linux-kernel - Re: [PATCH] nand: ranw: qcom_nand: stop using phys_to

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Message-ID: <20180711150449.4152333c@bbrezillon>
Date:   Wed, 11 Jul 2018 15:04:49 +0200
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Miquel Raynal <miquel.raynal@...tlin.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Abhishek Sahu <absahu@...eaurora.org>,
        Archit Taneja <architt@...eaurora.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nand: ranw: qcom_nand: stop using phys_to_dma()

On Wed, 11 Jul 2018 14:26:58 +0200
Arnd Bergmann <arnd@...db.de> wrote:

> Compile-testing this driver on x86 caused a link error:
> 
> ERROR: "__phys_to_dma" [drivers/mtd/nand/raw/qcom_nandc.ko] undefined!
> 
> The problem here is that the driver attempts to convert the physical
> address into the DMA controller as a dma_addr_t and calls phys_to_dma()
> to do the conversion.
> 
> However, there is no generic way to convert a phys_addr_t into a dma_addr_t
> for anything other than RAM (which should use the dma-mapping API instead).
> The only correct use of phys_to_dma() instead is inside of the dma-mapping
> implementation.

Should we use dma_map_resource() to do the phys_addr_t to dma_addr_t
conversion?

> 
> In all other drivers that deal with DMA FIFO addresses, we just pass the
> physical address directly and have the DMA controller deal with that
> if necessary, so let's do the same thing here.
> 
> Fixes: c76b78d8ec05 ("mtd: nand: Qualcomm NAND controller driver")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/mtd/nand/raw/qcom_nandc.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/qcom_nandc.c b/drivers/mtd/nand/raw/qcom_nandc.c
> index 994f980c6d86..f047e2819041 100644
> --- a/drivers/mtd/nand/raw/qcom_nandc.c
> +++ b/drivers/mtd/nand/raw/qcom_nandc.c
> @@ -338,7 +338,6 @@ struct nandc_regs {
>   * @dev:			parent device
>   * @base:			MMIO base
>   * @base_phys:			physical base address of controller registers
> - * @base_dma:			dma base address of controller registers
>   * @core_clk:			controller clock
>   * @aon_clk:			another controller clock
>   *
> @@ -372,7 +371,6 @@ struct qcom_nand_controller {
>  
>  	void __iomem *base;
>  	phys_addr_t base_phys;
> -	dma_addr_t base_dma;
>  
>  	struct clk *core_clk;
>  	struct clk *aon_clk;
> @@ -935,11 +933,11 @@ static int prep_adm_dma_desc(struct qcom_nand_controller *nandc, bool read,
>  	slave_conf.device_fc = flow_control;
>  	if (read) {
>  		slave_conf.src_maxburst = 16;
> -		slave_conf.src_addr = nandc->base_dma + reg_off;
> +		slave_conf.src_addr = (dma_addr_t)nandc->base_phys + reg_off;
>  		slave_conf.slave_id = nandc->data_crci;
>  	} else {
>  		slave_conf.dst_maxburst = 16;
> -		slave_conf.dst_addr = nandc->base_dma + reg_off;
> +		slave_conf.dst_addr = (dma_addr_t)nandc->base_phys + reg_off;
>  		slave_conf.slave_id = nandc->cmd_crci;
>  	}
>  
> @@ -2963,7 +2961,6 @@ static int qcom_nandc_probe(struct platform_device *pdev)
>  		return PTR_ERR(nandc->base);
>  
>  	nandc->base_phys = res->start;
> -	nandc->base_dma = phys_to_dma(dev, (phys_addr_t)res->start);
>  
>  	nandc->core_clk = devm_clk_get(dev, "core");
>  	if (IS_ERR(nandc->core_clk))