Re: [PATCH v4 2/9] bus: mhi: Move sahara protocol driver under drivers/bus/mhi

[Manivannan Sadhasivam]

On Thu, Mar 19, 2026 at 12:01:42PM +0530, Kishore Batta wrote:
> The Sahara protocol driver is currently located under the QAIC
> accelerator subsystem even though protocol itself is transported over the
> MHI bus and is used by multiple Qualcomm flashless devices.
> 
> Relocate the Sahara protocol driver to drivers/bus/mhi and register it as
> an independent MHI protocol driver. This avoids treating Sahara as QAIC
> specific and makes it available for reuse by other MHI based devices.
> 
> As part of this move, introduce a dedicated Kconfig and Makefile under the
> MHI subsystem and expose the sahara interface via a common header.
> 
> Signed-off-by: Kishore Batta <kishore.batta@xxxxxxxxxxxxxxxx>
> ---
>  drivers/accel/qaic/Kconfig                      |  1 +
>  drivers/accel/qaic/Makefile                     |  3 +--
>  drivers/accel/qaic/qaic_drv.c                   | 11 ++---------
>  drivers/bus/mhi/Kconfig                         |  1 +
>  drivers/bus/mhi/Makefile                        |  3 +++
>  drivers/bus/mhi/sahara/Kconfig                  | 18 ++++++++++++++++++
>  drivers/bus/mhi/sahara/Makefile                 |  2 ++

Create one more subidr 'clients' and move 'sahara' here:
	drivers/bus/mhi/host/clients/sahara/

I'm not sure if we are going to have Sahara implementation for the endpoint
itself. If so, it should be moved under drivers/bus/mhi/common/.

>  drivers/{accel/qaic => bus/mhi/sahara}/sahara.c | 16 +++++++++++-----
>  {drivers/accel/qaic => include/linux}/sahara.h  |  0

include/linux/mhi/sahara.h

>  9 files changed, 39 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/accel/qaic/Kconfig b/drivers/accel/qaic/Kconfig
> index 116e42d152ca885b8c59e33c7a87519a0abc6bb3..1e5f1f4fa93c12d8ca8fb37633f2f0bee9997499 100644
> --- a/drivers/accel/qaic/Kconfig
> +++ b/drivers/accel/qaic/Kconfig
> @@ -8,6 +8,7 @@ config DRM_ACCEL_QAIC
>  	depends on DRM_ACCEL
>  	depends on PCI && HAS_IOMEM
>  	depends on MHI_BUS
> +	select MHI_SAHARA
>  	select CRC32
>  	select WANT_DEV_COREDUMP
>  	help
> diff --git a/drivers/accel/qaic/Makefile b/drivers/accel/qaic/Makefile
> index 71f727b74da3bb4478324689f02a7cea24a05c2d..e7b8458800072aa627f7f36c3257883aa56f4ce4 100644
> --- a/drivers/accel/qaic/Makefile
> +++ b/drivers/accel/qaic/Makefile
> @@ -13,7 +13,6 @@ qaic-y := \
>  	qaic_ras.o \
>  	qaic_ssr.o \
>  	qaic_sysfs.o \
> -	qaic_timesync.o \
> -	sahara.o
> +	qaic_timesync.o
>  
>  qaic-$(CONFIG_DEBUG_FS) += qaic_debugfs.o
> diff --git a/drivers/accel/qaic/qaic_drv.c b/drivers/accel/qaic/qaic_drv.c
> index 63fb8c7b4abcbe4f1b76c32106f4e8b9ea5e2c8e..76cc8086825e7949ed756d51fcb56a08f392d228 100644
> --- a/drivers/accel/qaic/qaic_drv.c
> +++ b/drivers/accel/qaic/qaic_drv.c
> @@ -15,6 +15,7 @@
>  #include <linux/msi.h>
>  #include <linux/mutex.h>
>  #include <linux/pci.h>
> +#include <linux/sahara.h>
>  #include <linux/spinlock.h>
>  #include <linux/workqueue.h>
>  #include <linux/wait.h>
> @@ -32,7 +33,6 @@
>  #include "qaic_ras.h"
>  #include "qaic_ssr.h"
>  #include "qaic_timesync.h"
> -#include "sahara.h"
>  
>  MODULE_IMPORT_NS("DMA_BUF");
>  
> @@ -782,18 +782,12 @@ static int __init qaic_init(void)
>  	ret = pci_register_driver(&qaic_pci_driver);
>  	if (ret) {
>  		pr_debug("qaic: pci_register_driver failed %d\n", ret);
> -		return ret;
> +		goto free_pci;
>  	}
>  
>  	ret = mhi_driver_register(&qaic_mhi_driver);
>  	if (ret) {
>  		pr_debug("qaic: mhi_driver_register failed %d\n", ret);
> -		goto free_pci;
> -	}
> -
> -	ret = sahara_register();
> -	if (ret) {
> -		pr_debug("qaic: sahara_register failed %d\n", ret);
>  		goto free_mhi;
>  	}
>  
> @@ -847,7 +841,6 @@ static void __exit qaic_exit(void)
>  	qaic_ras_unregister();
>  	qaic_bootlog_unregister();
>  	qaic_timesync_deinit();
> -	sahara_unregister();
>  	mhi_driver_unregister(&qaic_mhi_driver);
>  	pci_unregister_driver(&qaic_pci_driver);
>  }
> diff --git a/drivers/bus/mhi/Kconfig b/drivers/bus/mhi/Kconfig
> index b39a11e6c624ba00349cca22d74bd876020590ab..4acedb886adccc6f76f69c241d53106da59b491f 100644
> --- a/drivers/bus/mhi/Kconfig
> +++ b/drivers/bus/mhi/Kconfig
> @@ -7,3 +7,4 @@
>  
>  source "drivers/bus/mhi/host/Kconfig"
>  source "drivers/bus/mhi/ep/Kconfig"
> +source "drivers/bus/mhi/sahara/Kconfig"
> diff --git a/drivers/bus/mhi/Makefile b/drivers/bus/mhi/Makefile
> index 354204b0ef3ae4030469a24a659f32429d592aef..e4af535e1bb1bc9481fae60d7eb347700d2e874c 100644
> --- a/drivers/bus/mhi/Makefile
> +++ b/drivers/bus/mhi/Makefile
> @@ -3,3 +3,6 @@ obj-$(CONFIG_MHI_BUS) += host/
>  
>  # Endpoint MHI stack
>  obj-$(CONFIG_MHI_BUS_EP) += ep/
> +
> +# Sahara MHI protocol
> +obj-$(CONFIG_MHI_SAHARA) += sahara/
> diff --git a/drivers/bus/mhi/sahara/Kconfig b/drivers/bus/mhi/sahara/Kconfig
> new file mode 100644
> index 0000000000000000000000000000000000000000..3f1caf6acd979a4af68aaf0e250aa54762e8cda5
> --- /dev/null
> +++ b/drivers/bus/mhi/sahara/Kconfig
> @@ -0,0 +1,18 @@
> +config MHI_SAHARA
> +	tristate
> +	depends on MHI_BUS
> +	select FW_LOADER_COMPRESS
> +	select FW_LOADER_COMPRESS_XZ
> +	select FW_LOADER_COMPRESS_ZSTD

