linux-kernel - Re: [PATCH] mmc: tegra: Implement enable_dma() to set dma

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Message-ID: <20190813093651.GE1137@ulmo>
Date:   Tue, 13 Aug 2019 11:36:51 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Nicolin Chen <nicoleotsuka@...il.com>
Cc:     adrian.hunter@...el.com, ulf.hansson@...aro.org,
        jonathanh@...dia.com, linux-mmc@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        vdumpa@...dia.com
Subject: Re: [PATCH] mmc: tegra: Implement enable_dma() to set dma_mask

On Mon, Aug 12, 2019 at 03:42:17PM -0700, Nicolin Chen wrote:
> Commit 68481a7e1c84 ("mmc: tegra: Mark 64 bit dma broken on Tegra186")
> added a SDHCI_QUIRK2_BROKEN_64_BIT_DMA flag to let sdhci core fallback
> to 32-bit DMA so as to fit the 40-bit addressing on Tegra186. However,
> there's a common way, being mentioned in sdhci.c file, to set dma_mask
> via enable_dma() callback in the device driver directly.
> 
> So this patch implements an enable_dma() callback in the sdhci-tegra,
> in order to set an accurate DMA_BIT_MASK, other than 32-bit or 64-bit.
> 
> Signed-off-by: Nicolin Chen <nicoleotsuka@...il.com>
> ---
>  drivers/mmc/host/sdhci-tegra.c | 28 +++++++++++++++++++---------
>  1 file changed, 19 insertions(+), 9 deletions(-)

I like this. However, I'd prefer if we set the DMA mask explicitly for
each generation. A while ago, I had done a similar patch which relied on
some core changes that no longer seem necessary with this enable_dma()
hook. You can find the DMA masks for each generation in that patch:

	http://patchwork.ozlabs.org/patch/1020678/

Thierry

> diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
> index f4d4761cf20a..23289adb78d6 100644
> --- a/drivers/mmc/host/sdhci-tegra.c
> +++ b/drivers/mmc/host/sdhci-tegra.c
> @@ -16,6 +16,7 @@
>  #include <linux/pinctrl/consumer.h>
>  #include <linux/regulator/consumer.h>
>  #include <linux/reset.h>
> +#include <linux/dma-mapping.h>
>  #include <linux/mmc/card.h>
>  #include <linux/mmc/host.h>
>  #include <linux/mmc/mmc.h>
> @@ -104,6 +105,7 @@
>  
>  struct sdhci_tegra_soc_data {
>  	const struct sdhci_pltfm_data *pdata;
> +	u64 dma_bit_mask;
>  	u32 nvquirks;
>  	u8 min_tap_delay;
>  	u8 max_tap_delay;
> @@ -749,6 +751,19 @@ static void tegra_sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
>  	}
>  }
>  
> +static int tegra_sdhci_enable_dma(struct sdhci_host *host)
> +{
> +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> +	struct sdhci_tegra *tegra_host = sdhci_pltfm_priv(pltfm_host);
> +	const struct sdhci_tegra_soc_data *soc_data = tegra_host->soc_data;
> +	struct device *dev = mmc_dev(host->mmc);
> +
> +	if (soc_data->dma_bit_mask)
> +		return dma_set_mask_and_coherent(dev, soc_data->dma_bit_mask);
> +
> +	return 0;
> +}
> +
>  static unsigned int tegra_sdhci_get_max_clock(struct sdhci_host *host)
>  {
>  	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> @@ -1370,6 +1385,7 @@ static const struct sdhci_ops tegra186_sdhci_ops = {
>  	.write_l    = tegra_sdhci_writel,
>  	.set_clock  = tegra_sdhci_set_clock,
>  	.set_bus_width = sdhci_set_bus_width,
> +	.enable_dma = tegra_sdhci_enable_dma,
>  	.reset      = tegra_sdhci_reset,
>  	.set_uhs_signaling = tegra_sdhci_set_uhs_signaling,
>  	.voltage_switch = tegra_sdhci_voltage_switch,
> @@ -1384,20 +1400,13 @@ static const struct sdhci_pltfm_data sdhci_tegra186_pdata = {
>  		  SDHCI_QUIRK_NO_HISPD_BIT |
>  		  SDHCI_QUIRK_BROKEN_ADMA_ZEROLEN_DESC |
>  		  SDHCI_QUIRK_CAP_CLOCK_BASE_BROKEN,
> -	.quirks2 = SDHCI_QUIRK2_PRESET_VALUE_BROKEN |
> -		   /* SDHCI controllers on Tegra186 support 40-bit addressing.
> -		    * IOVA addresses are 48-bit wide on Tegra186.
> -		    * With 64-bit dma mask used for SDHCI, accesses can
> -		    * be broken. Disable 64-bit dma, which would fall back
> -		    * to 32-bit dma mask. Ideally 40-bit dma mask would work,
> -		    * But it is not supported as of now.
> -		    */
> -		   SDHCI_QUIRK2_BROKEN_64_BIT_DMA,
> +	.quirks2 = SDHCI_QUIRK2_PRESET_VALUE_BROKEN,
>  	.ops  = &tegra186_sdhci_ops,
>  };
>  
>  static const struct sdhci_tegra_soc_data soc_data_tegra186 = {
>  	.pdata = &sdhci_tegra186_pdata,
> +	.dma_bit_mask = DMA_BIT_MASK(40),
>  	.nvquirks = NVQUIRK_NEEDS_PAD_CONTROL |
>  		    NVQUIRK_HAS_PADCALIB |
>  		    NVQUIRK_DIS_CARD_CLK_CONFIG_TAP |
> @@ -1410,6 +1419,7 @@ static const struct sdhci_tegra_soc_data soc_data_tegra186 = {
>  
>  static const struct sdhci_tegra_soc_data soc_data_tegra194 = {
>  	.pdata = &sdhci_tegra186_pdata,
> +	.dma_bit_mask = DMA_BIT_MASK(39),
>  	.nvquirks = NVQUIRK_NEEDS_PAD_CONTROL |
>  		    NVQUIRK_HAS_PADCALIB |
>  		    NVQUIRK_DIS_CARD_CLK_CONFIG_TAP |
> -- 
> 2.17.1
> 

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