diff mbox series

[v2] Bluetooth: btintel: Allow lowering of drive strength of BRI

Message ID 20240621064419.2185652-1-kiran.k@intel.com
State New
Headers show
Series [v2] Bluetooth: btintel: Allow lowering of drive strength of BRI | expand

Commit Message

K, Kiran June 21, 2024, 6:44 a.m. UTC
BRI (Bluetooth Radio Interface) traffic from CNVr to CNVi was found
causing cross talk step errors to WiFi. As a workaround, driver needs to
reduce the drive strength of BRI. During *setup*, driver reads the drive
strength value from efi variable and passes it controller via vendor
specific command with opcode 0xfc0a.

Signed-off-by: Kiran K <kiran.k@intel.com>
---
 drivers/bluetooth/btintel.c | 114 ++++++++++++++++++++++++++++++++++++
 1 file changed, 114 insertions(+)

Comments

Paul Menzel June 21, 2024, 7:16 a.m. UTC | #1
Dear Kiran,


Thank you for the patch.


Am 21.06.24 um 08:44 schrieb Kiran K:
> BRI (Bluetooth Radio Interface) traffic from CNVr to CNVi was found
> causing cross talk step errors to WiFi.

Interesting. Can you please elaborate how that can be detected?

> As a workaround, driver needs to
> reduce the drive strength of BRI. During *setup*, driver reads the drive
> strength value from efi variable and passes it controller via vendor

Where is this EFI variable described?

… passes it *to the* controller …

> specific command with opcode 0xfc0a.

Please document your test system and also add the new log messages.

> Signed-off-by: Kiran K <kiran.k@intel.com>
> ---
>   drivers/bluetooth/btintel.c | 114 ++++++++++++++++++++++++++++++++++++
>   1 file changed, 114 insertions(+)
> 
> diff --git a/drivers/bluetooth/btintel.c b/drivers/bluetooth/btintel.c
> index 5d735391545a..3dc557aac43d 100644
> --- a/drivers/bluetooth/btintel.c
> +++ b/drivers/bluetooth/btintel.c
> @@ -12,6 +12,8 @@
>   #include <linux/acpi.h>
>   #include <acpi/acpi_bus.h>
>   #include <asm/unaligned.h>
> +#include <linux/efi.h>
> +
>   
>   #include <net/bluetooth/bluetooth.h>
>   #include <net/bluetooth/hci_core.h>
> @@ -49,6 +51,38 @@ static const guid_t btintel_guid_dsm =
>   	GUID_INIT(0xaa10f4e0, 0x81ac, 0x4233,
>   		  0xab, 0xf6, 0x3b, 0x2a, 0xc5, 0x0e, 0x28, 0xd9);
>   
> +static void *btintel_uefi_get_variable(efi_char16_t *name, efi_guid_t *guid)
> +{
> +	void *data;
> +	efi_status_t status;
> +	size_t data_size = 0;
> +
> +	if (!IS_ENABLED(CONFIG_EFI))
> +		return ERR_PTR(-EOPNOTSUPP);
> +
> +	if (!efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE))
> +		return ERR_PTR(-EOPNOTSUPP);
> +
> +	status = efi.get_variable(name, guid, NULL, &data_size, NULL);
> +
> +	if (status != EFI_BUFFER_TOO_SMALL || !data_size)
> +		return ERR_PTR(-EIO);
> +
> +	data = kmalloc(data_size, GFP_KERNEL);
> +
> +	if (!data)
> +		return ERR_PTR(-ENOMEM);
> +
> +	status = efi.get_variable(name, guid, NULL, &data_size, data);
> +
> +	if (status != EFI_SUCCESS) {
> +		kfree(data);
> +		return ERR_PTR(-ENXIO);
> +	}
> +
> +	return data;
> +}
> +
>   int btintel_check_bdaddr(struct hci_dev *hdev)
>   {
>   	struct hci_rp_read_bd_addr *bda;
> @@ -2615,6 +2649,80 @@ static u8 btintel_classify_pkt_type(struct hci_dev *hdev, struct sk_buff *skb)
>   	return hci_skb_pkt_type(skb);
>   }
>   
> +static int btintel_set_dsbr(struct hci_dev *hdev, struct intel_version_tlv *ver)

Add a comment, what dsbr is?