Why suddenly these configs pop up?

> +	help
> +	  Enable support for the Sahara protocol transported over the MHI bus.
> +
> +	  The Sahara protocol is used to transfer firmware images, retrieve
> +	  memory dumps and exchange command mode DDR calibration data between
> +	  host and device. This driver is not tied to a specific SoC and may be
> +	  used by multiple MHI based devices.
> +
> +	  If unsure, say N.
> +
> +	  To compile this driver as a module, choose M here: the module will be
> +	  called mhi_sahara.
> diff --git a/drivers/bus/mhi/sahara/Makefile b/drivers/bus/mhi/sahara/Makefile
> new file mode 100644
> index 0000000000000000000000000000000000000000..fc02a25935011cbd7138ea8f24b88cf5b032a4ce
> --- /dev/null
> +++ b/drivers/bus/mhi/sahara/Makefile
> @@ -0,0 +1,2 @@
> +obj-$(CONFIG_MHI_SAHARA) += mhi_sahara.o
> +mhi_sahara-y := sahara.o
> diff --git a/drivers/accel/qaic/sahara.c b/drivers/bus/mhi/sahara/sahara.c
> similarity index 99%
> rename from drivers/accel/qaic/sahara.c
> rename to drivers/bus/mhi/sahara/sahara.c
> index fd3c3b2d1fd3bb698809e6ca669128e2dce06613..8ff7b6425ac5423ef8f32117151dca10397686a8 100644
> --- a/drivers/accel/qaic/sahara.c
> +++ b/drivers/bus/mhi/sahara/sahara.c
> @@ -1,6 +1,8 @@
> -// SPDX-License-Identifier: GPL-2.0-only
> -
> -/* Copyright (c) 2024 Qualcomm Innovation Center, Inc. All rights reserved. */
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2018-2020, The Linux Foundation. All rights reserved.

Why are you changing the copyright?

> + *
> + */
>  
>  #include <linux/devcoredump.h>
>  #include <linux/firmware.h>
> @@ -9,12 +11,11 @@
>  #include <linux/minmax.h>
>  #include <linux/mod_devicetable.h>
>  #include <linux/overflow.h>
> +#include <linux/sahara.h>
>  #include <linux/types.h>
>  #include <linux/vmalloc.h>
>  #include <linux/workqueue.h>
>  
> -#include "sahara.h"
> -
>  #define SAHARA_HELLO_CMD		0x1  /* Min protocol version 1.0 */
>  #define SAHARA_HELLO_RESP_CMD		0x2  /* Min protocol version 1.0 */
>  #define SAHARA_READ_DATA_CMD		0x3  /* Min protocol version 1.0 */
> @@ -928,8 +929,13 @@ int sahara_register(void)
>  {
>  	return mhi_driver_register(&sahara_mhi_driver);
>  }
> +module_init(sahara_register);
>  
>  void sahara_unregister(void)
>  {
>  	mhi_driver_unregister(&sahara_mhi_driver);
>  }
> +module_exit(sahara_unregister);

Use module_mhi_driver().

- Mani

-- 
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