Re: [PATCH v2 2/2] memory: ti-k3-fsas: Add TI FSS_FSAS driver

[Krzysztof Kozlowski <krzk@kernel.org>]

On 29/06/2026 09:20, Santhosh Kumar K wrote:
> Add a platform driver for the TI Flash SubSystem Application Subsystem
> (FSS_FSAS_GENREGS) in K3 SoCs. This driver takes care of disabling the
> OSPI XIP prefetch which causes DMA transfer data corruption.
> 
> Set SYSCONFIG.DISXIP to disable XIP read prefetch, preventing DMA data
> corruption when the OSPI DMA source address is not 4K-aligned.
> 
> Signed-off-by: Santhosh Kumar K <s-k6@ti.com>
> ---
>  drivers/memory/Kconfig      | 10 +++++
>  drivers/memory/Makefile     |  1 +
>  drivers/memory/ti-k3-fsas.c | 74 +++++++++++++++++++++++++++++++++++++
>  3 files changed, 85 insertions(+)
>  create mode 100644 drivers/memory/ti-k3-fsas.c
> 
> diff --git a/drivers/memory/Kconfig b/drivers/memory/Kconfig
> index e5527020ff33..954e47810e8d 100644
> --- a/drivers/memory/Kconfig
> +++ b/drivers/memory/Kconfig
> @@ -125,6 +125,16 @@ config TI_EMIF_SRAM
>  	  sequence so this driver provides several relocatable PM functions
>  	  for the SoC PM code to use.
>  
> +config TI_K3_FSS_FSAS
> +	tristate "TI K3 Flash Subsystem Application Subsystem (FSAS) support"
> +	depends on ARCH_K3 || COMPILE_TEST
> +	help
> +	  Driver for the TI K3 Flash Subsystem Application Subsystem
> +	  (FSS_FSAS_GENREGS) wrapper found on K3 related SoCs.
> +
> +	  This driver takes care of disabling the OSPI XIP prefetch which
> +	  causes DMA transfer data corruption.
> +
>  config FPGA_DFL_EMIF
>  	tristate "FPGA DFL EMIF Driver"
>  	depends on FPGA_DFL && HAS_IOMEM
> diff --git a/drivers/memory/Makefile b/drivers/memory/Makefile
> index 3ee883c8759a..8dc4860f615d 100644
> --- a/drivers/memory/Makefile
> +++ b/drivers/memory/Makefile
> @@ -28,6 +28,7 @@ obj-$(CONFIG_STM32_OMM)		+= stm32_omm.o
>  obj-$(CONFIG_SAMSUNG_MC)	+= samsung/
>  obj-$(CONFIG_TEGRA_MC)		+= tegra/
>  obj-$(CONFIG_TI_EMIF_SRAM)	+= ti-emif-sram.o
> +obj-$(CONFIG_TI_K3_FSS_FSAS)	+= ti-k3-fsas.o
>  obj-$(CONFIG_FPGA_DFL_EMIF)	+= dfl-emif.o
>  
>  ti-emif-sram-objs		:= ti-emif-pm.o ti-emif-sram-pm.o
> diff --git a/drivers/memory/ti-k3-fsas.c b/drivers/memory/ti-k3-fsas.c
> new file mode 100644
> index 000000000000..a5f42afc694c
> --- /dev/null
> +++ b/drivers/memory/ti-k3-fsas.c
> @@ -0,0 +1,74 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * TI K3 Flash Subsystem Application Subsystem (FSS_FSAS) driver
> + *
> + * Copyright (C) 2025 Texas Instruments Incorporated - https://www.ti.com
> + */
> +
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm.h>
> +
> +#define FSAS_GENREGS_SYSCONFIG 0x04
> +#define FSAS_SYSCONFIG_DISXIP BIT(7)
> +
> +struct k3_fsas {
> +	void __iomem *base;
> +};
> +
> +static void k3_fsas_disable_xip_prefetch(struct k3_fsas *fsas)
> +{
> +	u32 val;
> +
> +	val = readl(fsas->base + FSAS_GENREGS_SYSCONFIG);
> +	val |= FSAS_SYSCONFIG_DISXIP;
> +	writel(val, fsas->base + FSAS_GENREGS_SYSCONFIG);
> +}
> +
> +static int k3_fsas_probe(struct platform_device *pdev)
> +{
> +	struct k3_fsas *fsas;
> +
> +	fsas = devm_kzalloc(&pdev->dev, sizeof(*fsas), GFP_KERNEL);
> +	if (!fsas)
> +		return -ENOMEM;
> +
> +	fsas->base = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(fsas->base))
> +		return PTR_ERR(fsas->base);
> +
> +	platform_set_drvdata(pdev, fsas);
> +
> +	k3_fsas_disable_xip_prefetch(fsas);

So a driver for FSAS device just writes to one register. That's why I
claim binding is either incomplete or not really a separate device.

Plus how does this work when you probe QSPI before this FSAS?

Best regards,
Krzysztof