> +{
> +	struct btintel_dsbr_cmd {
> +		u8 enable;
> +		u8 dsbr;
> +	} __packed;
> +
> +	struct btintel_dsbr {
> +		u8 header;
> +		u32 dsbr;
> +	} __packed;
> +
> +	struct btintel_dsbr *dsbr;
> +	struct btintel_dsbr_cmd cmd;
> +	struct sk_buff *skb;
> +	u8 status;
> +	efi_guid_t guid = EFI_GUID(0xe65d8884, 0xd4af, 0x4b20, 0x8d, 0x03,
> +				   0x77, 0x2e, 0xcc, 0x3d, 0xa5, 0x31);
> +
> +	memset(&cmd, 0, sizeof(cmd));
> +	dsbr = btintel_uefi_get_variable(L"UefiCnvCommonDSBR", &guid);
> +	if (IS_ERR(dsbr)) {
> +		/* If efi variable is not present, driver still needs to send
> +		 * 0xfc0a command with default values
> +		 */
> +		bt_dev_dbg(hdev, "Error reading efi DSBR (%ld)",

Maybe: Error reading EFI variable UefiCnvCommonDSBR (%ld)

> +			   PTR_ERR(dsbr));
> +		dsbr = NULL;
> +	}
> +
> +	if (dsbr) {
> +		/* bit0: 0 - Use firmware default value
> +		 *       1 - Override firmware value
> +		 * bit3:1 - Reserved
> +		 * bit7:4 - DSBR override values
> +		 * bt31:7 - Reserved
> +		 */
> +		cmd.enable = dsbr->dsbr & BIT(0);
> +		if (cmd.enable)
> +			cmd.dsbr = dsbr->dsbr >> 4 & 0xF;
> +		kfree(dsbr);
> +	}
> +
> +	bt_dev_info(hdev, "dsbr: enabled: 0x%2.2x value: 0x%2.2x", cmd.enable,
> +		    cmd.dsbr);
> +
> +	skb = __hci_cmd_sync(hdev, 0xfc0a, sizeof(cmd), &cmd,  HCI_CMD_TIMEOUT);
> +	if (IS_ERR(skb)) {
> +		bt_dev_err(hdev, "Failed to send Intel DSBR command (%ld)",
> +			   PTR_ERR(skb));
> +		return -bt_to_errno(PTR_ERR(skb));
> +	}
> +
> +	status = skb->data[0];
> +	kfree_skb(skb);
> +
> +	if (status) {
> +		bt_dev_err(hdev, "Set DSBR failed 0x%2.2x", status);
> +		return -bt_to_errno(status);
> +	}
> +	return 0;
> +}
> +
> +static int btintel_apply_dsbr(struct hci_dev *hdev,
> +			      struct intel_version_tlv *ver)
> +{
> +	/* For BlazarI + B0 step, DSBR command needs to be sent just after
> +	 * downloading IML firmware

Add the section of the datasheet?

> +	 */
> +	return ver->img_type == BTINTEL_IMG_IML &&
> +		((ver->cnvi_top & 0xfff) == BTINTEL_CNVI_BLAZARI) &&
> +		INTEL_CNVX_TOP_STEP(ver->cnvi_top) == 0x01;
> +}
> +
>   int btintel_bootloader_setup_tlv(struct hci_dev *hdev,
>   				 struct intel_version_tlv *ver)
>   {
> @@ -2649,6 +2757,12 @@ int btintel_bootloader_setup_tlv(struct hci_dev *hdev,
>   	if (err)
>   		return err;
>   
> +	if (btintel_apply_dsbr(hdev, ver)) {
> +		err = btintel_set_dsbr(hdev, ver);
> +		if (err)
> +			return err;
> +	}
> +
>   	/* If image type returned is BTINTEL_IMG_IML, then controller supports
>   	 * intermediae loader image
>   	 */


Kind regards,

Paul
K, Kiran June 24, 2024, 8:09 a.m. UTC | #2
Hi Paul,

Thanks for your comments.

>-----Original Message-----
>From: Paul Menzel <pmenzel@molgen.mpg.de>
>Sent: Friday, June 21, 2024 12:46 PM
>To: K, Kiran <kiran.k@intel.com>
>Cc: Srivatsa, Ravishankar <ravishankar.srivatsa@intel.com>; Tumkur Narayan,
>Chethan <chethan.tumkur.narayan@intel.com>; Devegowda, Chandrashekar
><chandrashekar.devegowda@intel.com>; Satija, Vijay <vijay.satija@intel.com>;
>linux-bluetooth@vger.kernel.org
>Subject: Re: [PATCH v2] Bluetooth: btintel: Allow lowering of drive strength of
>BRI
>
>Dear Kiran,
>
>
>Thank you for the patch.
>
>
>Am 21.06.24 um 08:44 schrieb Kiran K:
>> BRI (Bluetooth Radio Interface) traffic from CNVr to CNVi was found
>> causing cross talk step errors to WiFi.
>
>Interesting. Can you please elaborate how that can be detected?

Packet errors -  Need special hardware to detect this issue.

>
>> As a workaround, driver needs to
>> reduce the drive strength of BRI. During *setup*, driver reads the
>> drive strength value from efi variable and passes it controller via
>> vendor
>
>Where is this EFI variable described?
https://www.kernel.org/doc/html//v5.13/filesystems/efivarfs.html

>
>… passes it *to the* controller …
Ack.

>
>> specific command with opcode 0xfc0a.
>
>Please document your test system and also add the new log messages.
Ack.

> 
>> Signed-off-by: Kiran K <kiran.k@intel.com>
>> ---
>>   drivers/bluetooth/btintel.c | 114
>++++++++++++++++++++++++++++++++++++
>>   1 file changed, 114 insertions(+)
>>
>> diff --git a/drivers/bluetooth/btintel.c b/drivers/bluetooth/btintel.c
>> index 5d735391545a..3dc557aac43d 100644
>> --- a/drivers/bluetooth/btintel.c
>> +++ b/drivers/bluetooth/btintel.c
>> @@ -12,6 +12,8 @@
>>   #include <linux/acpi.h>
>>   #include <acpi/acpi_bus.h>
>>   #include <asm/unaligned.h>
>> +#include <linux/efi.h>
>> +
>>
>>   #include <net/bluetooth/bluetooth.h>
>>   #include <net/bluetooth/hci_core.h>
>> @@ -49,6 +51,38 @@ static const guid_t btintel_guid_dsm =
>>   	GUID_INIT(0xaa10f4e0, 0x81ac, 0x4233,
>>   		  0xab, 0xf6, 0x3b, 0x2a, 0xc5, 0x0e, 0x28, 0xd9);
>>
>> +static void *btintel_uefi_get_variable(efi_char16_t *name, efi_guid_t
>> +*guid) {
>> +	void *data;
>> +	efi_status_t status;
>> +	size_t data_size = 0;
>> +
>> +	if (!IS_ENABLED(CONFIG_EFI))
>> +		return ERR_PTR(-EOPNOTSUPP);
>> +
>> +	if (!efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE))
>> +		return ERR_PTR(-EOPNOTSUPP);
>> +
>> +	status = efi.get_variable(name, guid, NULL, &data_size, NULL);
>> +
>> +	if (status != EFI_BUFFER_TOO_SMALL || !data_size)
>> +		return ERR_PTR(-EIO);
>> +
>> +	data = kmalloc(data_size, GFP_KERNEL);
>> +
>> +	if (!data)
>> +		return ERR_PTR(-ENOMEM);
>> +
>> +	status = efi.get_variable(name, guid, NULL, &data_size, data);
>> +
>> +	if (status != EFI_SUCCESS) {
>> +		kfree(data);
>> +		return ERR_PTR(-ENXIO);
>> +	}
>> +
>> +	return data;
>> +}
>> +
>>   int btintel_check_bdaddr(struct hci_dev *hdev)
>>   {
>>   	struct hci_rp_read_bd_addr *bda;
>> @@ -2615,6 +2649,80 @@ static u8 btintel_classify_pkt_type(struct hci_dev
>*hdev, struct sk_buff *skb)
>>   	return hci_skb_pkt_type(skb);
>>   }
>>
>> +static int btintel_set_dsbr(struct hci_dev *hdev, struct
>> +intel_version_tlv *ver)
>
>Add a comment, what dsbr is?
Ack.

