ALSA: emu10k1: use mutex for E-MU FPGA access locking

The FPGA access through the GPIO port does not interfere with other
sound processor register access, so there is no need to subject it to
emu_lock. And after moving all FPGA access out of the interrupt handler,
it does not need to be IRQ-safe, either.

What's more, attaching the dock causes a firmware upload, which takes
several seconds. We really don't want to disable IRQs for this long, and
even less also have someone else spin with IRQs disabled waiting for us.

Therefore, use a mutex for FPGA access locking.

This makes the code somewhat more noisy, as we need to wrap bigger
sections into the mutex, as it needs to enclose the spinlocks.

The latter has the "side effect" of fixing dock FPGA programming in a
corner case: a really badly timed mixer access right between entering
FPGA programming mode and uploading the netlist would mess up the
protocol.
Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Message-ID: <20240428093716.3198666-5-oswald.buddenhagen@gmx.de>

include/sound/emu10k1.h

@@ -1685,6 +1685,7 @@ struct snd_emu1010 {
 	unsigned int optical_in; /* 0:SPDIF, 1:ADAT */
 	unsigned int optical_out; /* 0:SPDIF, 1:ADAT */
 	struct work_struct work;
+	struct mutex lock;
 };
 
 struct snd_emu10k1 {
@@ -1833,6 +1834,9 @@ unsigned int snd_emu10k1_ptr20_read(struct snd_emu10k1 * emu, unsigned int reg,
 void snd_emu10k1_ptr20_write(struct snd_emu10k1 *emu, unsigned int reg, unsigned int chn, unsigned int data);
 int snd_emu10k1_spi_write(struct snd_emu10k1 * emu, unsigned int data);
 int snd_emu10k1_i2c_write(struct snd_emu10k1 *emu, u32 reg, u32 value);
+static inline void snd_emu1010_fpga_lock(struct snd_emu10k1 *emu) { mutex_lock(&emu->emu1010.lock); };
+static inline void snd_emu1010_fpga_unlock(struct snd_emu10k1 *emu) { mutex_unlock(&emu->emu1010.lock); };
+void snd_emu1010_fpga_write_lock(struct snd_emu10k1 *emu, u32 reg, u32 value);
 void snd_emu1010_fpga_write(struct snd_emu10k1 *emu, u32 reg, u32 value);
 void snd_emu1010_fpga_read(struct snd_emu10k1 *emu, u32 reg, u32 *value);
 void snd_emu1010_fpga_link_dst_src_write(struct snd_emu10k1 *emu, u32 dst, u32 src);

sound/pci/emu10k1/emu10k1_main.c

@@ -810,6 +810,8 @@ static void emu1010_work(struct work_struct *work)
 		return;
 #endif
 
+	snd_emu1010_fpga_lock(emu);
+
 	snd_emu1010_fpga_read(emu, EMU_HANA_IRQ_STATUS, &sts);
 
 	// The distinction of the IRQ status bits is unreliable,
@@ -819,6 +821,8 @@ static void emu1010_work(struct work_struct *work)
 
 	if (sts & EMU_HANA_IRQ_WCLK_CHANGED)
 		emu1010_clock_event(emu);
+
+	snd_emu1010_fpga_unlock(emu);
 }
 
 static void emu1010_interrupt(struct snd_emu10k1 *emu)
@@ -852,6 +856,8 @@ static int snd_emu10k1_emu1010_init(struct snd_emu10k1 *emu)
 	 * Proper init follows in snd_emu10k1_init(). */
 	outl(HCFG_LOCKSOUNDCACHE | HCFG_LOCKTANKCACHE_MASK, emu->port + HCFG);
 
+	snd_emu1010_fpga_lock(emu);
+
 	/* Disable 48Volt power to Audio Dock */
 	snd_emu1010_fpga_write(emu, EMU_HANA_DOCK_PWR, 0);
 
@@ -877,7 +883,7 @@ static int snd_emu10k1_emu1010_init(struct snd_emu10k1 *emu)
 	err = snd_emu1010_load_firmware(emu, 0, &emu->firmware);
 	if (err < 0) {
 		dev_info(emu->card->dev, "emu1010: Loading Firmware failed\n");
-		return err;
+		goto fail;
 	}
 
 	/* ID, should read & 0x7f = 0x55 when FPGA programmed. */
@@ -887,7 +893,8 @@ static int snd_emu10k1_emu1010_init(struct snd_emu10k1 *emu)
 		dev_info(emu->card->dev,
 			 "emu1010: Loading Hana Firmware file failed, reg = 0x%x\n",
 			 reg);
-		return -ENODEV;
+		err = -ENODEV;
+		goto fail;
 	}
 
 	dev_info(emu->card->dev, "emu1010: Hana Firmware loaded\n");
@@ -947,7 +954,9 @@ static int snd_emu10k1_emu1010_init(struct snd_emu10k1 *emu)
 	// so it is safe to simply enable the outputs.
 	snd_emu1010_fpga_write(emu, EMU_HANA_UNMUTE, EMU_UNMUTE);
 
