (0 == of_property_read_u32(dev->of_node, >> + if (0 == of_property_read_u32(uap_dev->of_node, >> "poll-timeout-ms", &x)) >> uap->dmarx.poll_timeout = x; >> else >> uap->dmarx.poll_timeout = 3000; >> } >> } >> - dev_info(uap->port.dev, "DMA channel RX %s\n", >> + dev_info(uap_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 */ >> @@ -1142,7 +1105,7 @@ 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 inline void pl011_dma_probe(struct uart_amba_port *uap) >> { >> } >> >> @@ -1548,6 +1511,9 @@ 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); >> + >> if (dev_get_platdata(uap->port.dev)) { >> struct amba_pl011_data *plat; >> >> @@ -2218,7 +2184,6 @@ 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); >> @@ -2233,7 +2198,8 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id) >> if (!amba_reg.state) { >> ret = uart_register_driver(&amba_reg); >> if (ret < 0) { >> - pr_err("Failed to register AMBA-PL011 driver\n"); >> + dev_err(&dev->dev, >> + "Failed to register AMBA-PL011 driver\n"); >> return ret; >> } >> } >> @@ -2242,7 +2208,6 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id) >> if (ret) { >> amba_ports[i] = NULL; >> uart_unregister_driver(&amba_reg); >> - pl011_dma_remove(uap); >> } >> >> return ret; >> -- >> 1.9.1 >>
On 03/09/2015 11:57 AM, Russell King - ARM Linux wrote: > On Tue, Mar 03, 2015 at 11:06:32AM -0500, Jorge Ramirez-Ortiz wrote: >> On 02/26/2015 11:56 AM, Jorge Ramirez-Ortiz wrote: >>> - chan = dma_request_slave_channel(dev, "tx"); >>> + uap->dma_probed = true; >>> + >>> + chan = dma_request_slave_channel_reason(uap_dev, "tx"); >>> + if (IS_ERR(chan)) { >>> + if (PTR_ERR(chan) == -EPROBE_DEFER) { >>> + dev_info(uap_dev, "DMA driver not ready\n"); > I still object to this. it was an oversight, not intentional. my fault. > > It _can't_ be right that we plaster the kernel console with these > messages when the is a DMA possible, but the DMA driver is a module > which hasn't been loaded yet. > > You probably don't realise it, but init daemons tend to open the > console, write their message, and then close it again. What your > message above means is that each time an init daemon does that, we > get a "DMA driver not ready" message. I initially - before your first remarks- did think about the init daemons and balancing the value I saw in having the message in (for product developers) I thought it was worth having it. What I didnt know relates to your second point about modules: - That for as long as the device tree declares a DMA name that matches the one that the UART requests in its DT settings, attempting to request a channel on it before said DMA driver has been registered would be returning EPROBE_DEFER (same thing for ACPI). - And yes, as the situation described above could go on for ever (maybe the driver was blacklisted) the clutter in the log would be unacceptable. [I had only looked at defer driver probing from the perspective of its internal lists (deferred_probe_ending/active_list) and did not have the overall picture in mind. So I missed this point] > > IMHO, that is unacceptable. > agree.
