linux-kernel - Re: [PATCH] mfd:rtsx: do retry when dma transfer error

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Message-ID: <20170103171727.GP2977@dell>
Date:   Tue, 3 Jan 2017 17:17:27 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     steven_feng@...lsil.com.cn
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mfd:rtsx: do retry when dma transfer error

On Fri, 09 Dec 2016, steven_feng@...lsil.com.cn wrote:

> From: steven_feng <steven_feng@...lsil.com.cn>
> 
> the request should be reissued when dma transfer error.
> for rts5227, the clock freq need to step reduce when error occurred.
> 
> Signed-off-by: steven_feng <steven_feng@...lsil.com.cn>
> ---
>  drivers/mfd/rtsx_pcr.c       | 15 +++++++++++++--
>  include/linux/mfd/rtsx_pci.h |  2 ++
>  2 files changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mfd/rtsx_pcr.c b/drivers/mfd/rtsx_pcr.c
> index 98029ee..1684e61 100644
> --- a/drivers/mfd/rtsx_pcr.c
> +++ b/drivers/mfd/rtsx_pcr.c
> @@ -30,6 +30,7 @@
>  #include <linux/platform_device.h>
>  #include <linux/mfd/core.h>
>  #include <linux/mfd/rtsx_pci.h>
> +#include <linux/mmc/card.h>
>  #include <asm/unaligned.h>
>  
>  #include "rtsx_pcr.h"
> @@ -452,8 +453,12 @@ int rtsx_pci_dma_transfer(struct rtsx_pcr *pcr, struct scatterlist *sglist,
>  	}
>  
>  	spin_lock_irqsave(&pcr->lock, flags);
> -	if (pcr->trans_result == TRANS_RESULT_FAIL)
> -		err = -EINVAL;
> +	if (pcr->trans_result == TRANS_RESULT_FAIL) {
> +		err = -EILSEQ;

This seems strange.  What is the reason for using this error?

> +		if (pcr->dma_error_count < 8)

Why 8?

> +			pcr->dma_error_count++;
> +	}
> +
>  	else if (pcr->trans_result == TRANS_NO_DEVICE)
>  		err = -ENODEV;
>  	spin_unlock_irqrestore(&pcr->lock, flags);
> @@ -659,6 +664,11 @@ int rtsx_pci_switch_clock(struct rtsx_pcr *pcr, unsigned int card_clock,
>  	if (err < 0)
>  		return err;
>  
> +	if (card_clock == UHS_SDR104_MAX_DTR &&
> +			pcr->dma_error_count && PCI_PID(pcr) == 0x5227)

Tabbing is off here.

What does 0x5227 mean?  No magic numbers.  Please define it.

> +		card_clock = UHS_SDR104_MAX_DTR -
> +			pcr->dma_error_count * 20000000;

What does this do?

Looks like you need a comment to describe what you're trying to
achieve.

>  	card_clock /= 1000000;
>  	pcr_dbg(pcr, "Switch card clock to %dMHz\n", card_clock);
>  
> @@ -894,6 +904,7 @@ static irqreturn_t rtsx_pci_isr(int irq, void *dev_id)
>  			pcr->card_removed |= SD_EXIST;
>  			pcr->card_inserted &= ~SD_EXIST;
>  		}
> +		pcr->dma_error_count = 0;
>  	}
>  
>  	if (int_reg & MS_INT) {
> diff --git a/include/linux/mfd/rtsx_pci.h b/include/linux/mfd/rtsx_pci.h
> index 7eb7cba..1d65f4e 100644
> --- a/include/linux/mfd/rtsx_pci.h
> +++ b/include/linux/mfd/rtsx_pci.h
> @@ -957,6 +957,8 @@ struct rtsx_pcr {
>  
>  	int				num_slots;
>  	struct rtsx_slot		*slots;
> +
> +	u8				dma_error_count;
>  };
>  
>  #define CHK_PCI_PID(pcr, pid)		((pcr)->pci->device == (pid))

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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