linux-kernel - Re: [PATCH] mmc: sdhci-of-esdhc: set proper dma mask for ls104x chips

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Date:   Tue, 3 Jul 2018 11:15:13 +0000
From:   Laurentiu Tudor <laurentiu.tudor@....com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
CC:     Adrian Hunter <adrian.hunter@...el.com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Y.b. Lu" <yangbo.lu@....com>
Subject: Re: [PATCH] mmc: sdhci-of-esdhc: set proper dma mask for ls104x chips

Hi Uffe,

On 02.07.2018 17:37, Ulf Hansson wrote:
> On 28 June 2018 at 10:45, Laurentiu Tudor <laurentiu.tudor@....com> wrote:
>> SDHCI controller in ls1043a and ls1046a generate 40-bit wide addresses
>> when doing DMA. Make sure that the corresponding dma mask is correctly
>> configured.
>>
>> Signed-off-by: Laurentiu Tudor <laurentiu.tudor@....com>
> 
> Thanks, applied for next!

Thanks for picking this up!
I just realized that maybe I should have provided some context around 
this patch. I'm working on enabling smmu on these chips and encountered 
the following problem: the smmu input address size is 48 bits so the dma 
mappings for sdhci end up 48-bit wide. However, on these chips sdhci 
only use 40-bits of that address size when doing dma.
So you end up with a 48-bit address translation in smmu but the device 
generates transactions with clipped 40-bit addresses, thus smmu context 
faults are triggered. Setting up the correct dma mask fixes this situation.

---
Best Regards, Laurentiu

> 
>> ---
>>   drivers/mmc/host/sdhci-of-esdhc.c | 6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/drivers/mmc/host/sdhci-of-esdhc.c b/drivers/mmc/host/sdhci-of-esdhc.c
>> index 4ffa6b173a21..8332f56e6c0d 100644
>> --- a/drivers/mmc/host/sdhci-of-esdhc.c
>> +++ b/drivers/mmc/host/sdhci-of-esdhc.c
>> @@ -22,6 +22,7 @@
>>   #include <linux/sys_soc.h>
>>   #include <linux/clk.h>
>>   #include <linux/ktime.h>
>> +#include <linux/dma-mapping.h>
>>   #include <linux/mmc/host.h>
>>   #include "sdhci-pltfm.h"
>>   #include "sdhci-esdhc.h"
>> @@ -427,6 +428,11 @@ static void esdhc_of_adma_workaround(struct sdhci_host *host, u32 intmask)
>>   static int esdhc_of_enable_dma(struct sdhci_host *host)
>>   {
>>          u32 value;
>> +       struct device *dev = mmc_dev(host->mmc);
>> +
>> +       if (of_device_is_compatible(dev->of_node, "fsl,ls1043a-esdhc") ||
>> +           of_device_is_compatible(dev->of_node, "fsl,ls1046a-esdhc"))
>> +               dma_set_mask_and_coherent(dev, DMA_BIT_MASK(40));
>>
>>          value = sdhci_readl(host, ESDHC_DMA_SYSCTL);
>>          value |= ESDHC_DMA_SNOOP;
>> --
>> 2.17.1
>>