>
>> +{
>> +	struct btintel_dsbr_cmd {
>> +		u8 enable;
>> +		u8 dsbr;
>> +	} __packed;
>> +
>> +	struct btintel_dsbr {
>> +		u8 header;
>> +		u32 dsbr;
>> +	} __packed;
>> +
>> +	struct btintel_dsbr *dsbr;
>> +	struct btintel_dsbr_cmd cmd;
>> +	struct sk_buff *skb;
>> +	u8 status;
>> +	efi_guid_t guid = EFI_GUID(0xe65d8884, 0xd4af, 0x4b20, 0x8d, 0x03,
>> +				   0x77, 0x2e, 0xcc, 0x3d, 0xa5, 0x31);
>> +
>> +	memset(&cmd, 0, sizeof(cmd));
>> +	dsbr = btintel_uefi_get_variable(L"UefiCnvCommonDSBR", &guid);
>> +	if (IS_ERR(dsbr)) {
>> +		/* If efi variable is not present, driver still needs to send
>> +		 * 0xfc0a command with default values
>> +		 */
>> +		bt_dev_dbg(hdev, "Error reading efi DSBR (%ld)",
>
>Maybe: Error reading EFI variable UefiCnvCommonDSBR (%ld)
Ack.

>
>> +			   PTR_ERR(dsbr));
>> +		dsbr = NULL;
>> +	}
>> +
>> +	if (dsbr) {
>> +		/* bit0: 0 - Use firmware default value
>> +		 *       1 - Override firmware value
>> +		 * bit3:1 - Reserved
>> +		 * bit7:4 - DSBR override values
>> +		 * bt31:7 - Reserved
>> +		 */
>> +		cmd.enable = dsbr->dsbr & BIT(0);
>> +		if (cmd.enable)
>> +			cmd.dsbr = dsbr->dsbr >> 4 & 0xF;
>> +		kfree(dsbr);
>> +	}
>> +
>> +	bt_dev_info(hdev, "dsbr: enabled: 0x%2.2x value: 0x%2.2x",
>cmd.enable,
>> +		    cmd.dsbr);
>> +
>> +	skb = __hci_cmd_sync(hdev, 0xfc0a, sizeof(cmd), &cmd,
>HCI_CMD_TIMEOUT);
>> +	if (IS_ERR(skb)) {
>> +		bt_dev_err(hdev, "Failed to send Intel DSBR command (%ld)",
>> +			   PTR_ERR(skb));
>> +		return -bt_to_errno(PTR_ERR(skb));
>> +	}
>> +
>> +	status = skb->data[0];
>> +	kfree_skb(skb);
>> +
>> +	if (status) {
>> +		bt_dev_err(hdev, "Set DSBR failed 0x%2.2x", status);
>> +		return -bt_to_errno(status);
>> +	}
>> +	return 0;
>> +}
>> +
>> +static int btintel_apply_dsbr(struct hci_dev *hdev,
>> +			      struct intel_version_tlv *ver) {
>> +	/* For BlazarI + B0 step, DSBR command needs to be sent just after
>> +	 * downloading IML firmware
>
>Add the section of the datasheet?
>
>> +	 */
>> +	return ver->img_type == BTINTEL_IMG_IML &&
>> +		((ver->cnvi_top & 0xfff) == BTINTEL_CNVI_BLAZARI) &&
>> +		INTEL_CNVX_TOP_STEP(ver->cnvi_top) == 0x01; }
>> +
>>   int btintel_bootloader_setup_tlv(struct hci_dev *hdev,
>>   				 struct intel_version_tlv *ver)
>>   {
>> @@ -2649,6 +2757,12 @@ int btintel_bootloader_setup_tlv(struct hci_dev
>*hdev,
>>   	if (err)
>>   		return err;
>>
>> +	if (btintel_apply_dsbr(hdev, ver)) {
>> +		err = btintel_set_dsbr(hdev, ver);
>> +		if (err)
>> +			return err;
>> +	}
>> +
>>   	/* If image type returned is BTINTEL_IMG_IML, then controller
>supports
>>   	 * intermediae loader image
>>   	 */
>
>
>Kind regards,
>
>Paul

