[PATCH] Disable write buffering on Toshiba ToPIC95

[Dominik Brodowski]

Ryan,

thanks for this patch. Could you add a "Signed-off-by" line as specified in
Documentation/SubmittingPatches, please, so that I can pick it up and push
it upstream? Thanks!

	Dominik

On Sun, Jan 25, 2015 at 04:07:09PM -0800, Ryan C. Underwood wrote:
> From: Ryan Underwood <nemesis at icequake.net>
> 
> Disable write buffering on the Toshiba ToPIC95 if it is enabled by somebody (it
> is not supposed to be a power-on default according to the datasheet).  On the
> ToPIC95, practically no 32-bit Cardbus card will work under heavy load without
> locking up the whole system if this is left enabled.  I tried about a dozen.
> It does not affect 16-bit cards.  This is similar to the O2 bugs in early
> controller revisions it seems.  Originally posted to
> https://bugzilla.kernel.org/show_bug.cgi?id=55961
> ---
>  drivers/pcmcia/topic.h | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/pcmcia/topic.h b/drivers/pcmcia/topic.h
> index 615a45a..582688fe 100644
> --- a/drivers/pcmcia/topic.h
> +++ b/drivers/pcmcia/topic.h
> @@ -104,6 +104,9 @@
>  #define TOPIC_EXCA_IF_CONTROL		0x3e	/* 8 bit */
>  #define TOPIC_EXCA_IFC_33V_ENA		0x01
>  
> +#define TOPIC_PCI_CFG_PPBCN		0x3e	/* 16-bit */
> +#define TOPIC_PCI_CFG_PPBCN_WBEN	0x0400
> +
>  static void topic97_zoom_video(struct pcmcia_socket *sock, int onoff)
>  {
>  	struct yenta_socket *socket = container_of(sock, struct yenta_socket, socket);
> @@ -138,6 +141,7 @@ static int topic97_override(struct yenta_socket *socket)
>  static int topic95_override(struct yenta_socket *socket)
>  {
>  	u8 fctrl;
> +	u16 ppbcn;
>  
>  	/* enable 3.3V support for 16bit cards */
>  	fctrl = exca_readb(socket, TOPIC_EXCA_IF_CONTROL);
> @@ -146,6 +150,18 @@ static int topic95_override(struct yenta_socket *socket)
>  	/* tell yenta to use exca registers to power 16bit cards */
>  	socket->flags |= YENTA_16BIT_POWER_EXCA | YENTA_16BIT_POWER_DF;
>  
> +	/* Disable write buffers to prevent lockups under load with numerous
> +	   Cardbus cards, observed on Tecra 500CDT and reported elsewhere on the
> +	   net.  This is not a power-on default according to the datasheet
> +	   but some BIOSes seem to set it. */
> +	if (pci_read_config_word(socket->dev, TOPIC_PCI_CFG_PPBCN, &ppbcn) == 0
> +	    && socket->dev->revision <= 7
> +	    && (ppbcn & TOPIC_PCI_CFG_PPBCN_WBEN)) {
> +		ppbcn &= ~TOPIC_PCI_CFG_PPBCN_WBEN;
> +		pci_write_config_word(socket->dev, TOPIC_PCI_CFG_PPBCN, ppbcn);
> +		dev_info(&socket->dev->dev, "Disabled ToPIC95 Cardbus write buffers.\n");
> +	}
> +
>  	return 0;
>  }
>  
> -- 
> 1.9.1
> 
> --
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