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c index 8d94c19..4ce98e9 100644 --- a/drivers/tty/serial/amba-pl011.c +++ b/drivers/tty/serial/amba-pl011.c @@ -164,6 +164,7 @@ struct uart_amba_port { bool using_rx_dma; struct pl011_dmarx_data dmarx; struct pl011_dmatx_data dmatx; + bool dma_probed; #endif }; @@ -261,10 +262,11 @@ 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 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); + struct device *const uap_dev = uap->port.dev; + struct amba_pl011_data *plat = dev_get_platdata(uap_dev); struct dma_slave_config tx_conf = { .dst_addr = uap->port.mapbase + UART01x_DR, .dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE, @@ -275,12 +277,19 @@ 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(uap_dev, "tx"); + if (IS_ERR(chan)) { + if (PTR_ERR(chan) == -EPROBE_DEFER) { + dev_info(uap_dev, "DMA driver not ready\n"); + uap->dma_probed = false; + return; + } - if (!chan) { /* We need platform data */ if (!plat || !plat->dma_filter) { - dev_info(uap->port.dev, "no DMA platform data\n"); + dev_info(uap_dev, "no DMA platform data\n"); return; } @@ -291,7 +300,7 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port * chan = dma_request_channel(mask, plat->dma_filter, plat->dma_tx_param); if (!chan) { - dev_err(uap->port.dev, "no TX DMA channel!\n"); + dev_err(uap_dev, "no TX DMA channel!\n"); return; } } @@ -299,17 +308,17 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port * dmaengine_slave_config(chan, &tx_conf); uap->dmatx.chan = chan; - dev_info(uap->port.dev, "DMA channel TX %s\n", + dev_info(uap_dev, "DMA channel TX %s\n", dma_chan_name(uap->dmatx.chan)); /* Optionally make use of an RX channel as well */ - chan = dma_request_slave_channel(dev, "rx"); + chan = dma_request_slave_channel(uap_dev, "rx"); if (!chan && plat->dma_rx_param) { chan = dma_request_channel(mask, plat->dma_filter, plat->dma_rx_param); if (!chan) { - dev_err(uap->port.dev, "no RX DMA channel!\n"); + dev_err(uap_dev, "no RX DMA channel!\n"); return; } } @@ -333,7 +342,7 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port * if (caps.residue_granularity == DMA_RESIDUE_GRANULARITY_DESCRIPTOR) { dma_release_channel(chan); - dev_info(uap->port.dev, + dev_info(uap_dev, "RX DMA disabled - no residue processing\n"); return; } @@ -362,75 +371,29 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port * plat->dma_rx_poll_timeout; else uap->dmarx.poll_timeout = 3000; - } else if (!plat && dev->of_node) { + } else if (!plat && uap_dev->of_node) { uap->dmarx.auto_poll_rate = of_property_read_bool( - dev->of_node, "auto-poll"); + uap_dev->of_node, "auto-poll"); if (uap->dmarx.auto_poll_rate) { u32 x; - if (0 == of_property_read_u32(dev->of_node, + if (0 == of_property_read_u32(uap_dev->of_node, "poll-rate-ms", &x)) uap->dmarx.poll_rate = x; else uap->dmarx.poll_rate = 100; - if (0 == of_property_read_u32(dev->of_node, + if (0 == of_property_read_u32(uap_dev->of_node, "poll-timeout-ms", &x)) uap->dmarx.poll_timeout = x; else uap->dmarx.poll_timeout = 3000; } } - dev_info(uap->port.dev, "DMA channel RX %s\n", + dev_info(uap_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 */ @@ -1142,7 +1105,7 @@ 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 inline void pl011_dma_probe(struct uart_amba_port *uap) { } @@ -1548,6 +1511,9 @@ 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); + if (dev_get_platdata(uap->port.dev)) { struct amba_pl011_data *plat; @@ -2218,7 +2184,6 @@ 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); @@ -2233,7 +2198,8 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id) if (!amba_reg.state) { ret = uart_register_driver(&amba_reg); if (ret < 0) { - pr_err("Failed to register AMBA-PL011 driver\n"); + dev_err(&dev->dev, + "Failed to register AMBA-PL011 driver\n"); return ret; } } @@ -2242,7 +2208,6 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id) if (ret) { amba_ports[i] = NULL; uart_unregister_driver(&amba_reg); - pl011_dma_remove(uap); } return ret;
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. This commit allows for subsequent attempts to associate an external DMA if the DMA driver was deferred at UART hw_init time. Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org> --- drivers/tty/serial/amba-pl011.c | 95 +++++++++++++---------------------------- 1 file changed, 30 insertions(+), 65 deletions(-)