Thanks,
Kiran
kernel test robot June 25, 2024, 10:40 p.m. UTC | #3
Hi Kiran,

kernel test robot noticed the following build errors:

[auto build test ERROR on bluetooth-next/master]
[also build test ERROR on next-20240625]
[cannot apply to bluetooth/master linus/master v6.10-rc5]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Kiran-K/Bluetooth-btintel-Allow-lowering-of-drive-strength-of-BRI/20240625-161151
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth-next.git master
patch link:    https://lore.kernel.org/r/20240621064419.2185652-1-kiran.k%40intel.com
patch subject: [PATCH v2] Bluetooth: btintel: Allow lowering of drive strength of BRI
config: m68k-allmodconfig (https://download.01.org/0day-ci/archive/20240626/202406260659.fzB4yn3X-lkp@intel.com/config)
compiler: m68k-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240626/202406260659.fzB4yn3X-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202406260659.fzB4yn3X-lkp@intel.com/

All errors (new ones prefixed by >>):

   drivers/bluetooth/btintel.c: In function 'btintel_uefi_get_variable':
>> drivers/bluetooth/btintel.c:66:53: error: passing argument 4 of 'efi.get_variable' from incompatible pointer type [-Werror=incompatible-pointer-types]
      66 |         status = efi.get_variable(name, guid, NULL, &data_size, NULL);
         |                                                     ^~~~~~~~~~
         |                                                     |
         |                                                     size_t * {aka unsigned int *}
   drivers/bluetooth/btintel.c:66:53: note: expected 'long unsigned int *' but argument is of type 'size_t *' {aka 'unsigned int *'}
   drivers/bluetooth/btintel.c:76:53: error: passing argument 4 of 'efi.get_variable' from incompatible pointer type [-Werror=incompatible-pointer-types]
      76 |         status = efi.get_variable(name, guid, NULL, &data_size, data);
         |                                                     ^~~~~~~~~~
         |                                                     |
         |                                                     size_t * {aka unsigned int *}
   drivers/bluetooth/btintel.c:76:53: note: expected 'long unsigned int *' but argument is of type 'size_t *' {aka 'unsigned int *'}
   cc1: some warnings being treated as errors


vim +66 drivers/bluetooth/btintel.c

    49	
    50	static const guid_t btintel_guid_dsm =
    51		GUID_INIT(0xaa10f4e0, 0x81ac, 0x4233,
    52			  0xab, 0xf6, 0x3b, 0x2a, 0xc5, 0x0e, 0x28, 0xd9);
    53	
    54	static void *btintel_uefi_get_variable(efi_char16_t *name, efi_guid_t *guid)
    55	{
    56		void *data;
    57		efi_status_t status;
    58		size_t data_size = 0;
    59	
    60		if (!IS_ENABLED(CONFIG_EFI))
    61			return ERR_PTR(-EOPNOTSUPP);
    62	
    63		if (!efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE))
    64			return ERR_PTR(-EOPNOTSUPP);
    65	
  > 66		status = efi.get_variable(name, guid, NULL, &data_size, NULL);
    67	
    68		if (status != EFI_BUFFER_TOO_SMALL || !data_size)
    69			return ERR_PTR(-EIO);
    70	
    71		data = kmalloc(data_size, GFP_KERNEL);
    72	
    73		if (!data)
    74			return ERR_PTR(-ENOMEM);
    75	
    76		status = efi.get_variable(name, guid, NULL, &data_size, data);
    77	
    78		if (status != EFI_SUCCESS) {
    79			kfree(data);
    80			return ERR_PTR(-ENXIO);
    81		}
    82	
    83		return data;
    84	}
    85
kernel test robot June 26, 2024, 12:19 a.m. UTC | #4
Hi Kiran,

kernel test robot noticed the following build errors:

[auto build test ERROR on bluetooth-next/master]
[also build test ERROR on next-20240625]
[cannot apply to bluetooth/master linus/master v6.10-rc5]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Kiran-K/Bluetooth-btintel-Allow-lowering-of-drive-strength-of-BRI/20240625-161151
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth-next.git master
patch link:    https://lore.kernel.org/r/20240621064419.2185652-1-kiran.k%40intel.com
patch subject: [PATCH v2] Bluetooth: btintel: Allow lowering of drive strength of BRI
config: i386-buildonly-randconfig-001-20240626 (https://download.01.org/0day-ci/archive/20240626/202406260704.ZkFL5RKp-lkp@intel.com/config)
compiler: clang version 18.1.5 (https://github.com/llvm/llvm-project 617a15a9eac96088ae5e9134248d8236e34b91b1)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240626/202406260704.ZkFL5RKp-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202406260704.ZkFL5RKp-lkp@intel.com/

