From mboxrd@z Thu Jan 1 00:00:00 1970 From: miquel.raynal@bootlin.com (Miquel Raynal) Date: Fri, 29 Jun 2018 09:40:35 +0200 Subject: [PATCH v3 01/17] platform-msi: allow creation of MSI domain without interrupt number In-Reply-To: References: <20180622151432.1566-1-miquel.raynal@bootlin.com> <20180622151432.1566-2-miquel.raynal@bootlin.com> Message-ID: <20180629094035.5199fe89@xps13> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Marc, Marc Zyngier wrote on Thu, 28 Jun 2018 12:12:04 +0100: > On 22/06/18 16:14, Miquel Raynal wrote: > > platform_msi_alloc_priv_data() checks that a number of interrupts is > > always given. This extra-check has no real impact and just prevents > > uselessly the user to create an MSI tree domain: remove it. > > > > Signed-off-by: Miquel Raynal > > --- > > drivers/base/platform-msi.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/base/platform-msi.c b/drivers/base/platform-msi.c > > index 60d6cc618f1c..9f001f4ccc0f 100644 > > --- a/drivers/base/platform-msi.c > > +++ b/drivers/base/platform-msi.c > > @@ -203,7 +203,7 @@ platform_msi_alloc_priv_data(struct device *dev, unsigned int nvec, > > * accordingly (which would impact the max number of MSI > > * capable devices). > > */ > > - if (!dev->msi_domain || !write_msi_msg || !nvec || nvec > MAX_DEV_MSIS) > > + if (!dev->msi_domain || !write_msi_msg || nvec > MAX_DEV_MSIS) > > return ERR_PTR(-EINVAL); > > > > if (dev->msi_domain->bus_token != DOMAIN_BUS_PLATFORM_MSI) { > > > > Huh... It's not that simple. > > Yes, it allows you to get a tree via platform_msi_create_device_domain > (assuming that's why you're changing it -- your commit message doesn't > say much) Indeed. That was exactly my intention. > but it also has some impact on the way msi_domain_prepare_irqs > works (see how it is called from platform_msi_create_device_domain). > > Importantly, the msi_prepare callback takes nvec as a parameter, and > that ends up trickling down to the irqchip, or whatever will setup the > MSI domain. Things like the GICv3 ITS do rely on that to carve out the > LPI space that subsequently gets used to populate the domain. > > So no, you can't do it like that. If you really want a tree, add a > helper that does so. So if I understand correctly, what should be done is writting a new helper that would do something similar to platform_msi_create_device_domain(), but creating instead a tree domain and still giving msi_domain_prepare_irqs() a meaningful number (as nvec) that would be the maximum number of MSIs that could be allocated. Am I right here? Thanks, Miqu?l