-	return 0;
+fail:
+	snd_emu1010_fpga_unlock(emu);
+	return err;
 }
 /*
  *  Create the EMU10K1 instance
@@ -969,9 +978,10 @@ static void snd_emu10k1_free(struct snd_card *card)
 	}
 	if (emu->card_capabilities->emu_model == EMU_MODEL_EMU1010) {
 		/* Disable 48Volt power to Audio Dock */
-		snd_emu1010_fpga_write(emu, EMU_HANA_DOCK_PWR, 0);
+		snd_emu1010_fpga_write_lock(emu, EMU_HANA_DOCK_PWR, 0);
 	}
 	cancel_work_sync(&emu->emu1010.work);
+	mutex_destroy(&emu->emu1010.lock);
 	release_firmware(emu->firmware);
 	release_firmware(emu->dock_fw);
 	snd_util_memhdr_free(emu->memhdr);
@@ -1551,6 +1561,7 @@ int snd_emu10k1_create(struct snd_card *card,
 	emu->synth = NULL;
 	emu->get_synth_voice = NULL;
 	INIT_WORK(&emu->emu1010.work, emu1010_work);
+	mutex_init(&emu->emu1010.lock);
 	/* read revision & serial */
 	emu->revision = pci->revision;
 	pci_read_config_dword(pci, PCI_SUBSYSTEM_VENDOR_ID, &emu->serial);

sound/pci/emu10k1/emumixer.c

@@ -661,7 +661,9 @@ static int snd_emu1010_output_source_put(struct snd_kcontrol *kcontrol,
 	change = (emu->emu1010.output_source[channel] != val);
 	if (change) {
 		emu->emu1010.output_source[channel] = val;
+		snd_emu1010_fpga_lock(emu);
 		snd_emu1010_output_source_apply(emu, channel, val);
+		snd_emu1010_fpga_unlock(emu);
 	}
 	return change;
 }
@@ -705,7 +707,9 @@ static int snd_emu1010_input_source_put(struct snd_kcontrol *kcontrol,
 	change = (emu->emu1010.input_source[channel] != val);
 	if (change) {
 		emu->emu1010.input_source[channel] = val;
+		snd_emu1010_fpga_lock(emu);
 		snd_emu1010_input_source_apply(emu, channel, val);
+		snd_emu1010_fpga_unlock(emu);
 	}
 	return change;
 }
@@ -774,7 +778,7 @@ static int snd_emu1010_adc_pads_put(struct snd_kcontrol *kcontrol, struct snd_ct
 		cache = cache & ~mask;
 	change = (cache != emu->emu1010.adc_pads);
 	if (change) {
-		snd_emu1010_fpga_write(emu, EMU_HANA_ADC_PADS, cache );
+		snd_emu1010_fpga_write_lock(emu, EMU_HANA_ADC_PADS, cache );
 	        emu->emu1010.adc_pads = cache;
 	}
 
@@ -832,7 +836,7 @@ static int snd_emu1010_dac_pads_put(struct snd_kcontrol *kcontrol, struct snd_ct
 		cache = cache & ~mask;
 	change = (cache != emu->emu1010.dac_pads);
 	if (change) {
-		snd_emu1010_fpga_write(emu, EMU_HANA_DAC_PADS, cache );
+		snd_emu1010_fpga_write_lock(emu, EMU_HANA_DAC_PADS, cache );
 	        emu->emu1010.dac_pads = cache;
 	}
 
@@ -980,6 +984,7 @@ static int snd_emu1010_clock_source_put(struct snd_kcontrol *kcontrol,
 	val = ucontrol->value.enumerated.item[0] ;
 	if (val >= emu_ci->num)
 		return -EINVAL;
+	snd_emu1010_fpga_lock(emu);
 	spin_lock_irq(&emu->reg_lock);
 	change = (emu->emu1010.clock_source != val);
 	if (change) {
@@ -996,6 +1001,7 @@ static int snd_emu1010_clock_source_put(struct snd_kcontrol *kcontrol,
 	} else {
 		spin_unlock_irq(&emu->reg_lock);
 	}
+	snd_emu1010_fpga_unlock(emu);
 	return change;
 }
 