All errors (new ones prefixed by >>):

>> drivers/bluetooth/btintel.c:66:46: error: incompatible pointer types passing 'size_t *' (aka 'unsigned int *') to parameter of type 'unsigned long *' [-Werror,-Wincompatible-pointer-types]
      66 |         status = efi.get_variable(name, guid, NULL, &data_size, NULL);
         |                                                     ^~~~~~~~~~
   drivers/bluetooth/btintel.c:76:46: error: incompatible pointer types passing 'size_t *' (aka 'unsigned int *') to parameter of type 'unsigned long *' [-Werror,-Wincompatible-pointer-types]
      76 |         status = efi.get_variable(name, guid, NULL, &data_size, data);
         |                                                     ^~~~~~~~~~
   2 errors generated.


vim +66 drivers/bluetooth/btintel.c

    49	
    50	static const guid_t btintel_guid_dsm =
    51		GUID_INIT(0xaa10f4e0, 0x81ac, 0x4233,
    52			  0xab, 0xf6, 0x3b, 0x2a, 0xc5, 0x0e, 0x28, 0xd9);
    53	
    54	static void *btintel_uefi_get_variable(efi_char16_t *name, efi_guid_t *guid)
    55	{
    56		void *data;
    57		efi_status_t status;
    58		size_t data_size = 0;
    59	
    60		if (!IS_ENABLED(CONFIG_EFI))
    61			return ERR_PTR(-EOPNOTSUPP);
    62	
    63		if (!efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE))
    64			return ERR_PTR(-EOPNOTSUPP);
    65	
  > 66		status = efi.get_variable(name, guid, NULL, &data_size, NULL);
    67	
    68		if (status != EFI_BUFFER_TOO_SMALL || !data_size)
    69			return ERR_PTR(-EIO);
    70	
    71		data = kmalloc(data_size, GFP_KERNEL);
    72	
    73		if (!data)
    74			return ERR_PTR(-ENOMEM);
    75	
    76		status = efi.get_variable(name, guid, NULL, &data_size, data);
    77	
    78		if (status != EFI_SUCCESS) {
    79			kfree(data);
    80			return ERR_PTR(-ENXIO);
    81		}
    82	
    83		return data;
    84	}
    85
diff mbox series

Patch

diff --git a/drivers/bluetooth/btintel.c b/drivers/bluetooth/btintel.c
index 5d735391545a..3dc557aac43d 100644
--- a/drivers/bluetooth/btintel.c
+++ b/drivers/bluetooth/btintel.c
@@ -12,6 +12,8 @@ 
 #include <linux/acpi.h>
 #include <acpi/acpi_bus.h>
 #include <asm/unaligned.h>
+#include <linux/efi.h>
+
 
 #include <net/bluetooth/bluetooth.h>
 #include <net/bluetooth/hci_core.h>
@@ -49,6 +51,38 @@  static const guid_t btintel_guid_dsm =
 	GUID_INIT(0xaa10f4e0, 0x81ac, 0x4233,
 		  0xab, 0xf6, 0x3b, 0x2a, 0xc5, 0x0e, 0x28, 0xd9);
 
+static void *btintel_uefi_get_variable(efi_char16_t *name, efi_guid_t *guid)
+{
+	void *data;
+	efi_status_t status;
+	size_t data_size = 0;
+
+	if (!IS_ENABLED(CONFIG_EFI))
+		return ERR_PTR(-EOPNOTSUPP);
+
+	if (!efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE))
+		return ERR_PTR(-EOPNOTSUPP);
+
+	status = efi.get_variable(name, guid, NULL, &data_size, NULL);
+
+	if (status != EFI_BUFFER_TOO_SMALL || !data_size)
+		return ERR_PTR(-EIO);
+
+	data = kmalloc(data_size, GFP_KERNEL);
+
+	if (!data)
+		return ERR_PTR(-ENOMEM);
+
+	status = efi.get_variable(name, guid, NULL, &data_size, data);
+
+	if (status != EFI_SUCCESS) {
+		kfree(data);
+		return ERR_PTR(-ENXIO);
+	}
+
+	return data;
+}
+
 int btintel_check_bdaddr(struct hci_dev *hdev)
 {
 	struct hci_rp_read_bd_addr *bda;
@@ -2615,6 +2649,80 @@  static u8 btintel_classify_pkt_type(struct hci_dev *hdev, struct sk_buff *skb)
 	return hci_skb_pkt_type(skb);
 }
 
