Re: [RFC PATCH 6/6] spi: Get rid of the spi_flash_read() API

[Boris Brezillon <boris.brezillon@bootlin.com>]

On Fri, 16 Feb 2018 15:51:00 +0530
Vignesh R <vigneshr@ti.com> wrote:

> Hi Boris,
> 
> On Tuesday 06 February 2018 04:51 AM, Boris Brezillon wrote:
> > From: Boris Brezillon <boris.brezillon@free-electrons.com>
> > 
> > This API has been replaced by the spi_mem_xx() one, its only user
> > (spi-nor) has been converted to spi_mem_xx() and all SPI controller
> > drivers that were implementing the ->spi_flash_xxx() hooks are also
> > implementing the spi_mem ones. So we can safely get rid of this API.
> > 
> > Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> > ---  
> 
> >  drivers/spi/spi-ti-qspi.c  | 41 ---------------------------------  
> 
> > -static bool ti_qspi_spi_flash_can_dma(struct spi_device *spi,
> > -				      struct spi_flash_read_message *msg)
> > -{
> > -	return virt_addr_valid(msg->buf);
> > -}
> > -  
> 
> 
> This causes kernel crash because spi_map_buf() now tries to map
> vmalloc'd buffers in LPAE backed memory not accessible by 32bit DMA:
> 
> ubiattach -p /dev/mtd9
> [  114.482439] Unable to handle kernel paging request at virtual address
> bf867000
> [  114.489689] pgd = 045b2870
> [  114.492403] [bf867000] *pgd=ad22c003, *pmd=00000000
> [  114.497309] Internal error: Oops: 2a06 [#1] PREEMPT SMP ARM
> [  114.502903] Modules linked in: ecdh_generic extcon_usb_gpio
> omap_aes_driver omap_sham omap_des des_generic crypto_engine omap_crypto
> [  114.514894] CPU: 1 PID: 1862 Comm: ubiattach Not tainted
> 4.16.0-rc1-next-20180212-00009-gbaa4bd31694e-dirty #16
> [  114.525023] Hardware name: Generic DRA74X (Flattened Device Tree)
> [  114.531145] PC is at v7_dma_inv_range+0x30/0x48
> [  114.535693] LR is at dma_cache_maint_page+0x110/0x124
> [  114.540763] pc : [<c0218fdc>]    lr : [<c02149e0>]    p
> 
> 
> We need ->can_dma like interface in spi_controller_mem_ops to prevent
> such buffers being mapped for certain SoCs. Or SPI NOR framework needs
> to use bounce buffers.
> 
> 

Actually, I'm doing the test directly in ti_qspi_exec_mem_op(), it's
just that my test is wrong :-):

		if (!virt_addr_valid(op->data.buf.in) &&
		    !spi_controller_dma_map_mem_op_data(mem->spi->master,
							op, &sgt)) {

should be

		if (virt_addr_valid(op->data.buf.in) &&
		    !spi_controller_dma_map_mem_op_data(mem->spi->master,
							op, &sgt)) {


-- 
Boris Brezillon, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
http://bootlin.com