@@ -1041,7 +1047,7 @@ static int snd_emu1010_clock_fallback_put(struct snd_kcontrol *kcontrol,
 	change = (emu->emu1010.clock_fallback != val);
 	if (change) {
 		emu->emu1010.clock_fallback = val;
-		snd_emu1010_fpga_write(emu, EMU_HANA_DEFCLOCK, 1 - val);
+		snd_emu1010_fpga_write_lock(emu, EMU_HANA_DEFCLOCK, 1 - val);
 	}
 	return change;
 }
@@ -1093,7 +1099,7 @@ static int snd_emu1010_optical_out_put(struct snd_kcontrol *kcontrol,
 		emu->emu1010.optical_out = val;
 		tmp = (emu->emu1010.optical_in ? EMU_HANA_OPTICAL_IN_ADAT : EMU_HANA_OPTICAL_IN_SPDIF) |
 			(emu->emu1010.optical_out ? EMU_HANA_OPTICAL_OUT_ADAT : EMU_HANA_OPTICAL_OUT_SPDIF);
-		snd_emu1010_fpga_write(emu, EMU_HANA_OPTICAL_TYPE, tmp);
+		snd_emu1010_fpga_write_lock(emu, EMU_HANA_OPTICAL_TYPE, tmp);
 	}
 	return change;
 }
@@ -1144,7 +1150,7 @@ static int snd_emu1010_optical_in_put(struct snd_kcontrol *kcontrol,
 		emu->emu1010.optical_in = val;
 		tmp = (emu->emu1010.optical_in ? EMU_HANA_OPTICAL_IN_ADAT : EMU_HANA_OPTICAL_IN_SPDIF) |
 			(emu->emu1010.optical_out ? EMU_HANA_OPTICAL_OUT_ADAT : EMU_HANA_OPTICAL_OUT_SPDIF);
-		snd_emu1010_fpga_write(emu, EMU_HANA_OPTICAL_TYPE, tmp);
+		snd_emu1010_fpga_write_lock(emu, EMU_HANA_OPTICAL_TYPE, tmp);
 	}
 	return change;
 }
@@ -2323,7 +2329,9 @@ int snd_emu10k1_mixer(struct snd_emu10k1 *emu,
 		for (i = 0; i < emu_ri->n_outs; i++)
 			emu->emu1010.output_source[i] =
 				emu1010_map_source(emu_ri, emu_ri->out_dflts[i]);
+		snd_emu1010_fpga_lock(emu);
 		snd_emu1010_apply_sources(emu);
+		snd_emu1010_fpga_unlock(emu);
 
 		kctl = emu->ctl_clock_source = snd_ctl_new1(&snd_emu1010_clock_source, emu);
 		err = snd_ctl_add(card, kctl);

sound/pci/emu10k1/emuproc.c

@@ -165,6 +165,8 @@ static void snd_emu10k1_proc_spdif_read(struct snd_info_entry *entry,
 	u32 value2;
 
 	if (emu->card_capabilities->emu_model) {
+		snd_emu1010_fpga_lock(emu);
+
 		// This represents the S/PDIF lock status on 0404b, which is
 		// kinda weird and unhelpful, because monitoring it via IRQ is
 		// impractical (one gets an IRQ flood as long as it is desynced).
@@ -197,6 +199,8 @@ static void snd_emu10k1_proc_spdif_read(struct snd_info_entry *entry,
 			snd_iprintf(buffer, "\nS/PDIF mode: %s%s\n",
 				    value & EMU_HANA_SPDIF_MODE_RX_PRO ? "professional" : "consumer",
 				    value & EMU_HANA_SPDIF_MODE_RX_NOCOPY ? ", no copy" : "");
+
+		snd_emu1010_fpga_unlock(emu);
 	} else {
 		snd_emu10k1_proc_spdif_status(emu, buffer, "CD-ROM S/PDIF In", CDCS, CDSRCS);
 		snd_emu10k1_proc_spdif_status(emu, buffer, "Optical or Coax S/PDIF In", GPSCS, GPSRCS);
@@ -458,6 +462,9 @@ static void snd_emu_proc_emu1010_reg_read(struct snd_info_entry *entry,
 	struct snd_emu10k1 *emu = entry->private_data;
 	u32 value;
 	int i;
+
+	snd_emu1010_fpga_lock(emu);
+
 	snd_iprintf(buffer, "EMU1010 Registers:\n\n");
 
 	for(i = 0; i < 0x40; i+=1) {
@@ -496,6 +503,8 @@ static void snd_emu_proc_emu1010_reg_read(struct snd_info_entry *entry,
 			snd_emu_proc_emu1010_link_read(emu, buffer, 0x701);
 		}
 	}
+
+	snd_emu1010_fpga_unlock(emu);
 }
 
 static void snd_emu_proc_io_reg_read(struct snd_info_entry *entry,

sound/pci/emu10k1/io.c

@@ -289,20 +289,28 @@ static void snd_emu1010_fpga_write_locked(struct snd_emu10k1 *emu, u32 reg, u32
 
 void snd_emu1010_fpga_write(struct snd_emu10k1 *emu, u32 reg, u32 value)
 {
-	unsigned long flags;
+	if (snd_BUG_ON(!mutex_is_locked(&emu->emu1010.lock)))
+		return;
+	snd_emu1010_fpga_write_locked(emu, reg, value);
+}
 