+static int btintel_set_dsbr(struct hci_dev *hdev, struct intel_version_tlv *ver)
+{
+	struct btintel_dsbr_cmd {
+		u8 enable;
+		u8 dsbr;
+	} __packed;
+
+	struct btintel_dsbr {
+		u8 header;
+		u32 dsbr;
+	} __packed;
+
+	struct btintel_dsbr *dsbr;
+	struct btintel_dsbr_cmd cmd;
+	struct sk_buff *skb;
+	u8 status;
+	efi_guid_t guid = EFI_GUID(0xe65d8884, 0xd4af, 0x4b20, 0x8d, 0x03,
+				   0x77, 0x2e, 0xcc, 0x3d, 0xa5, 0x31);
+
+	memset(&cmd, 0, sizeof(cmd));
+	dsbr = btintel_uefi_get_variable(L"UefiCnvCommonDSBR", &guid);
+	if (IS_ERR(dsbr)) {
+		/* If efi variable is not present, driver still needs to send
+		 * 0xfc0a command with default values
+		 */
+		bt_dev_dbg(hdev, "Error reading efi DSBR (%ld)",
+			   PTR_ERR(dsbr));
+		dsbr = NULL;
+	}
+
+	if (dsbr) {
+		/* bit0: 0 - Use firmware default value
+		 *       1 - Override firmware value
+		 * bit3:1 - Reserved
+		 * bit7:4 - DSBR override values
+		 * bt31:7 - Reserved
+		 */
+		cmd.enable = dsbr->dsbr & BIT(0);
+		if (cmd.enable)
+			cmd.dsbr = dsbr->dsbr >> 4 & 0xF;
+		kfree(dsbr);
+	}
+
+	bt_dev_info(hdev, "dsbr: enabled: 0x%2.2x value: 0x%2.2x", cmd.enable,
+		    cmd.dsbr);
+
+	skb = __hci_cmd_sync(hdev, 0xfc0a, sizeof(cmd), &cmd,  HCI_CMD_TIMEOUT);
+	if (IS_ERR(skb)) {
+		bt_dev_err(hdev, "Failed to send Intel DSBR command (%ld)",
+			   PTR_ERR(skb));
+		return -bt_to_errno(PTR_ERR(skb));
+	}
+
+	status = skb->data[0];
+	kfree_skb(skb);
+
+	if (status) {
+		bt_dev_err(hdev, "Set DSBR failed 0x%2.2x", status);
+		return -bt_to_errno(status);
+	}
+	return 0;
+}
+
+static int btintel_apply_dsbr(struct hci_dev *hdev,
+			      struct intel_version_tlv *ver)
+{
+	/* For BlazarI + B0 step, DSBR command needs to be sent just after
+	 * downloading IML firmware
+	 */
+	return ver->img_type == BTINTEL_IMG_IML &&
+		((ver->cnvi_top & 0xfff) == BTINTEL_CNVI_BLAZARI) &&
+		INTEL_CNVX_TOP_STEP(ver->cnvi_top) == 0x01;
+}
+
 int btintel_bootloader_setup_tlv(struct hci_dev *hdev,
 				 struct intel_version_tlv *ver)
 {
@@ -2649,6 +2757,12 @@  int btintel_bootloader_setup_tlv(struct hci_dev *hdev,
 	if (err)
 		return err;
 
+	if (btintel_apply_dsbr(hdev, ver)) {
+		err = btintel_set_dsbr(hdev, ver);
+		if (err)
+			return err;
+	}
+
 	/* If image type returned is BTINTEL_IMG_IML, then controller supports
 	 * intermediae loader image
 	 */