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

Boris Brezillon
2018-02-16T10:25:10Z

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 This API has been replaced by the spi_mem_xx() one, its only user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