-	spin_lock_irqsave(&emu->emu_lock, flags);
+void snd_emu1010_fpga_write_lock(struct snd_emu10k1 *emu, u32 reg, u32 value)
+{
+	snd_emu1010_fpga_lock(emu);
 	snd_emu1010_fpga_write_locked(emu, reg, value);
-	spin_unlock_irqrestore(&emu->emu_lock, flags);
+	snd_emu1010_fpga_unlock(emu);
 }
 
-static void snd_emu1010_fpga_read_locked(struct snd_emu10k1 *emu, u32 reg, u32 *value)
+void snd_emu1010_fpga_read(struct snd_emu10k1 *emu, u32 reg, u32 *value)
 {
 	// The higest input pin is used as the designated interrupt trigger,
 	// so it needs to be masked out.
 	// But note that any other input pin change will also cause an IRQ,
 	// so using this function often causes an IRQ as a side effect.
 	u32 mask = emu->card_capabilities->ca0108_chip ? 0x1f : 0x7f;
+
+	if (snd_BUG_ON(!mutex_is_locked(&emu->emu1010.lock)))
+		return;
 	if (snd_BUG_ON(reg > 0x3f))
 		return;
 	reg += 0x40; /* 0x40 upwards are registers. */
@@ -313,47 +321,31 @@ static void snd_emu1010_fpga_read_locked(struct snd_emu10k1 *emu, u32 reg, u32 *
 	*value = ((inw(emu->port + A_GPIO) >> 8) & mask);
 }
 
-void snd_emu1010_fpga_read(struct snd_emu10k1 *emu, u32 reg, u32 *value)
-{
-	unsigned long flags;
-
-	spin_lock_irqsave(&emu->emu_lock, flags);
-	snd_emu1010_fpga_read_locked(emu, reg, value);
-	spin_unlock_irqrestore(&emu->emu_lock, flags);
-}
-
 /* Each Destination has one and only one Source,
  * but one Source can feed any number of Destinations simultaneously.
  */
 void snd_emu1010_fpga_link_dst_src_write(struct snd_emu10k1 *emu, u32 dst, u32 src)
 {
-	unsigned long flags;
-
 	if (snd_BUG_ON(dst & ~0x71f))
 		return;
 	if (snd_BUG_ON(src & ~0x71f))
 		return;
-	spin_lock_irqsave(&emu->emu_lock, flags);
-	snd_emu1010_fpga_write_locked(emu, EMU_HANA_DESTHI, dst >> 8);
-	snd_emu1010_fpga_write_locked(emu, EMU_HANA_DESTLO, dst & 0x1f);
-	snd_emu1010_fpga_write_locked(emu, EMU_HANA_SRCHI, src >> 8);
-	snd_emu1010_fpga_write_locked(emu, EMU_HANA_SRCLO, src & 0x1f);
-	spin_unlock_irqrestore(&emu->emu_lock, flags);
+	snd_emu1010_fpga_write(emu, EMU_HANA_DESTHI, dst >> 8);
+	snd_emu1010_fpga_write(emu, EMU_HANA_DESTLO, dst & 0x1f);
+	snd_emu1010_fpga_write(emu, EMU_HANA_SRCHI, src >> 8);
+	snd_emu1010_fpga_write(emu, EMU_HANA_SRCLO, src & 0x1f);
 }
 
 u32 snd_emu1010_fpga_link_dst_src_read(struct snd_emu10k1 *emu, u32 dst)
 {
-	unsigned long flags;
 	u32 hi, lo;
 
 	if (snd_BUG_ON(dst & ~0x71f))
 		return 0;
-	spin_lock_irqsave(&emu->emu_lock, flags);
-	snd_emu1010_fpga_write_locked(emu, EMU_HANA_DESTHI, dst >> 8);
-	snd_emu1010_fpga_write_locked(emu, EMU_HANA_DESTLO, dst & 0x1f);
-	snd_emu1010_fpga_read_locked(emu, EMU_HANA_SRCHI, &hi);
-	snd_emu1010_fpga_read_locked(emu, EMU_HANA_SRCLO, &lo);
-	spin_unlock_irqrestore(&emu->emu_lock, flags);
+	snd_emu1010_fpga_write(emu, EMU_HANA_DESTHI, dst >> 8);
+	snd_emu1010_fpga_write(emu, EMU_HANA_DESTLO, dst & 0x1f);
+	snd_emu1010_fpga_read(emu, EMU_HANA_SRCHI, &hi);
+	snd_emu1010_fpga_read(emu, EMU_HANA_SRCLO, &lo);
 	return (hi << 8) | lo;
 }