Linux/AM3352: GPMC access from kernel

yingjie gu

Part Number: AM3352

Tool/software: Linux

Hi,

I am using sdk 3.3.0.4. I have a FPGA connected to GPMC and am writing a kernel driver to deal with interrupts from FPGA.

In user space, I use mmap to access FPGA, starting from offset 0x01000000.

In kernel, the driver needs to write 0 to some bits in FPGA to clear the interrupt in IRQ Handler.

Can anybody tell me how can I access the GPMC FPGA in kernel?

Thanks .

over 7 years ago

0 Biser Gatchev-XID over 7 years ago

TI__Guru**** 393215 points

GPMC is memory mapped. You simply write to the memory address you need.

0 yingjie gu over 7 years ago in reply to Biser Gatchev-XID

Intellectual 810 points

Thank you for replying.
You mean like this?
In kernel driver:
# define FPGA_BASE 0X01000000
struct interrupt_struct *irq=FPGA_BASE+irq_offset;
irq->set=0xf;

Is this the case for GPIO too?

0 Pavel Botev over 7 years ago in reply to yingjie gu

TI__Guru**** 170625 points

yingjie gu said:
In kernel driver:
# define FPGA_BASE 0X01000000
struct interrupt_struct *irq=FPGA_BASE+irq_offset;
irq->set=0xf;

I would suggest you to try with writel_relaxed() or __raw_writel() functions. See for example GPMC driver:

linux-kernel/drivers/memory/omap-gpmc.c

This driver is using writel_relaxed() to write into GPMC registers. GPMC registers are located at: 0x50000000 to 0x50FFFFFF (16MB). You can re-use that approach to write into GPMC memory: 0x01000000 to 0x1FFFFFFF (512MB).

yingjie gu said:
Is this the case for GPIO too?

GPIO has no memory area (as GPMC has), GPIO has only registers area. And GPIO driver is using also writel_relaxed() to write into GPIO registers.

linux-kernel/drivers/gpio/gpio-omap.c

Regards,
Pavel

0 Pavel Botev over 7 years ago in reply to Pavel Botev

TI__Guru**** 170625 points

Check also below e2e thread:

e2e.ti.com/.../455417

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Linux/AM3352: GPMC access from kernel