From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ulf Hansson Subject: Re: [PATCH] mmc: core: Lower max_seg_size if too high for DMA Date: Thu, 29 Nov 2018 21:11:17 +0100 Message-ID: References: <20181031155738.18367-1-tony@atomide.com> <20181129191332.GY53235@atomide.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20181129191332.GY53235@atomide.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Tony Lindgren Cc: "linux-mmc@vger.kernel.org" , Kishon , Peter Ujfalusi , Russell King , linux-omap , Linux ARM List-Id: linux-mmc@vger.kernel.org On Thu, 29 Nov 2018 at 20:13, Tony Lindgren wrote: > > * Ulf Hansson [181119 12:09]: > > On 31 October 2018 at 16:57, Tony Lindgren wrote: > > > With CONFIG_DMA_API_DEBUG_SG a device may produce the following warning: > > > > > > "DMA-API: mapping sg segment longer than device claims to support" > > > > > > We default to 64KiB if a DMA engine driver does not initialize dma_parms > > > and call dma_set_max_seg_size(). This may be lower that what many MMC > > > drivers do with mmc->max_seg_size = mmc->max_blk_size * mmc->max_blk_count. > > > > > > Let's do a sanity check for max_seg_size being higher than what DMA > > > supports in mmc_add_host() and lower it as needed. > > > > > > Cc: Kishon Vijay Abraham I > > > Cc: Peter Ujfalusi > > > Cc: Russell King > > > Reported-by: Russell King > > > Signed-off-by: Tony Lindgren > > > --- > > > drivers/mmc/core/host.c | 16 ++++++++++++++++ > > > 1 file changed, 16 insertions(+) > > > > > > diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c > > > --- a/drivers/mmc/core/host.c > > > +++ b/drivers/mmc/core/host.c > > > @@ -13,6 +13,7 @@ > > > */ > > > > > > #include > > > +#include > > > #include > > > #include > > > #include > > > @@ -415,6 +416,19 @@ struct mmc_host *mmc_alloc_host(int extra, struct device *dev) > > > > > > EXPORT_SYMBOL(mmc_alloc_host); > > > > > > +static void mmc_check_max_seg_size(struct mmc_host *host) > > > +{ > > > + unsigned int max_seg_size = dma_get_max_seg_size(mmc_dev(host)); > > > > Is dma_get_max_seg_size() really intended to be called for any struct > > device (representing the mmc controller) like this? > > > > My understanding is that the dma_get_max_seg_size() is supposed to be > > called by using the DMA engine device, no? > > Oh good catch sounds like I'm calling it for the wrong device, > need to check. In that case sounds like this can't be generic? No, I don't think so as it's only the mmc host driver that knows about the DMA engine device. 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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, 29 Nov 2018 at 20:13, Tony Lindgren wrote: > > * Ulf Hansson [181119 12:09]: > > On 31 October 2018 at 16:57, Tony Lindgren wrote: > > > With CONFIG_DMA_API_DEBUG_SG a device may produce the following warning: > > > > > > "DMA-API: mapping sg segment longer than device claims to support" > > > > > > We default to 64KiB if a DMA engine driver does not initialize dma_parms > > > and call dma_set_max_seg_size(). This may be lower that what many MMC > > > drivers do with mmc->max_seg_size = mmc->max_blk_size * mmc->max_blk_count. > > > > > > Let's do a sanity check for max_seg_size being higher than what DMA > > > supports in mmc_add_host() and lower it as needed. > > > > > > Cc: Kishon Vijay Abraham I > > > Cc: Peter Ujfalusi > > > Cc: Russell King > > > Reported-by: Russell King > > > Signed-off-by: Tony Lindgren > > > --- > > > drivers/mmc/core/host.c | 16 ++++++++++++++++ > > > 1 file changed, 16 insertions(+) > > > > > > diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c > > > --- a/drivers/mmc/core/host.c > > > +++ b/drivers/mmc/core/host.c > > > @@ -13,6 +13,7 @@ > > > */ > > > > > > #include > > > +#include > > > #include > > > #include > > > #include > > > @@ -415,6 +416,19 @@ struct mmc_host *mmc_alloc_host(int extra, struct device *dev) > > > > > > EXPORT_SYMBOL(mmc_alloc_host); > > > > > > +static void mmc_check_max_seg_size(struct mmc_host *host) > > > +{ > > > + unsigned int max_seg_size = dma_get_max_seg_size(mmc_dev(host)); > > > > Is dma_get_max_seg_size() really intended to be called for any struct > > device (representing the mmc controller) like this? > > > > My understanding is that the dma_get_max_seg_size() is supposed to be > > called by using the DMA engine device, no? > > Oh good catch sounds like I'm calling it for the wrong device, > need to check. In that case sounds like this can't be generic? No, I don't think so as it's only the mmc host driver that knows about the DMA engine device. Kind regards Uffe _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel