linux-kernel - Re: [PATCH v4] mfd:rtsx: do retry when DMA transfer error

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Message-ID: <20170522101458.6eoywhgjrboeuy4k@dell>
Date:   Mon, 22 May 2017 11:14:58 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     steven_feng@...lsil.com.cn
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] mfd:rtsx: do retry when DMA transfer error

On Wed, 26 Apr 2017, steven_feng@...lsil.com.cn wrote:

> From: Steven Feng <steven_feng@...lsil.com.cn>
> 
> The request should be resent when DMA transfer error occurred.
> For rts5227, the clock rate needs to be reduced when error occurred.
> 
> Signed-off-by: Steven Feng <steven_feng@...lsil.com.cn>
> ---
>  drivers/mfd/rtsx_pcr.c       | 18 ++++++++++++++++--
>  include/linux/mfd/rtsx_pci.h |  5 +++++
>  2 files changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mfd/rtsx_pcr.c b/drivers/mfd/rtsx_pcr.c
> index 98029ee..8e21fd6 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;
> +		if (pcr->dma_error_count < RTS_MAX_TIMES_FREQ_REDUCTION)
> +			pcr->dma_error_count++;
> +	}
> +
>  	else if (pcr->trans_result == TRANS_NO_DEVICE)
>  		err = -ENODEV;
>  	spin_unlock_irqrestore(&pcr->lock, flags);
> @@ -659,6 +664,14 @@ int rtsx_pci_switch_clock(struct rtsx_pcr *pcr, unsigned int card_clock,
>  	if (err < 0)
>  		return err;
>  
> +	/* Reduce MMC card clock by 20MHz each time a DMA transfer error occurs
> +	 */

This is not a correctly formatted multi-line comment in the kernel.

Reword and make it a single line comment.

> +	if (card_clock == UHS_SDR104_MAX_DTR &&
> +		pcr->dma_error_count &&
> +		PCI_PID(pcr) == RTS5227_DEVICE_ID)

It would be nicer if these aligned after the '('.

> +		card_clock = UHS_SDR104_MAX_DTR -
> +			(pcr->dma_error_count * 20000000);
>  
>  	card_clock /= 1000000;
>  	pcr_dbg(pcr, "Switch card clock to %dMHz\n", card_clock);
>  
> @@ -894,6 +907,7 @@ 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..116816f 100644
> --- a/include/linux/mfd/rtsx_pci.h
> +++ b/include/linux/mfd/rtsx_pci.h
> @@ -850,6 +850,9 @@
>  
>  #define rtsx_pci_init_cmd(pcr)		((pcr)->ci = 0)
>  
> +#define RTS5227_DEVICE_ID		0x5227
> +#define RTS_MAX_TIMES_FREQ_REDUCTION	8
> +
>  struct rtsx_pcr;
>  
>  struct pcr_handle {
> @@ -957,6 +960,8 @@ 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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